10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-K

(Mark One)

þ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2014

OR

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from             to             

Commission file number: 000-51567

NxStage Medical, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware	04-3454702
(State or Other Jurisdiction of Incorporation or Organization)	(I.R.S. Employer Identification No.)
350 Merrimack Street, Lawrence, MA	01843
(Address of Principal Executive Offices)	(Zip Code)

Registrant’s Telephone Number, Including Area Code:

(978) 687-4700

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class	Name of Each Exchange on Which Registered
Common Stock, $0.001 par value	Nasdaq Global Select Market

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  þ      No  ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    Yes  ¨      No  þ

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  þ      No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  þ      No  ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.    ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act:

Large accelerated filer  þ       Accelerated filer  ¨ Non-accelerated filer  ¨ Smaller reporting company  ¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨      No  þ

The aggregate market value of common stock held by non-affiliates of the registrant was approximately $870 million, as of June 30, 2014, based on the last reported sale price of the registrant’s common stock on the NASDAQ Global Select Market on June 30, 2014.

There were 62,707,290 shares of the registrant’s common stock outstanding as of the close of business on February 17, 2015.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive proxy statement for its 2015 Annual Meeting of Stockholders are incorporated by reference in response to Part III of this report.

NXSTAGE MEDICAL, INC.

2014 ANNUAL REPORT ON FORM 10-K

TABLE OF CONTENTS

			Page
PART I
	Item 1.	Business		5
	Item 1A.	Risk Factors		33
	Item 1B.	Unresolved Staff Comments		54
	Item 2.	Properties		54
	Item 3.	Legal Proceedings		55
	Item 4.	Mine Safety Disclosures		55
PART II
	Item 5.	Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities		56
	Item 6.	Selected Financial Data		58
	Item 7.	Management’s Discussion and Analysis of Financial Condition and Results of Operations		59
	Item 7A.	Quantitative and Qualitative Disclosures about Market Risk		75
	Item 8.	Financial Statements and Supplementary Data		76
	Item 9.	Changes in and Disagreements with Accountants on Accounting and Financial Disclosure		107
	Item 9A.	Controls and Procedures		107
	Item 9B.	Other Information		110
PART III
	Item 10.	Directors, Executive Officers and Corporate Governance		110
	Item 11.	Executive Compensation		110
	Item 12.	Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters		110
	Item 13.	Certain Relationships and Related Transactions, and Director Independence		110
	Item 14.	Principal Accounting Fees and Services		110
PART IV
	Item 15.	Exhibits, Financial Statement Schedules		111
SIGNATURES				112
Exhibit Index				113

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CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This report and certain information incorporated by reference herein contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 concerning our business, operations and financial condition, including statements with respect to:

• our market opportunity and the market adoption of our products in the U.S. and internationally;

• the growth of the home and critical care markets;

• access to home and more frequent hemodialysis;

• plans to continue expanding internationally;

• the development and commercialization of new products and improvements to existing products;

• regulatory submissions and approvals;

• sales to our key customers, including DaVita HealthCare Partners Inc. and Fresenius Medical Care;

• the adequacy of our funding;

• expectations with respect to future demand for our products and revenue growth and the components of such revenue growth;

• the timing, scope and success of our initiatives to improve our gross profit as a percentage of revenues;

• improvements in certain segment cash flows and profitability and other operational and financial metrics;

• our manufacturing operations and supply chain;

• availability of suitable facilities;

• our plans to open and operate NxStage Kidney Care dialysis centers;

• planned investments in marketing and research and development;

• expectations with respect to our expenses and working capital levels and requirements;

• changes in deferred revenue;

• changes with respect to our expenses as a percentage of revenues;

• achieving our business plan;

• global economic conditions;

• product recalls;

• expectations with respect to achieving positive operating margins, positive cash flows and profitable operations;

• volatility of our stock price;

• retention of earnings;

• product cost reduction plans;

• expectations with respect to product reliability;

• manufacturing dialyzers for sale to Asahi Kasei Kuraray Medical Co.;

• our ability to withstand supply chain disruptions;

• the scope of patent protection with respect to our products;

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• the availability of, and changes in, reimbursement for home and more frequent hemodialysis, including home nocturnal hemodialysis; and

• the financial, commercial and operational impact of any of the above.

All statements other than statements of historical facts included in this Annual Report regarding our strategies, prospects, financial condition, costs, plans and objectives are forward-looking statements. When used in this report, the words “expect”, “anticipate”, “intend”, “plan”, “believe”, “seek”, “estimate”, “potential”, “continue”, “predict”, “may”, “will” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Because these forward-looking statements involve risks and uncertainties, actual results could differ materially from those expressed or implied by these forward-looking statements.

Readers should carefully review the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” set forth in this report, as these sections describe important factors that could cause actual results to differ materially from those indicated by our forward-looking statements. We undertake no obligation to revise or update publicly any forward-looking statement.

NOTE REGARDING TRADEMARKS

NxStage^®, Streamline^®, ButtonHole^®, MasterGuard^® and Fingershield^® are registered trademarks of NxStage Medical, Inc. PureFlow SL^TM and System One^TM are trademarks of NxStage Medical, Inc.

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PART I

For convenience, in this Annual Report, “NxStage,” “we,” “us,” and “the Company” refer to NxStage Medical, Inc. and our consolidated subsidiaries, taken as a whole.

Item 1. Business

Overview

We are a medical device company that develops, manufactures and markets innovative products for the treatment of kidney failure, fluid overload and related blood treatments and procedures. Our primary product, the System One, was designed to satisfy an unmet clinical need for a system that can deliver the therapeutic flexibility and clinical benefits associated with traditional dialysis machines in a smaller, portable, easy-to-use form that can be used by healthcare professionals and trained lay users alike in a variety of settings, including patient homes, as well as more traditional care settings such as hospitals and dialysis centers. Given its design, the System One is particularly well-suited for home hemodialysis and a range of dialysis therapies including more frequent dialysis and nocturnal dialysis, which clinical literature suggests provides patients better clinical outcomes and improved quality of life. The System One is cleared or approved for commercial sale in the U.S., Canada and certain other markets, and is CE marked in the EU, for the treatment of acute and chronic kidney failure and fluid overload. The System One is cleared specifically by the U.S. Food and Drug Administration (FDA) for home hemodialysis and home nocturnal hemodialysis, as well as therapeutic plasma exchange in a clinical environment. The System One is also CE marked in the EU for home nocturnal hemodialysis. In February 2013, we received CE Mark approval and in April 2013 we received clearance from the FDA for the new high flow capabilities with the System One. We began selling the System One with this feature to both U.S. customers and international distributors in 2014. We also sell, through our Medisystems subsidiary, blood tubing sets and needles primarily to dialysis centers for the treatment of end-stage renal disease (ESRD). These products are cleared or approved for commercial sale in the U.S., Canada and certain other markets and are CE marked in the EU. We believe our largest market opportunity is for the System One used in the home dialysis market for the treatment of ESRD. We operate a small number of NxStage Kidney Care dialysis centers focused on supporting home therapy and providing flexible in-center options with NxStage technology as part of our market development activities to increase home therapy access. We continue to make significant investments in marketing, research and development, and these dialysis centers, all of which are intended to help us to further penetrate and expand the market for our products.

ESRD, which affects over 630,000 people in the U.S. and 2 million people worldwide, is an irreversible, life-threatening loss of kidney function that is treated predominantly with dialysis. Dialysis is a kidney replacement therapy that removes toxins and excess fluids from the bloodstream and, unless the patient receives a kidney transplant, is required for the remainder of the patient’s life. Approximately 70% of ESRD patients in the U.S. rely on life-sustaining dialysis treatment. Hemodialysis, the most widely prescribed type of dialysis, typically consists of treatments in a dialysis clinic three times per week, with each session lasting three to five hours. Approximately 11% of U.S. ESRD dialysis patients receive dialysis treatment at home, mostly through self-treatment with peritoneal dialysis, although surveys of physicians and healthcare professionals suggest that a larger proportion of patients could take responsibility for their own care. We believe that approximately 10-15% of the over 440,000 U.S. ESRD patients currently receiving dialysis treatment would be appropriate candidates for home hemodialysis with the NxStage System One. Clinical data also suggests that hemodialysis therapy administered five or six times per week, commonly referred to as more frequent therapy, including more frequent nocturnal therapy, better mimics the natural functioning of the human kidney and can lead to improved clinical outcomes, including lower mortality, significant improvements in left ventricular mass, reductions in antihypertensive medications, reduced fluid overload, reduced depression and improvements in health-related quality of life. We believe there is an unmet need for a hemodialysis system that allows more frequent, nocturnal and easily administered therapy at home, as well as in other settings, and we have designed our system to address this and other kidney replacement markets. Given the clinical and quality of life benefits associated with more frequent hemodialysis therapy, nearly all of our System One patients in the home market receive treatment five or six times a week.

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Measuring a little over a foot tall, the System One is the smallest and only portable commercially available hemodialysis system. It consists of a compact, portable and easy-to-use cycler, disposable drop-in cartridge and high purity premixed fluid. The System One has a self-contained design and simple user interface making it easy to operate by a trained patient and trained care partner in any setting prescribed by the patient’s physician, including while the patient is sleeping. Unlike traditional dialysis systems, our System One does not require any special disinfection and its operation does not require specialized electrical or plumbing infrastructure or modifications to the home. Patients can bring the System One home, plug it into a conventional electrical outlet and operate it, thereby eliminating what can be expensive plumbing and electrical household modifications required by other traditional dialysis systems. Because of its portability, patients also have the freedom to travel with the System One. We market the System One to dialysis clinics for chronic home hemodialysis treatment. The clinics in turn provide the System One to ESRD patients.

We also market the System One to hospitals for treatment of acute kidney failure and fluid overload. It is estimated that there are over 200,000 cases of acute kidney failure in the U.S. each year. The clinical flexibility of our System One, coupled with its ease-of-use and portability, make our system well suited for hospital critical care environments.

In addition to the System One, we sell a line of extracorporeal disposable products that are primarily used for in-center dialysis treatments for patients with ESRD. These products include hemodialysis blood tubing sets, arteriovenous (AV) fistula needles and apheresis needles. Our main blood tubing set product line is Streamline which is designed to provide certain clinical and operational benefits. Our needle products line includes AV fistula needles, which incorporate safety features including MasterGuard technology, and ButtonHole needles.

For the year ended December 31, 2014, our revenues were $301.5 million and we incurred a net loss of $24.3 million. As of December 31, 2014, we had cash and cash equivalents of $52.9 million, total assets of $309.7 million and total stockholders’ equity of $191.6 million. We have operated at a loss since our inception in 1998. At December 31, 2014, we had an accumulated deficit of approximately $387.5 million.

We have continued to make improvements in our gross margins for our products; however, we cannot provide assurance that our gross margins will continue to improve or, if they do improve, the rate at which they will improve. Continued improvements in gross margins for our System One and In-Center segments are dependent on many factors, including growing revenues, reducing costs of revenues by lowering manufacturing costs, implementing design and process improvements, obtaining better purchasing terms and prices, and increasing reliability of our products. Additionally, we expect our operating expenses to continue to increase as we continue to invest in selling and marketing, research and development and NxStage Kidney Care, our Services segment. We expect that the combined profitability of the System One and In-Center segments will improve as we continue to leverage our existing operating infrastructure; however, our continued investment in NxStage Kidney Care will offset these improvements and negatively impact our near-term profitability.

We expect to make continued improvements in the combined cash flows associated with our System One and In-Center segments. In addition, we have spent and expect to continue to spend cash to establish NxStage Kidney Care dialysis centers. We believe, based on current projections and the current nature of our business, that we have the required resources to fund our ongoing operating requirements, which include selling and marketing activities to increase public awareness in the System One, our research and development activities to develop new products and enhance our existing products, and our planned investments in NxStage Kidney Care. If we determine that additional investments in these or any other initiatives would be beneficial, we may choose to access the credit or capital markets to provide additional liquidity.

We were incorporated in Delaware in 1998 under the name QB Medical, Inc., and later changed our name to NxStage Medical, Inc. Our principal executive offices are located at 350 Merrimack Street, Lawrence, Massachusetts 01843.

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Additional financial information regarding our business segments and geographic data about our assets is contained in Management’s Discussion and Analysis of Financial Condition and Results of Operations in Item 7, and in our Notes to Consolidated Financial Statements included in Item 8, of this Annual Report.

Our Products

The System One

Our primary product, the System One, is a small, portable, easy-to-use hemodialysis system. Sales of the System One and related products accounted for approximately 71%, 67% and 67% of our total sales for the years ended December 31, 2014, 2013 and 2012, respectively.

The System One uses the following components:

• The NxStage Cycler.    A compact portable electromechanical device containing pumps, control mechanisms, safety sensors and remote data capture functionality.

• The NxStage Cartridge.    A single-use, disposable, integrated treatment cartridge that loads simply and easily into the cycler. The cartridge incorporates a proprietary volumetric fluid management system and includes a pre-attached dialyzer.

• Premixed Dialysate.    The System One uses high-purity premixed dialysate for hemodialysis applications. The volume of fluids used varies with treatment options, prescription, and setting. We supply our premixed dialysate in sterile five liter bags or through the use of our PureFlow SL accessory. The PureFlow SL module prepares dialysate fluid in the patient’s home using ordinary tap water and dialysate concentrate thereby reducing the need for bagged fluids for in-home treatments.

Streamline Blood Tubing Sets

Streamline blood tubing sets feature an efficient and airless design intended to enable providers to reduce treatment time and optimize dose delivery. Streamline also includes our patented LockSite needleless access sites, eliminating the need for sharp needles or costlier guarded needles to be used with the tubing set in connection with dialysis therapy. LockSite is intended to facilitate healthcare facility compliance with Occupational Safety and Health Administration bloodborne pathogens requirements to implement use of medical devices with engineered sharps-injury protection and needleless systems. Sales of our Streamline product accounted for approximately 17%, 20% and 19% of our total sales for the years ended December 31, 2014, 2013 and 2012, respectively.

AV Fistula and Apheresis Needles

Our AV fistula and apheresis needles have been designed to achieve a smooth blood flow throughout the treatment, intended to result in less clotting, lower pressure drops, and less stress on the patient’s blood. A significant amount of our needles sold are branded MasterGuard, and include our Fingershield anchor designed to protect the operator from inadvertent needle stick injury. We also offer ButtonHole needles for hemodialysis therapies as an alternative to our AV fistula needles with MasterGuard. ButtonHole needles are used by patients that employ “the constant-site technique”, whereby a fistula needle is inserted in the same place each treatment. Published clinical experience suggests that the incidence of pain, hematoma, and infiltrations at the needle insertion site can be reduced by utilizing the constant-site technique. Our ButtonHole AV fistula needle has an anti-stick, dull bevel design well-suited for the constant-site technique, while also being designed to reduce the risk of accidental needle sticks. Sales of needles accounted for approximately 8%, 10% and 11% of our total sales for the years ended December 31, 2014, 2013 and 2012, respectively.

Our Business by Segment

We have three reportable business segments: System One, In-Center and Services. We distribute our products in three markets: home, critical care and in-center.

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Our System One segment includes revenues from the sale and rental of the System One and PureFlow SL dialysate preparation equipment and the sale of disposable products in the home and critical care markets. The home market is devoted to the treatment of ESRD patients in the home or a home-like setting, while the critical care market is devoted to the treatment of hospital-based patients with acute kidney failure or fluid overload. Some of our largest customers in the home market provide outsourced renal dialysis services to some of our customers in the critical care market. Sales of product to both markets are made primarily through dedicated sales forces and distributed directly to the customer, or the patient, with certain products sold through distributors. The results of our international business are included in the System One segment.

Our In-Center segment includes revenues from the sale of blood tubing sets and needles for hemodialysis primarily for the treatment of ESRD patients at dialysis centers and needles for apheresis. Nearly all In-Center products are sold through national distributors.

Our Services segment includes revenues from dialysis services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

The remainder of our operations and financial information, included within the Other category, relates to the manufacturing of dialyzers for sale to Asahi Kasei Kuraray Medical Co. (Asahi) and research and development and general and administrative expenses that are excluded from the segment operating performance measures.

System One

We began marketing the System One to perform hemodialysis for ESRD patients in September 2004, and we began marketing our System One specifically for home use in July 2005, after the System One was cleared by the FDA for home hemodialysis. We market the System One to independent dialysis clinics as well as dialysis clinics that are part of national or regional chains, providing clinics with improved access to the developing home dialysis market. As Medicare regulations require that all chronic ESRD patients be under the care of a dialysis clinic, whether they are treated at home or in clinic, we do not sell the System One directly to patients. In February 2013, we received CE Mark approval and in April 2013 we received clearance from the FDA for the new high flow capabilities with the NxStage System One. We began selling the System One with this feature to both U.S. customers and international distributors in 2014.

For each month that a patient is treated with the System One, we bill the clinic for the purchase of the related disposable cartridges and treatment fluids necessary to perform treatment. A significant majority of System One equipment in the home market is purchased, rather than rented, by our customers including our two largest customers in the home market, DaVita HealthCare Partners (DaVita) and Fresenius Medical Care (Fresenius). Purchased equipment pricing includes service for an initial contractual period after which the customer pays a standard service fee for continued access to the service depot and the replacement service swap pool of equipment. After selling or renting a System One to a clinic, our clinical educators train the clinic’s nurses and dialysis technicians on the proper use of the System One using our proprietary training materials. We then rely on our customers’ trained technicians and nurses to train home patients, their care partners and other technicians and nurses using the System One. We are not responsible for and do not provide patient training except for NxStage Kidney Care patients.

Patient training takes place at the clinic primarily during the patient’s prescribed treatment sessions. Training typically takes three to four weeks and includes basic instruction on ESRD, the operation of the System One and the insertion by the patient or their care partner of needles into the patient’s vascular access site. Training sessions are reimbursed at a fixed rate by Medicare and private insurance.

The System One cycler sold to hospitals in the critical care market is based on the same technology platform used in the home market but has additional features that offer a wider range of therapies, including therapeutic plasma exchange, and includes an additional display module, called OneView, which is designed to facilitate easier medical record charting and troubleshooting. We also sell related disposable cartridges and treatment fluids necessary to perform dialysis treatment in the critical care market. Most of our customers in the critical

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care market use our System One to perform prolonged or continuous renal replacement therapy for their acute kidney failure or fluid overload patients. We are specifically focusing our sales efforts in the critical care market on those large institutions that we believe are most dedicated to prolonged or continuous renal replacement therapy for patients with acute kidney failure and believe in ultrafiltration as an earlier-stage treatment option for fluid overload.

After selling or renting a System One to a hospital, our clinical educators generally train the hospital’s intensive care unit and acute dialysis nurses on the proper use of the System One using our proprietary training materials. We then rely on the trained nurses to train other nurses. By adopting this “train the trainer” approach, our sales nurses do not need to return to the hospital each time a new nurse requires training. We also sell one- and two-year service contracts following the expiration of our standard one-year warranty period for System One hardware. We sell a bio-medical training program, whereby we train bio-medical engineers on how to service and repair certain aspects of the System One in the critical care setting.

Our customers in the System One segment are highly consolidated. DaVita and Fresenius own and operate the two largest chains of dialysis clinics in the U.S. and collectively provide treatment to more than two-thirds of U.S. dialysis patients. DaVita and Fresenius are our two largest customers in the System One segment.

During 2014, 2013 and 2012, direct sales to DaVita represented 30%, 32% and 31% of our System One segment revenues, respectively, and direct sales to Fresenius represented 22%, 20% and 17% of our System One segment revenues, respectively. Furthermore, DaVita and Fresenius are our largest customers in the home market, with approximately 40% and 30%, respectively, of our home hemodialysis patients. Increased sales to DaVita and Fresenius have driven a large portion of our historical revenue growth and will be important to future growth. If the purchasing patterns of either of these customers adversely change, including in response to our initiative to establish NxStage Kidney Care dialysis centers, our business could be negatively affected.

Our agreement with DaVita for the U.S. home hemodialysis market extends through December 31, 2015, and thereafter automatically extends on a monthly basis unless terminated by us or DaVita. Our agreement with Fresenius for the U.S. home hemodialysis market extends through December 31, 2016, with monthly renewals thereafter unless terminated by us or Fresenius.

In-Center

We sell primarily blood tubing sets and needles to customers in the in-center market. In this market, our customers are independent dialysis clinics as well as dialysis clinics that are part of national or regional chains. Although in many instances we have direct contractual relationships with our customers, nearly all of our sales in this market are made through national distributors in order to leverage national networks, shipping efficiencies and existing customer relationships. We plan our manufacturing and distribution activities based on distributor purchase orders. Finished goods are shipped directly to distributor warehouses. We support distributor selling and marketing efforts with brand marketing support and a team of clinical educators who assist with clinical in-service activities.

Our In-Center segment revenues are highly concentrated in several significant purchasers. Our two largest distributors are Gambro AB and Henry Schein, Inc. Revenues from Gambro represented 36%, 37% and 36% of our In-Center segment revenues during 2014, 2013 and 2012, respectively. Revenues from Henry Schein represented 30%, 32% and 34% of our In-Center segment revenues during 2014, 2013 and 2012, respectively. Our distribution agreement with Gambro extends through December 31, 2015, with annual renewals thereafter unless terminated by us or Gambro. Our distribution agreement with Henry Schein expires on April 25, 2015, and we are negotiating the terms of a new distribution agreement with Henry Schein.

DaVita has been a significant customer in the In-Center segment. Sales of our products through distributors to DaVita accounted for approximately half of In-Center segment revenues during 2014, 2013 and 2012. In-Center segment sales are expected to decrease as a result of DaVita’s needle purchase agreement expiring in

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December 2014. DaVita continues to have purchase commitments for our blood tubing sets pursuant to an agreement with Gambro. Currently, DaVita’s product supply agreement with Gambro requires DaVita to purchase a significant majority of its blood tubing set requirements from Gambro, and our distribution agreement with Gambro requires Gambro to exclusively supply our blood tubing sets to DaVita.

Services

We operate a small number of NxStage Kidney Care dialysis centers focused on supporting home therapy and providing flexible in-center options with NxStage technology as part of our market development activities to increase home therapy access.

International

We sell the System One and certain other products internationally, through a combination of direct sales to hospitals and dialysis centers and sales through distributors. Products sold to distributors are shipped directly to distributor warehouses and the distributors sell or rent our products to dialysis providers or hospitals and are responsible for marketing, clinic training and equipment servicing and repair. To date, our international sales have been limited, and we are still very early in our international commercialization efforts.

Marketing, Customer Support

We have a sales force that calls on dialysis clinics, nephrologists and hospitals. In addition to specialized sales representatives, we also employ nurses in our sales force as clinical educators to support our sales efforts. We have a staff of customer support specialists to assist patients, clinics and hospitals with product orders and deliveries. We also provide technical support 24 hours a day, seven days a week through a dedicated staff of technical support representatives, to respond to questions raised by patients, clinics and hospitals concerning the System One. Our marketing activities also include utilizing direct mail and internet campaigns to provide product literature and clinically relevant information, advertising in trade publications, sponsoring educational programs for dialysis patients and clinicians, and participating in nephrology conferences. Our direct sales efforts focus almost exclusively on the home and critical care markets as we rely heavily on distributors to sell our products in the in-center market.

In the home market we use a depot service model for equipment servicing and repair while we generally service equipment sold to customers in the critical care market in the field. For our home market customers, if a device requires repair, we arrange for a replacement device to be shipped to the site of care, whether it is a patient’s home or a clinic, and for pick up and return to us of the system requiring service. This shipment is done by common carrier, and, as there are no special installation requirements, the patient or clinic can quickly and easily set up the new machine. The nature of the hospital critical care settings, coupled with the practices of other intensive care unit dialysis equipment suppliers, necessitates an option for on-site support for our systems installed in this environment, or for the use of a trained bio-medical engineer.

Competition

The dialysis therapy market is mature, consolidated and competitive. Our business faces a high degree of competition from larger, more established companies with greater financial and human resources.

Products

Our System One in the critical care market competes against products from Gambro, a subsidiary of Baxter International, Inc., Fresenius, B. Braun Medical, Inc. and others. Our product lines in the in-center market compete directly against products produced by Fresenius, Nipro Medical Corporation, B. Braun, Baxter together with its subsidiary Gambro, JMS Co. Ltd. and others. Our competitors in each of these markets sell one or more FDA-cleared medical devices for the treatment of acute or chronic kidney failure. Each of these competitors offer

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products that have been in use for a longer time than our System One and are more widely recognized by physicians, patients and providers. These competitors have significantly more financial and human resources, more established sales, service and customer support infrastructures and spend more on product development and marketing than we do. Many of our competitors also have established relationships with the providers of dialysis therapy, including Fresenius which operates a chain of dialysis centers. The product lines of most of these companies are broader than ours, enabling them to offer a broader bundle of products, and have established sales forces and distribution channels that may afford them a significant competitive advantage.

We believe the competition in the market for kidney dialysis equipment and supplies is based primarily on:

• product quality;

• ease-of-use;

• cost effectiveness;

• sales force coverage; and

• clinical flexibility and performance.

Our System One is currently the only portable system specifically indicated for home hemodialysis and home nocturnal hemodialysis in the U.S. Presently, no other product has an indication for home nocturnal hemodialysis in the U.S. There is a non-portable product on the market with a home clearance in the U.S., and a number of other products that are under development and may be released in the next several years, that are, or will be, competitive to our System One in the home market.

In 2011, Fresenius, our second largest customer in the System One segment, with nearly all of those sales in the home market, obtained clearance for its 2008K@home hemodialysis system for use in home chronic therapy. Fresenius has indicated that it is seeking clearance for its sorbent technology within the critical care setting. Fresenius has also suggested that it would seek clearance for its Portable Artificial Kidney to market in the U.S. for in-center use.

Baxter obtained CE marking for a new home hemodialysis system in the EU in December 2013 and has discussed its plans for a near-term European launch. Baxter has also discussed plans to complete additional clinical studies and file for regulatory approval for a home nocturnal hemodialysis indication in the U.S.

Other small companies are also working to develop products for this market. We are unable to predict when, if ever, any of these products may attain regulatory clearance and appear in the market, or how successful they may be should they be introduced, but the introduction of additional viable products to the home market could adversely affect our sales and growth.

For the critical care market, we believe we compete favorably in terms of product quality and ease of use due to our System One design, portability, drop-in cartridge and use of premixed fluids. We believe we also compete favorably on the basis of clinical flexibility, given the System One’s ability to perform hemofiltration, hemodialysis and ultrafiltration. We believe we compete favorably in terms of cost-effectiveness for hospitals that perform continuous renal replacement therapies. In the fluid overload market, which is a very small component of our critical care market, drug therapy is currently the most common and preferred treatment. To date, ultrafiltration has not been broadly adopted and, if the medical community does not accept ultrafiltration as clinically useful, cost-effective and safe, we will not be able to successfully compete against existing pharmaceutical therapies and other device-based technologies in the treatment of fluid overload.

For the in-center market, where we sell blood tubing sets and needles, we believe that we compete favorably in terms of product quality, ease-of-use, cost effectiveness, clinical flexibility and performance. We also compete favorably in terms of branding, as our subsidiary Medisystems has been selling products to dialysis centers for the treatment of ESRD since 1981. We compete unfavorably in terms of sales force coverage, as we rely nearly exclusively on distributors rather than our own direct sales force.

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Our primary competitors are large, well-established businesses with significantly more financial and human resources and greater commercial infrastructures than ours. We believe our ability to compete successfully will depend largely on our ability to:

• continuously improve our products and develop and obtain clearance for new products;

• establish the infrastructures necessary to support a growing home, critical care and in-center dialysis products business;

• maintain and improve product quality;

• continue to develop sales and marketing capabilities; and

• achieve cost reductions.

Our ability to successfully market our products for the treatment of kidney failure could also be adversely affected by pharmacological and technological advances in preventing the progression of chronic ESRD and/or in the treatment of acute kidney failure, technological developments by others in the area of dialysis, the development of new medications designed to reduce the incidence of kidney transplant rejection and progress in using kidneys harvested from genetically-engineered animals as a source of transplants. These pharmacological or technological advancements and competitive pressures in general may adversely affect our business.

Services

The U.S. dialysis services industry is highly competitive, with providers of varying sizes vying for patients, medical directors and employees. We believe the ability of our NxStage Kidney Care dialysis centers to be successful and attract patients in local markets will depend on our ability to effectively educate the local patient and physician community on the benefits of the therapies offered at these dialysis centers while continuing to deliver a high level of quality care at cost-effective rates.

Clinical Experience and Results

Significant clinical literature strongly supports that daily or more frequent hemodialysis therapy can lead to improved clinical outcomes, including lower mortality, reduced cardiovascular hospitalizations, reduction in left ventricular mass, reduction in hypertension and use of antihypertensive medications, improved nutritional status, and overall improvement in quality of life, including improvements related to overall physical and mental health, depressive symptoms, sleep, restless legs syndrome and post-dialysis recovery time.

In early 2006, we enrolled the first patient in our post-market FREEDOM (Following Rehabilitation, Economics, and Everyday Dialysis Outcome Measurements) study, which is designed to quantify the clinical and economic benefits of daily home therapy administered to Medicare patients with the System One versus conventional thrice-weekly dialysis. The FREEDOM study is a prospective, multi-center, observational study of 501 Medicare patients in over 41 clinical centers. The study compares Medicare patients using the System One with a matched cohort of patients from the U.S. Renal Data System, or USRDS, a database of patients treated with traditional in-center thrice weekly dialysis, to help define differences in the cost of care and patient outcomes between the daily home setting and the dialysis clinic setting. Comparing the study group of patients using the System One to a USRDS database group matched in terms of demographics, co-morbidities, geography, number of years on dialysis and other key factors should allow a valuable comparison to be made without the time and cost challenges of a crossover study, in which patients would be followed for a given time on each type of therapy.

Interim four and twelve month results from our ongoing FREEDOM study show daily home hemodialysis treatment made possible by the System One therapy significantly improves select measures of patient quality-of-life as compared to conventional, thrice-weekly in-center treatment. Specific improvements identified to date include a reduction in post-dialysis recovery time (the average time to resume normal activity), returning significant quality time to patients each week. Other benefits include a reduction in depressive symptoms,

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improvements in select physical and mental health quality of life factors, a reduction in antihypertensive medications, improvements in sleep and restless legs syndrome and improvements in overall quality of life and physical intimacy. These results have been published in major peer review journals including the Journal of the American Society of Nephrology, the American Journal of Kidney Disease, and Kidney International.

In a NxStage-funded study of Medicare patients starting NxStage home hemodialysis therapy from 2005-2007 compared to traditional in-center dialysis patients during the same period, risk of death was found to be significantly lower, and three-year survival significantly higher, in the NxStage population versus the matched in-center hemodialysis cohort. This study was published in the Journal of the American Society of Nephrology in early 2012.

In another NxStage-funded study of Medicare patients starting NxStage home hemodialysis therapy from 2007 to mid-2010 compared to peritoneal dialysis patients during the same period, risks of death, hospitalization, and therapy attrition were found to be significantly lower in the NxStage population versus the matched peritoneal dialysis cohort. This was the first matched cohort study of its kind comparing home dialysis modalities.

The Frequent Hemodialysis Network (FHN) Trial Group (2010) conducted a randomized clinical trial to determine whether increasing hemodialysis frequency would result in beneficial changes in left ventricular mass, self-reported physical health, and other intermediate outcomes among patients undergoing maintenance hemodialysis. Patients were randomly assigned to undergo hemodialysis six times per week (frequent hemodialysis, 125 patients) or three times per week (conventional hemodialysis, 120 patients) for 12 months. The investigators concluded that frequent hemodialysis, as compared with conventional hemodialysis, was associated with favorable results with respect to the composite outcomes of death or change in left ventricular mass and death or change in a physical-health composite score, but prompted more frequent interventions related to vascular access.

During 2014, we completed an approved Investigational Device Exemption, or IDE, clinical study intended to support a home nocturnal indication for the System One, and in December 2014, the FDA cleared the System One to perform home nocturnal hemodialysis. Presently, no other product is cleared to perform home nocturnal hemodialysis in the U.S.

In addition to the FREEDOM and nocturnal studies, we have completed two significant clinical trials with the System One for ESRD therapy: a post-market study of chronic daily hemofiltration and a study under an FDA-approved IDE. We have also completed a study of ultrafiltration with the System One for fluid overload associated with congestive heart failure.

In the IDE study, we compared center-based and home-based daily dialysis with the System One. That study was a prospective, multi-center, two-treatment, two-period, open-label, cross-over study. The first phase of the study consisted of 48 treatments, six per week, in an eight-week period performed in-center, while the second phase consisted of the same number of treatments performed in an in-home setting. Between the two phases, there was a two-week transition period conducted primarily in the patient’s home. Prior to study initiation, enrolled patients were to have been on at least two weeks of daily hemodialysis with the System One in an in-center environment. The objective of the study was to evaluate equivalence on a per-treatment basis between the delivery of hemodialysis with our system in-center and at home. The result of the investigation showed that the safety and effectiveness of hemodialysis with our system was equivalent in each setting.

Research and Development

Our research and development organization has focused on developing innovative technical approaches that address the limitations of current dialysis systems and disposable products. Our development team has skills across the range of technologies required to develop and maintain dialysis systems and products. These areas include filters, tubing sets, mechanical systems, fluids, software and electronics. In response to physician and

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patient feedback and our own assessments, we are continually working on enhancements to our product designs to improve ease-of-use, functionality, reliability and safety and to reduce product cost. In addition, we are engaged in development activities focused around our next generation systems, including a system for peritoneal dialysis. We also seek to develop new products that supplement our existing product offerings and intend to continue to actively pursue research and development opportunities for complementary products.

In June 2013, we entered into a research and development program sponsored by the Defense Advanced Research Projects Agency (DARPA) to develop an innovative new device to treat sepsis. This program aligns well with our technology and supports our next generation product development.

For the years ended December 31, 2014, 2013 and 2012, we incurred research and development expenses of $22.6 million, $18.9 million and $17.1 million, respectively.

Intellectual Property

We seek to protect our investment in the research, development, manufacturing and marketing of our products through the use of patent, trademark, copyright and trade secret law. We own rights to a number of patents, trademarks, copyrights, trade secrets and other intellectual property directly related and important to our business both in the U.S. and abroad. We also have domestic and foreign pending patent applications.

Patents for individual products extend for varying periods of time according to the date a patent application is filed or a patent is granted and the term of the patent protection available in the jurisdiction granting the patent. The scope of protection provided by a patent can vary significantly from country to country.

The following table lists all of our issued U.S. and international patents as of December 31, 2014.

Patent No.	Regime	Title	Expiration Date
5643190	US	Flow-Through Treatment Device		1/17/2015
5704924	US	Easy Use Needle Protector Sheath		1/11/2016
5772624	US	Reusable Blood Lines		7/20/2015
5772638	US	Protector For Needle		9/17/2016
5817043	US	Flow-Through Treatment Device		1/17/2015
5895368	US	Blood Set Priming Method And Apparatus		9/23/2016
5951870	US	Automatic Priming Of Blood Sets		10/21/2017
5980741	US	Bubble Trap With Flat Side Having Multipurpose Supplemental Ports		8/1/2017
5983947	US	Docking Ports For Medical Fluid Sets		3/3/2017
6042570	US	Needle Point Protection Sheath		2/11/2019
6051134	US	Bubble Trap Having Common Inlet/Outlet Tube		3/28/2017
6089527	US	Squeeze Clamp For Flexible Tubing		10/3/2017
6113062	US	Squeeze Clamp		1/28/2019
6117342	US	Bubble Trap With Directed Horizontal Flow And Method Of Using		11/26/2016
6165149	US	Reusable Blood Lines		7/20/2015
6177049	US	Reversing Flow Blood Processing System		6/10/2018
6187198	US	Automatic Priming Of Blood Sets		10/21/2017
6193694	US	Needle Point Protection Sheath		2/11/2019
6196519	US	Squeeze Clamp For Flexible Tubing		10/3/2017
6206954	US	Blood Set And Chamber		5/13/2018
6299589	US	Flow-Through Treatment Method		1/17/2015
6440095	US	Pump Segment Having Connected, Parallel Branch Line		12/31/2015
6290665	US	Blood Set Priming Method And Apparatus		9/23/2016

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Patent No.	Regime	Title	Expiration Date
6319465	US	Reversing Flow Blood Processing System Having Reduced Clotting Potential		6/3/2019
6344139	US	Arterial and Venous Blood Tubing Set		10/21/2017
6387069	US	Blood Set Priming Method And Apparatus		9/23/2016
6464878	US	Automatic Priming Of Blood Sets		10/21/2017
6517508	US	Set For Blood Processing		11/3/2019
6517522	US	Tubular Intravenous Set		4/3/2020
6554789	US	Layered Fluid Circuit Assemblies And Methods For Making Them		2/14/2017
6572576	US	Method And Apparatus For Leak Detection In A Fluid Line		7/7/2021
6579253	US	Fluid Processing Systems And Methods Using Extracorporeal Fluid Flow Panels Oriented Within A Cartridge		2/14/2017
6582385	US	Hemofiltration System Including Ultrafiltrate Purification And Re-Infusion System		2/19/2018
6589482	US	Extracorporeal Circuits For Performing Hemofiltration Employing Pressure Sensing Without An Air Interface		2/14/2017
6595943	US	Systems And Methods For Controlling Blood Flow And Waste Fluid Removal During Hemofiltration		2/14/2017
6595965	US	Needle Protector Sheath		7/15/2017
6596234	US	Reversing Flow Blood Processing System		3/14/2019
6616635	US	Tubular Intravenous Set		4/3/2020
6620119	US	Reusable Blood Lines		11/12/2015
6638478	US	Synchronized Volumetric Fluid Balancing Systems And Methods		2/14/2017
6649063	US	Devices for Sterile-Filtering Fluid and Methods of Use		10/7/2021
6666839	US	Reusable Blood Lines		7/20/2015
6673314	US	Interactive Systems And Methods For Supporting Hemofiltration Therapies		2/14/2017
6685680	US	Tapered Intravenous Cannula		4/20/2019
6695807	US	Blood Flow Reversing System		1/18/2022
6743193	US	Hermetic Flow Selector Valve		7/17/2021
6755801	US	Dialysis Pressure Monitoring With Clot Suppression		11/8/2019
6830553	US	Blood Treatment Systems And Methods That Maintain Sterile Extracorporeal Processing Conditions		2/14/2017
6852090	US	Fluid Processing Systems And Methods Using Extracorporeal Fluid Flow Panels Oriented Within A Cartridge		12/10/2017
6955655	US	Hemofiltration System		10/7/2017
6979309	US	Systems And Methods For Performing Blood Processing And/Or Fluid Exchange Procedures		6/19/2017
7004924	US	Methods, Systems, And Kits For The Extracorporeal Processing Of Blood		10/19/2018
7025744	US	Injection Site For Male Luer Or Other Tubular Connector		8/12/2023
7025750	US	Set For Blood Processing		11/3/2019
7040142	US	Method And Apparatus For Leak Detection In Blood Circuits Combining External Fluid Detection And Air Infiltration Detection		2/9/2022
7056308	US	Medical Device With Elastomeric Penetrable Wall And Inner Seal		11/1/2022
7087033	US	Method And Apparatus For Leak Detection In A Fluid Line		8/23/2022
7112273	US	Volumetric Fluid Balance Control For Extracorporeal Blood Treatment		10/2/2024
7147613	US	Measurement Of Fluid Pressure In A Blood Treatment Device		8/29/2020
7166084	US	Blood Set Priming Method And Apparatus		7/22/2017
7214312	US	Fluid Circuits, Systems, And Processes For Extracorporeal Blood Processing		7/8/2022

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Patent No.	Regime	Title	Expiration Date
7226538	US	Fluid Processing Apparatus		1/21/2022
7267658	US	Renal Replacement Therapy Device For Controlling Fluid Balance Of Treated Patient		3/6/2021
7300413	US	Blood Processing Machine And System Using Fluid Circuit Cartridge		5/4/2021
7337674	US	Pressure Detector For Fluid Circuits		12/13/2025
7338460	US	Blood Processing Machine Fluid Circuit Cartridge		6/19/2021
7347849	US	Modular Medical Treatment Replaceable Component		10/7/2022
7419597	US	Fluid, Circuits, Systems, And Processes For Extracorporeal Blood Processing		7/12/2021
7470265	US	Dual Access Spike For Infusate Bags		1/11/2024
7473238	US	Hemofiltration Systems And Methods That Maintain Sterile Extracorporeal Processing Conditions		8/11/2020
7544300	US	Batch Filtration System For Preparation Of Sterile Fluid For Renal Replacement Therapy		1/7/2024
7569047	US	Medical Device With Elastomeric Penetrable Wall		11/11/2024
7588684	US	Systems And Methods For Handling Air And/or Flushing Fluids In A Fluid Circuit		7/13/2021
7591804	US	Short-Winged Needle And Guard		12/20/2026
7686778	US	Waste Balancing For Extracorporeal Blood Treatment Systems		7/7/2026
7749393	US	Batch Filtration System For Preparation Of Sterile Fluid For Renal Replacement Therapy		1/7/2024
7758082	US	Fluid Line Connector Safety Device		5/5/2028
7771379	US	Functional Isolation Of Upgradeable Components To Reduce Risk In Medical Treatment Devices		7/16/2025
7776001	US	Registration Of Fluid Circuit Components In A Blood Treatment Device		10/28/2023
7776219	US	Methods, Devices, And Systems For Hemodilution		8/11/2021
7780619	US	Blood Treatment Apparatus		11/29/2019
7790043	US	Systems And Methods For Handling Air And/Or Flushing Fluids In A Fluid Circuit		7/13/2021
7892208	US	Medical Tubing Set Sheath		6/12/2028
7901579	US	Blood Treatment Dialyzer/Filter For Permitting Gas Removal		3/1/2026
7976711	US	Batch Filtration System For Preparation Of Sterile Fluid For Renal Replacement Therapy		1/7/2024
8002727	US	Methods And Apparatus For Leak Detection In Blood Processing Systems		9/24/2026
8042838	US	Fluid Line Connector Safety Device		12/5/2027
8092414	US	Diaphragm Pressure Pod For Medical Fluids		12/12/2029
8190651	US	System And Method For Identifying And Pairing Devices		12/4/2029
8192387	US	Last-Chance Quality Check And/Or Air/Pathogen Filter For Infusion Systems		10/29/2024
8202420	US	Batch Filtration System For Preparation Of Sterile Fluid For Renal Replacement Therapy		1/7/2024
8210049	US	Pressure Measurement Device		5/4/2031
8235931	US	Waste Balancing For Extracorporeal Blood Treatment Systems		2/10/2025
8251973	US	Medical Devices And Methods For Assisting In Sub-Scab Access		2/20/2029
8377039	US	Injection Site For Male Luer Or Other Tubular Connector		9/9/2028
8460228	US	Methods, Devices, And Systems For Parallel Control Of Infusion Device		1/9/2031
8460558	US	Batch Filtration System For Preparation Of Sterile Fluid For Renal Replacement Therapy		1/7/2024
8469331	US	Filtration System For Preparation Of Fluids For Medical Applications		5/21/2030

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Patent No.	Regime	Title	Expiration Date
8480608	US	Methods And Apparatus For Leak Detection In Blood Processing Systems		1/16/2025
8491518	US	Diaphragm Pressure Pod For Medical Fluids		1/9/2026
8496625	US	Safe Needle Methods, Apparatus, And Systems		10/20/2031
8506536	US	Medical Devices And Methods For Assisting In Sub-Scab Access		12/12/2030
8545428	US	Filtration System For Preparation Of Fluids For Medical Applications		1/7/2024
8585096	US	Fluid Line Safety Device		10/26/2030
8608658	US	Method And Apparatus For Machine Error Detection By Combining Multiple Sensor Inputs		1/4/2022
8641615	US	Method And Apparatus For Machine Error Detection By Combining Multiple Sensor Inputs		1/4/2022
8647312	US	Injection Site For Male Luer Or Other Tubular Connector		10/4/2022
8641684	US	Closure For Tubular Access Port		5/15/2029
8679348	US	Filtration System For Preparation Of Fluids For Medical Applications		11/28/2024
8876777	US	Safe Needle Methods, Apparatus, And Systems		5/26/2031
8909613	US	System And Method For Identifying And Pairing Devices		3/10/2031
3809563	JP	Easy Use Needle Protector Sheath		12/20/2016
4118233	JP	Method And Apparatus For Leak Detection In A Fluid Line		7/8/2022
3843414	JP	Needle Protector Sheath		4/12/2025
4416368	JP	Fluid Processing Systems And Methods Using Extracorporeal Fluid Flow Panels Oriented Within A Cartridge		11/29/2020
4117505	JP	Flow-Through Treatment Device		1/16/2016
4387631	JP	Layered Fluid Circuit Assemblies And Methods For Making Them		11/29/2020
4416797	JP	Improved Methods And Apparatus For Leak Detection In Blood Processing Systems		11/5/2024
4734343	JP	Filtration System For Preparation Of Fluids For Medical Applications		1/9/2026
4739019	JP	Injection Site For Male Luer Or Other Tubular Connector		10/2/2023
5378203	JP	Filtration System For Preparation Of Fluids For Medical Applications		4/9/2027
1425063	IT	Method And Apparatus For Leak Detection In A Fluid Line		7/8/2022
1691882	IT	Apparatus For Leak Detection In Blood Processing System		11/5/2024
1838356	IT	Filtration System For Preparation Of Fluids For Medical Applications		1/9/2026
2012906	IT	Tubing Clamp For Medical Applications		4/9/2027
1235614	GB	Interactive Systems And Methods For Supporting Hemofiltration Therapies		1/19/2015
1414543	GB	Systems And Methods For Handling Air And/Or Flushing Fluids In A Fluid Circuit		7/8/2022
1425063	GB	Method And Apparatus For Leak Detection In A Fluid Line		7/8/2022
1531894	GB	Blood Treatment Machine Comprising An Air/Pyrogen Filter		6/5/2023
1592494	GB	Preparing Replacement Fluid		1/7/2024
1691882	GB	Apparatus For Leak Detection In Blood Processing System		11/5/2024
1838356	GB	Filtration System For Preparation Of Fluids For Medical Applications		1/9/2026
2012906	GB	Tubing Clamp For Medical Applications		4/9/2027
2505363	GB	Fluid Heating Apparatuses, Systems, And Methods		5/14/2032
1235614	FR	Interactive Systems And Methods For Supporting Hemofiltration Therapies		11/29/2020
1425063	FR	Method And Apparatus For Leak Detection In A Fluid Line		7/8/2022
1691882	FR	Apparatus For Leak Detection In Blood Processing System		11/5/2024
1838356	FR	Filtration System For Preparation Of Fluids For Medical Applications		1/9/2026
2012906	FR	Tubing Clamp For Medical Applications		4/9/2027

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Patent No.	Regime	Title	Expiration Date
60045621.8	DE	Fluid Processing Systems And Methods Using Extracorporeal Fluid Flow Panels Oriented Within A Cartridge		11/29/2020
60047429.1	DE	Interactive Systems And Methods For Supporting Hemofiltration Therapies		11/29/2020
602004021672.0	DE	Preparing Replacement Fluid		1/7/2024
60245474.3	DE	Systems And Methods For Handling Air And/Or Flushing Fluids In A Fluid Circuit		7/8/2022
60341758.2	DE	Blood Treatment Machine Comprising An Air/Pyrogen Filter		6/5/2023
602004029077.7	DE	Apparatus For Leak Detection In Blood Processing System		11/5/2024
602006017654.6	DE	Filtration System For Preparation Of Fluids For Medical Applications		1/9/2026
60043710.8-08	DE	Synchronized Volumetric Fluid Balancing Systems And Methods		11/29/2020
602007008395.8	DE	Tubing Clamp For Medical Applications		4/9/2027
60237621.1	DE	Methods And Apparatus For Leak Detection In A Fluid Line		7/8/2022
2153091	CA	Needle Protector Sheath		6/30/2015
2530440	CA	Medical Device With Elastomeric Penetrable Wall And Inner Seal		6/28/2024
2593580	CA	Filtration System For Preparation Of Fluids For Medical Applications		1/9/2026
000023148-0001	EU	Blood Treatment Machine And Parts Thereof		4/1/2028
1235614	EP	Interactive Systems And Methods For Supporting Hemofiltration Therapies		11/29/2020
1425063	EP	System For Leak Detection In A Fluid Line		7/8/2022
1531894	EP	Blood Treatment Machine Comprising An Air/Pyrogen Filter		6/5/2023

In addition to the issued patents and pending patent applications owned by us, in the U.S. and select non-U.S. markets, we possess trade secrets and proprietary know-how relating to our products. Any of our trade secrets, know-how or other technology not protected by a patent could be misappropriated, or independently developed by, a competitor and could, under some circumstances, be used to prevent us from further use of such information, know-how or technology.

Our strategy is to develop patent portfolios for our research and development projects. We monitor the activities of our competitors and other third parties with respect to their use of intellectual property. We intend to aggressively defend the patents we hold, and we intend to vigorously contest claims other patent holders may bring against us.

The medical device industry is characterized by the existence of a large number of patents and frequent litigation based on allegations of patent infringement. While we attempt to ensure that our products and methods do not infringe other parties’ patents and proprietary rights, our competitors may assert that our products, or the methods that we employ, are covered by patents held by them. In addition, our competitors may assert that future products and methods we may market infringe their patents.

We require our employees, consultants and advisors to execute confidentiality agreements with us. We also require our employees to agree to disclose and assign to us all inventions conceived by them during their employment with us. Similar obligations are imposed upon consultants and advisors performing work for us relating to the design or manufacture of our products. Despite efforts to protect our intellectual property, unauthorized parties may attempt to copy aspects of our products or obtain and use information that we regard as proprietary.

Manufacturing

The manufacture of our products is accomplished through a complementary combination of outsourcing and internal production. We have manufacturing facilities in Mexico, Germany and Italy. At our facility in Tijuana,

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Mexico, we manufacture System One equipment and disposables and In-Center bloodlines, and we service System One equipment. We manufacture our dialyzer filters at a facility in Germany owned by Asahi and operated by us, and we perform molding activities at our facility in Italy. We outsource the manufacture of premixed dialysate, needles and some components.

We depend upon a number of single-source suppliers for certain of our raw materials, components and finished goods, including the fiber used in our System One filters, our needles, premixed dialysate and sterile bags, as well as sterilization services. Finding alternative sources for these raw materials, components, finished goods and sterilization services would be difficult and in many cases entail a significant amount of time, disruption and cost. Where obtaining a second source is more difficult, we have tried to establish supply agreements that better protect our continuity of supply, although we do not have supply agreements with all of our single-source suppliers. Where we have no agreements in place, we work, to the extent economically feasible, to maintain enough inventory of the single-sourced component to allow us to, if needed, satisfy our requirements for the component while we secure an alternative source of supply. Some of our most critical single-source supply relationships are with Membrana and Laboratorios PiSA S.A. de C.V.

Membrana is our only supplier of the fiber used in our filters for System One products under an agreement that expires in December 2023, and contractually we cannot obtain an alternative source of fiber for our System One products. While our relationship with Asahi could afford us back-up supply in the event of supply disruptions at Membrana, we do not have the regulatory approvals necessary to use Asahi fiber in our System One cartridge in the U.S. and the performance of Asahi fiber in our System One has not yet been validated.

Laboratorios PiSA is our only supplier of premixed dialysate. Our supply agreement with Laboratorios PiSA extends through December 2019. We have committed to purchase from Laboratorios PiSA a minimum quantity of premixed dialysate over the term of the agreement. While we can purchase premixed dialysate from other qualified suppliers, any significant disruption in Laboratorios PiSA’s ability to supply premixed dialysate to us would impair our business, at least in the near-term.

Government Regulation

We are subject to government regulation in the countries in which we conduct business. In the U.S., numerous laws and regulations govern all the processes by which medical devices are brought to market and, for our NxStage Kidney Care dialysis centers, the manner in which we administer and submit claims for patient care. In the foreign countries in which we market and sell our products, we are subject to local regulations affecting, among other things, design and product standards, packaging and labeling and promotion requirements.

Food and Drug Administration

In the U.S., our products are subject to regulation by the FDA, which regulates our products as medical devices. The FDA regulates the design, development, clinical testing, manufacture, labeling, distribution, import and export, sale and promotion of medical devices. Noncompliance with applicable FDA requirements can result in, among other things:

• fines;

• injunctions;

• civil penalties;

• recall or seizure of products;

• total or partial suspension of production;

• failure of the government to grant pre-market clearance or pre-market approval for devices;

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• withdrawal of marketing clearances or approvals; and

• criminal prosecution.

Unless an exemption applies, all medical devices must receive either 510(k) clearance or pre-market approval (PMA) from the FDA before they may be commercially distributed in the U.S.

The FDA classifies medical devices into one of three classes:

• Class I devices, which are subject to only general controls (e.g., labeling, medical device reporting, and prohibitions against adulteration and misbranding) and, in some cases, to the 510(k) pre-market clearance requirements;

• Class II devices, generally requiring 510(k) pre-market clearance before they may be commercially marketed in the U.S.; and

• Class III devices, consisting of devices deemed by the FDA to pose the greatest risk, such as life-sustaining, life-supporting or implantable devices, or devices deemed not substantially equivalent to a predicate device, generally requiring submission of a PMA supported by clinical trial data.

In addition, the FDA can impose restrictions on the sale, distribution or use of devices at the time of their clearance or approval, or subsequent to marketing.

FDA Regulatory Clearance Status

We currently have all of the regulatory clearances required to market the System One in the U.S. in both the home and critical care markets. The FDA has cleared the System One for the treatment, under a physician’s prescription, of renal failure or fluid overload using hemofiltration, hemodialysis and/or ultrafiltration. The FDA has also specifically cleared the System One for both home hemodialysis and home nocturnal hemodialysis use under a physician’s prescription.

We received our first clearance from the FDA for a predecessor model to the System One in January 2001 for hemofiltration and ultrafiltration. In July 2003, we received expanded clearance from the FDA for the System One for hemodialysis, hemofiltration and ultrafiltration. In June 2005, we received FDA clearance specifically allowing us to promote home hemodialysis using the System One. In October 2010, we received FDA clearance for our therapeutic plasma exchange cartridge for use with the NxStage System One in a clinical environment. In February 2013, we received CE Mark approval and in April 2013 we received clearance from the FDA for the new high flow capabilities with the NxStage System One. We began selling the System One with this feature to both U.S. customers and international distributors in 2014. To date we have received 37 product clearances from the FDA since our inception in December 1998 for our System One and related products. We continue to seek opportunities for product improvements and feature enhancements, which will, from time to time, require FDA clearance before market launch.

We have received a total of 27 product clearances to market Medisystems products that support the in-center market. These clearances, the first of which was received in 1981, cover blood tubing sets used for hemodialysis, needle sets used in hemodialysis and apheresis, and other components such as intravenous administration sites, medics and transducer protectors, used primarily for hemodialysis.

FDA Clearance Procedures

510(k) Clearance Pathway.    When we are required to obtain a 510(k) clearance for a device that we wish to market, we must submit a pre-market notification to the FDA demonstrating that the device is substantially equivalent to (1) a device that was legally marketed prior to May 28, 1976 and for which the FDA has not yet required pre-market approval; (2) a device which has been reclassified from Class III to Class II or I; or (3) a

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novel device classified into Class I or II through de novo classification. If the FDA agrees that the device is substantially equivalent to the predicate, it will subject the device to the same classification and degree of regulation as the predicate device, thus effectively granting clearance to market it. The FDA attempts to respond to a 510(k) pre-market notification within 90 days of submission of the notification (or in some instances 30 days under what is referred to as a “special” 510(k) submission), but the response may be a request for additional information or data, sometimes including clinical data. As a practical matter, pre-market clearance can take significantly longer, including up to one year or more.

After a device receives 510(k) clearance for a specific intended use, any modification that could significantly affect its safety or effectiveness, or that constitutes a major change in its intended use, would require a new 510(k) clearance or could require pre-market approval. In the first instance, the manufacturer may determine that a change does not require a new 510(k) clearance. The FDA can review any such decision and can disagree with a manufacturer’s determination. If the FDA disagrees with a manufacturer’s determination that a new clearance or approval is not required for a particular modification, the FDA can require the manufacturer to cease marketing and recall the modified device until 510(k) clearance or pre-market approval is obtained.

Pre-market Approval Pathway.    A pre-market approval application must be submitted if the device cannot be cleared through the 510(k) process. The pre-market approval process is much more demanding than the 510(k) pre-market notification process. A pre-market approval application must be supported by extensive information including, but not limited to, technical data, preclinical and clinical trials, manufacturing details and labeling to demonstrate to the FDA’s satisfaction the safety and effectiveness of the device. After the FDA determines that a pre-market approval application is complete, the FDA accepts the application and begins an in-depth review of the submitted information. The FDA, by statute and regulation, has 180 days to review an accepted pre-market approval application, although the review generally occurs over a significantly longer period of time, and can take up to several years. During this review period, the FDA may request additional information or clarification of information already provided. Also during the review period, an advisory panel of experts from outside the FDA may be convened to review and evaluate the application and provide recommendations to the FDA as to the approvability of the device. In addition, the FDA will conduct a pre-approval inspection of the manufacturing facility to ensure compliance with the Quality System Regulations. New pre-market approval applications or supplemental pre-market approval applications are required for modifications that affect the safety or effectiveness of the device. These types of changes include changes to the manufacturing process, labeling, use and design of the approved device. PMA supplements often require submission of the same type of information as a pre-market approval application, except that the supplement is limited to information needed to support any changes from the device covered by the original pre-market approval application, and may not require as extensive clinical data or the convening of an advisory panel.

Clinical Trials.    A clinical trial is almost always required to support a pre-market approval application and is sometimes required for a 510(k) pre-market notification. Clinical trials for devices that involve significant risk, referred to as significant risk devices, require submission of an application for an IDE to the FDA. The IDE application must be supported by appropriate data, such as animal and laboratory testing results, showing that it is safe to test the device in humans and that the testing protocol is scientifically sound. Clinical trials for a significant risk device may begin once the IDE application is approved by the FDA and the institutional review board, or IRB, overseeing the clinical trial. If the FDA fails to respond to an IDE application within 30 days of receipt, the application is deemed approved, but IRB approval would still be required before a study could begin. Products that are not significant risk devices are deemed to be “non-significant risk devices” under FDA regulations, and are subject to abbreviated IDE requirements, including informed consent, IRB approval of the proposed clinical trial and submission of certain reports to the IRB. Clinical trials are subject to extensive recordkeeping and reporting requirements. Our clinical trials must be conducted under the oversight of an IRB at each clinical study site and in accordance with applicable regulations and policies including, but not limited to, the FDA’s good clinical practice requirements.

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Continuing FDA Regulation

After a device is placed on the market, numerous regulatory requirements apply. These include, among others:

• product listing and establishment registration, which helps facilitate FDA inspections and other regulatory action;

• Quality System Regulations, which require manufacturers to have a quality system for the design, manufacture, packaging, labeling, storage, installation, and servicing of finished medical devices;

• labeling regulations, which govern product labels and labeling, prohibit the promotion of products for unapproved, or off-label, uses and impose other restrictions on labeling and promotional activities;

• clearance of product modifications that could significantly affect safety or efficacy or that would constitute a major change in intended use of one of our cleared devices;

• medical device reporting, or MDR, regulations, which require that manufacturers report to the FDA if their device may have caused or contributed to a death or serious injury or malfunctioned in a way that would likely cause or contribute to a death or serious injury if it were to recur;

• the FDA’s recall authority, whereby it can ask, or under certain conditions order, device manufacturers to recall from the market a product that is in violation of governing laws and regulations;

• regulations pertaining to voluntary recalls; and

• notices of corrections or removals.

MDR Regulations.    The MDR regulations require that we report to the FDA any incident in which our product may have caused or contributed to a death or serious injury, or in which our product malfunctioned and, if the malfunction were to recur, would likely cause or contribute to a death or serious injury. To date, a majority of our MDR reports had been submitted to comply with the FDA’s blood loss policy for routine dialysis treatments. This policy, which is no longer in effect, required manufacturers to file MDR reports related to routine dialysis treatments if the patient experienced blood loss greater than 20cc.

FDA Inspections.    We have registered with the FDA as a medical device manufacturer. The FDA seeks to ensure compliance with regulatory requirements through periodic, unannounced facility inspections and these inspections may include the manufacturing facilities of our subcontractors. Failure to comply with applicable regulatory requirements can result in enforcement action by the FDA, which may include any of the following:

• warning letters or untitled letters;

• fines, injunctions, and civil penalties;

• administrative detention, which is the detention by the FDA of medical devices believed to be adulterated or misbranded;

• voluntary or mandatory recall or seizure of our products;

• customer notification, or orders for repair, replacement or refund;

• operating restrictions, partial suspension or total shutdown of production;

• refusal to review pre-market notification or pre-market approval submissions;

• rescission of a substantial equivalence order or suspension or withdrawal of a pre-market approval; and

• criminal prosecution.

The FDA has inspected our Lawrence, Massachusetts facility and quality system multiple times. In our first inspection, one observation was made, but was rectified during the inspection, requiring no further response from

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us. Our subsequent inspections, including our most recent inspection in January 2013, resulted in no inspectional observations. Medisystems has been inspected by the FDA on multiple occasions, and all inspections resulted in no action indicated. We cannot provide assurance that we can maintain a comparable level of regulatory compliance in the future at our facilities.

Foreign Regulation of Medical Devices

We are also subject to regulations in the foreign countries in which we market and sell our products. We currently have limited sales outside of the U.S. Foreign regulations, which may vary substantially from country to country, relate to, among other things, product standards, packaging, labeling and promotion requirements, import restrictions, tariff regulations, duties and tax requirements.

Clearance or approval of our products by regulatory authorities comparable to the FDA, or in the case of the EU the affixing of the CE mark, may be necessary in foreign countries prior to marketing the product in those countries, whether or not FDA clearance has been obtained. The regulatory requirements for medical devices vary significantly from country to country. They can involve requirements for additional testing and may be time consuming and expensive. We cannot provide assurance that we will be able to obtain regulatory approvals in any other markets or be able to affix the CE mark to new products in the EU.

In the specific case of the EU, manufacturers of medical devices are required to conduct an assessment of the conformity of the devices with the Essential Requirements found in Annex I to Council Directive 93/42/EEC of 14 June 1993 concerning medical devices, commonly known as the Medical Devices Directive, and to affix a CE Mark to these devices prior to marketing these within the EU. The Essential Requirements govern the quality, safety and performance of the medical devices. The classification of individual medical devices will determine whether the participation by a notified body in the conformity assessment process will be necessary. Notified bodies are private organizations that are licensed by the competent authorities of individual EU Member States to conduct conformity assessment procedures and to verify the conformity of manufacturers and their medical devices with the Essential Requirements.

If, where the participation by a notified body is necessary, the outcome of the conformity assessment procedure is positive the notified body will issue a related CE Certificate of Conformity. The manufacturer of the device will then complete the technical file for the medical device and, after having prepared and signed a related Declaration of Conformity, affix the CE mark to the product.

Demonstration of conformity of medical devices and their manufacturers with the Essential Requirements laid down in Annex I of the Medical Devices Directive must be based, among other things, on the evaluation of clinical data supporting the safety and performance of the products during normal conditions of use. Where necessary, this will include evaluation of clinical data generated in clinical investigations conducted with the medical devices. Conduct of clinical investigations in the EU is governed by detailed regulatory obligations. These include the requirement of prior authorization of the investigation by the competent authorities of the EU Member States in which the investigation takes place and the requirement to obtain a positive opinion concerning the investigation protocol from a competent Ethics Committee. The conduct of clinical investigations in the EU can be expensive and challenging and the outcome of such investigations is uncertain. There are no guarantees that the data generated in the clinical investigation would be sufficient to support CE marking of the medical device. Moreover, the clinical investigation may be suspended or discontinued by the competent authorities of the EU Member States or on the advice of the Ethics Committee.

The Medical Devices Directive requires manufacturers to maintain a Technical File related to their products. Manufacturers must also comply with quality system requirements set forth in the Annexes to the Medical Devices Directive. Such compliance can be facilitated by, among other things, a certificate of compliance with ISO 13485:2003. Through compliance with the ISO 13485:2003 standard, manufacturers benefit from a presumption of conformity with the relevant quality system requirements laid down in the Annexes to Medical Devices Directive.

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CE Certificates of Conformity have been issued in relation to all of our products that require such certificates and we have affixed a CE mark to these products. However, if we introduce any substantial change to any of our CE marked medical devices in the EU this may require an additional conformity assessment process in relation to the substantial changes and modification or preparation of new CE Certificates of Conformity and Declarations of Conformity. “Substantial changes” include the introduction of a new intended purpose for the medical device, a change in its design or a change in the device quality management system. There is little guidance concerning modifications that should be considered a substantial change. As the manufacturer of the medical device we would have sole responsibility for determining whether any modification constitutes a substantial change. There is a risk that the competent authorities of the EU Member States or our notified body may disagree with our assessment of the changes introduced to our products. The competent authorities of the EU Member States or our notified body may also come to a different conclusion than the FDA concerning any change made to our products.

In the EU we must comply with a number of regulatory requirements for products that have been CE marked and placed on the market relating to:

• registration of medical devices;

• pricing and reimbursement of medical devices;

• establishment of post-marketing surveillance and adverse event reporting procedures;

• field safety corrective actions, including product recalls and withdrawals;

• marketing and promotion of medical devices; and

• interactions with physicians.

Failure to comply with these requirements may result in enforcement measures being taken by the competent authorities of the EU Member States. These can include fines, administrative penalties, compulsory product withdrawals, injunctions and criminal prosecution. Such enforcement measures would have an adverse effect on the marketing of our products in the EU and, consequently, on our business and financial position.

The System One cycler and related cartridges are regulated as medical devices in Canada under the Canadian Medical Device Regulations and in the EU under the Medical Device Directive. We have received four product licenses from Canada. We have conducted a conformity assessment and affixed the CE mark in the EU to our System One and associated ancillaries.

Our blood tubing sets, AV fistula needles, apheresis needles, and other ancillary products are regulated as medical devices in Canada under the Canadian Medical Device Regulations and in the EU under the Medical Device Directive. We maintain six Medical Device Licenses in Canada under the Medisystems brand name for these products. We have conducted a conformity assessment and affixed the CE mark in the EU for AV fistula needles, apheresis needles, and other ancillary products.

Fraud and Abuse Laws

U.S. federal healthcare laws apply when our customers and NxStage Kidney Care dialysis centers submit claims for items or services that are reimbursed under Medicare, Medicaid, or other federally-funded healthcare programs. The principal federal fraud and abuse laws include: (1) the Anti-Kickback Statute, which prohibits the offer or payment of any remuneration for the purpose of inducing or rewarding referrals of items or services reimbursable by a federal healthcare program; (2) the False Claims Act, which prohibits the submission of false or otherwise improper claims for payment to a federally-funded healthcare program; and (3) criminal healthcare fraud statutes that prohibit false statements and improper claims to any third-party payors. There are often similar state anti-kickback and false claims laws that apply to state-funded Medicaid and other healthcare programs, as well as to private third-party payors. In addition, the U.S. Foreign Corrupt Practices Act can be used to prosecute companies in the U.S. for arrangements with physicians or other parties outside the U.S. if the physician or party is a government official of another country and the arrangement violates the laws of that country.

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Similar laws are increasingly being introduced in the individual EU Member States. The provision of benefits or advantages to physicians to induce or encourage the prescription, recommendation, endorsement, purchase, supply, order or use of medical devices is prohibited. The provision of benefits or advantages to physicians is also governed by the national anti-bribery laws of the EU Member States. One such example is the UK Bribery Act. Payments made to physicians in certain EU Member States must also be publicly disclosed. Moreover, agreements with physicians must often be the subject of prior notification and approval by the physician’s employer or competent professional organization or the competent authorities of the individual EU Member States. These requirements are provided in the national laws, industry codes or professional codes of conduct applicable in the EU Member States. Failure to comply with these requirements could result in reputational harm, public reprimands, administrative penalties, fines or imprisonment.

Anti-Kickback Statutes

The federal healthcare program Anti-Kickback Statute, and similar state laws, prohibit payments and other forms of remuneration that are intended to induce health care professionals or others either to refer patients or to purchase, lease, order or arrange for or recommend the purchase, lease or order of healthcare products or services. Other laws prohibit remuneration intended to induce patients to select a particular provider of services, including for dialysis. A number of states have enacted laws that require pharmaceutical and medical device companies to monitor and report payments, gifts and other remuneration made to physicians and other health care professionals and health care organizations. In addition, some state statutes, most notably laws in Massachusetts and Vermont, impose outright bans on certain manufacturer gifts to physicians. Some of these laws, referred to as “aggregate spend” or “gift” laws, carry substantial fines if they are violated. The federal Physician Payments Sunshine Act was enacted by Congress in 2010 as part of the comprehensive health care reform legislation, and the implementing regulations, released in February 2013, require us to collect and report certain data on payments and other transfers of value to physicians and teaching hospitals annually to the Centers for Medicare and Medicaid Services (CMS) for public reporting. It is widely anticipated that public reporting under the Sunshine Act will result in increased scrutiny of the financial relationships between industry, physicians and teaching hospitals.

The Anti-Kickback Statute is broad and potentially prohibits many arrangements and practices that are lawful in businesses outside of the healthcare industry. Recognizing that the Anti-Kickback Statute is broad and may technically prohibit many innocuous or beneficial arrangements, the Office of Inspector General of the Department of Health and Human Services, or OIG, issued a series of regulations, known as the safe harbors, beginning in July 1991. These safe harbors set forth provisions that, if all the applicable requirements are met, will assure healthcare providers and other parties that they will not be prosecuted under the Anti-Kickback Statute. The failure of a transaction or arrangement to fit precisely within a safe harbor does not necessarily mean that it is illegal or that prosecution will be pursued. However, conduct and business arrangements that do not fully satisfy an applicable safe harbor may result in increased scrutiny by government enforcement authorities such as the OIG. If scrutinized, arrangements that implicate the Anti-Kickback Statute, and that do not fall within a safe harbor, are analyzed by the OIG and other enforcement authorities on a case-by-case basis.

Government officials have focused recent enforcement efforts on, among other things, the sales and marketing activities of medical device manufacturers and other healthcare companies, and recently have brought cases against individuals or entities with personnel who allegedly offered unlawful inducements to potential or existing customers in an attempt to procure their business. Judgments and settlements of these cases by healthcare companies have involved significant fines and, in some instances, criminal pleas and convictions.

In addition to the federal Anti-Kickback Statute, many states have their own anti-kickback laws. Often, these laws closely follow the language of the federal law, although they do not always have the same exceptions or safe harbors. In some states, these anti-kickback laws apply with respect to all payors, including commercial health insurance companies.

The national legislation of many foreign countries includes provisions equivalent in content and consequences to the federal Anti-Kickback Statute and the Sunshine Act.

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False Claims Laws

Federal false claims laws prohibit any person from knowingly presenting, or causing to be presented, a false claim for payment to the federal government or knowingly making, or causing to be made, a false statement to get a false claim paid. Our NxStage Kidney Care dialysis centers are directly subject to these laws with respect to the reimbursement claims they file with government payors. In addition, medical device manufacturers can be held liable under false claims laws, even if they do not submit claims to the government, if they are found to have caused the submission of false claims, including through arrangements that violate the Anti-Kickback Statute. The federal False Claims Act also includes whistleblower provisions that allow private citizens to bring suit against an entity or individual on behalf of the U.S. and to recover a portion of any monetary recovery. Many of the recent highly publicized settlements in the healthcare industry related to the sales and marketing practices of pharmaceutical and medical device manufacturers have been cases brought under the False Claims Act. Violations of The Ethics in Patient Referrals Act, commonly known as the Stark Act, can also form the basis for False Claims Act liability. The Stark Act generally prohibits a physician from referring a patient to an entity for certain designated health services payable by Medicare or Medicaid when the physician has a financial relationship with the entity, such as an investment interest or a medical directorship. While outpatient dialysis services and most drugs furnished by our NxStage Kidney Care dialysis centers are excluded from the Stark Act’s prohibitions on self-referrals, certain outpatient prescription drugs may be subject to the Stark Act.

The majority of states also have statutes or regulations similar to the federal false claims laws, which apply to items and services reimbursed under Medicaid and other state programs. Several states have false claims laws that apply regardless of the payor. Sanctions under these federal and state laws may include civil monetary penalties, exclusion of a manufacturer’s products from reimbursement under government programs, criminal fines and imprisonment.

The national legislation of many foreign countries includes provisions equivalent in content and consequences to the federal false claims laws.

Compliance Program

The healthcare laws and fraud and abuse laws applicable to our business are complex and subject to variable interpretations. We maintain certain compliance review, education and training and other programs to further our commitment to high standards of ethical and legal conduct and to minimize the likelihood that we would engage in conduct or enter into arrangements in violation of applicable authorities. For example, we have (1) established a compliance team consisting of representatives from our Legal, Finance, Human Resources, Regulatory Affairs/Quality Assurance and Commercial departments that meets regularly; (2) established a compliance hotline that permits our employees to report anonymously any compliance issues that may arise; and (3) instituted other safeguards intended to help prevent any violations of the applicable fraud and abuse laws and healthcare laws, and to remediate any situations that could give rise to violations. We also review our transactions and agreements, both past and present, with qualified legal counsel to help ensure they are compliant.

Through our compliance efforts, we constantly strive to structure our business operations and relationships with our customers to comply with all applicable legal requirements. However, many of the laws and regulations applicable to us are broad in scope and may be interpreted or applied by prosecutorial, regulatory or judicial authorities in ways that we cannot predict. Thus, it is possible that governmental entities or other third parties could interpret these laws differently or assert non-compliance with respect to one or more of our business operations and relationships. Moreover, the standards of business conduct expected of healthcare companies under these laws and regulations have become more stringent in recent years, even in instances where there has been no change in statutory or regulatory language. If a claim were asserted against us for alleged non-compliance with fraud and abuse laws or other healthcare laws, and we were not to prevail, possible penalties and sanctions could have a material effect on our financial condition and ability to conduct our operations.

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Privacy and Security

In the course of performing our business we obtain, from time to time, confidential patient health information. For example, we learn patient names and addresses when we ship our System One supplies and related products to home hemodialysis patients. We may learn patient names and be exposed to confidential patient health information when we provide training on our products to our customers’ staff. Our home hemodialysis patients may also call our customer service representatives directly and, during the call, disclose confidential patient health information. We also receive and maintain confidential patient health information in connection with the operation of our NxStage Kidney Care centers. U.S. federal and state laws protect the confidentiality of certain patient health information, in particular individually identifiable information, and restrict the use and disclosure of that information. At the federal level, the Department of Health and Human Services promulgated health information and privacy and security rules under the Health Insurance Portability and Accountability Act of 1996, as amended under the Health Information Technology for Economic and Clinical Health Act, or HIPAA. HIPAA and the rules promulgated thereunder require certain entities to comply with established standards, including standards regarding the privacy and security of protected health information known as the HIPAA Privacy and Security Rules and to provide notification following a data breach involving protected health information. We are subject to HIPAA with regard to certain aspects of our business. In addition, many other state and federal laws regulate the use and disclosure of health information, including state medical privacy laws, state breach notification laws, and federal and state consumer protection laws. In many cases, these laws are not necessarily preempted by HIPAA, particularly if they afford greater protection to the individual than does HIPAA. These various laws may be subject to varying interpretations by courts and government agencies creating potentially complex compliance issues for our business.

We are also subject to laws and regulations in foreign countries covering the privacy and other regulation of health and employee information that may be more onerous than corresponding U.S. laws. These regulations may require that we obtain individual consent before we collect or process any personal data, restrict our use or transfer of personal data, impose technical and organizational measures to ensure the security of personal data, and require that we notify regulatory agencies, individuals or the public about any data securities breaches. As we expand our international operations, we may be required to expend significant time and resources to put in place additional mechanisms to ensure compliance with multiple data privacy laws. Failure to comply with these laws may result in significant fines and other administrative penalties and harm our business.

Reimbursement

Home and In-Center Markets

Medicare regulations require that all chronic ESRD patients be under the care of a dialysis clinic, whether they are treated at home or in-clinic. We sell or rent our System One and sell our needles and blood tubing sets to dialysis clinics. These clinics, in turn, are reimbursed by Medicare, Medicaid and private insurers. According to the 2014 USRDS Annual Data Report, Medicare or Medicaid is the primary payor for approximately 83% of prevalent dialysis patients using hemodialysis and peritoneal dialysis. The report also indicates that approximately 6% of patients are covered by commercial insurance with Medicare as the secondary payor, with the remaining 11% of patients classified by the USRDS as “other” or “unknown.” Certain centers have indicated that more frequent home hemodialysis therapy with the System One attracts a higher percentage of commercial insurance patients than other forms of dialysis.

Medicare.    Medicare generally provides health insurance coverage for persons who are age 65 or older and for persons who are completely disabled. For ESRD patients, however, Medicare coverage is not dependent on age or disability. Patients are eligible for Medicare based solely on ESRD. Coverage for patients eligible for Medicare based solely on ESRD begins on the first day of the fourth month after the patient begins dialysis treatments. During the three-month waiting period either Medicaid, private insurance or the patient is responsible for payment for dialysis services. Medicare waives this waiting period for individuals who participate in a home dialysis training program, or are hospitalized for a kidney transplant and the surgery occurs within a specified time period.

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For ESRD patients under age 65 who have any employer group health insurance coverage, regardless of the size of the employer or the individual’s employment status, Medicare coverage is generally secondary to the employer coverage during the 30-month period that follows the establishment of Medicare eligibility or entitlement based on ESRD. During this period, the patient’s existing insurer is responsible for paying primary benefits at the rate specified in the plan, which may be a negotiated rate or the healthcare provider’s usual and customary rate. As the secondary payor during this period, Medicare will make payments up to the applicable Medicare payment rate for dialysis services to supplement any primary payments by the employer group health plan if the plan covers the services but pays only a portion of the charge for the services.

Medicare generally is the primary payor for ESRD patients after the 30-month coordination period. Under current rules, Medicare is also the primary payor for ESRD patients during the 30-month period under certain circumstances. Medicare remains the primary payor when an individual becomes eligible for Medicare on the basis of ESRD if (1) the individual was already age 65 or over or was eligible for Medicare based on disability and (2) the individual’s private insurance coverage is not by reason of current employment or, if it is, the employer has fewer than 20 employees (in the case of eligibility by reason of age) or fewer than 100 employees (in the case of eligibility by reason of disability). The rules regarding entitlement to primary Medicare coverage when the patient is eligible for Medicare on the basis of both ESRD and age, or disability, have been the subject of frequent legislative and regulatory changes and there can be no assurance that these rules will not be unfavorably changed in the future.

When Medicare is the primary payor for services furnished by dialysis clinics, it reimburses dialysis clinics for 80% of the allowable rate, leaving the secondary insurance or the patient responsible for the remaining 20%.

As a result of legislation passed by the U.S. Congress more than 30 years ago, Medicare provides broad and well established reimbursement in the U.S. for ESRD. Effective January 1, 2011, CMS implemented a new prospective payment system for dialysis treatment. Under the new ESRD prospective payment system, CMS makes a single bundled payment to the dialysis facility for each dialysis treatment that covers all renal dialysis services and home dialysis and includes certain drugs (including erythropoiesis stimulating agents, iron and Vitamin D). The prospective payment system replaced the former system, which paid facilities a composite rate for a defined set of items and services, while paying separately for dugs, laboratory tests, and other services that were not included in the composite rate. With a vast majority of U.S. ESRD patients covered by Medicare, the Medicare reimbursement rate is an important factor in a potential customer’s decision to use the System One or our other products and limits the fees for which we can sell or rent our products. Additionally, current CMS rules limit the number of hemodialysis treatments paid for by Medicare to three times a week, unless there is medical justification provided by the dialysis facility based on information from the patient’s physician for additional treatments. Most patients using the System One in the home treat themselves, with the help of a care partner, up to six times per week. To the extent that Medicare contractors elect not to pay for additional treatments, adoption of the System One would likely be impaired and revenues from our Kidney Care dialysis centers likely would be reduced.

Medicare has been consolidating the Medicare contractors that process and pay Medicare claims. Accordingly, there have been and may continue to be changes in the contractors that determine medical justification for dialysis treatments. This change in the reviewing entity for Medicare claims could lead to a change in whether a customer receives Medicare reimbursement for additional treatments. If an adverse change to historical payment practices occurs, adoption of our System One in the home market may be impaired and revenues from our Kidney Care dialysis centers likely would be reduced.

Based on an analysis of historical Medicare payment files by the University of Michigan Kidney Epidemeology and cost Center, those delivering more frequent dialysis at home receive reimbursement, on average, for 1.5 times the number of treatments per month versus conventional dialysis, although this amount varies by jurisdiction. This variance arises from Medicare contractor policies, as well as from varying center billing practices. Currently, only three of the Medicare contractor jurisdictions have formal Local Coverage Determinations (LCDs); the majority have not issued a LCD and thus make coverage determinations on a case-

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by-case basis. As there is no consistent national standard for obtaining medical justification, a clinic’s decision as to how much it is willing to spend on home dialysis equipment and services will be at least partly dependent on the level of confidence the center has in the predictability of receiving reimbursement from Medicare for additional treatments per week based on submitted claims for medical justification.

Although access to home and more frequent hemodialysis continues to grow, we believe that current Medicare reimbursement policies lead to adoption rates lower than rates commensurate with the percentage of patients experts believe can perform and medically benefit from this therapy. We believe more predictable Medicare reimbursement for more frequent dialysis with less administrative burden, including further improving Medicare reimbursement for home hemodialysis training, would allow adoption of home hemodialysis at rates more consistent with what is deemed to be appropriate by the medical community. These beneficial changes, however, may never materialize.

A stated goal of the ESRD prospective payment system was to encourage home dialysis. To date, it has not had a positive impact on the adoption of home or more frequent hemodialysis or the price for which we can sell our products. However, the prospective payment system has had a significant positive impact on the adoption of peritoneal dialysis as evidenced by the significantly increased training rates for peritoneal dialysis. We believe this increased focus on peritoneal dialysis growth and peritoneal dialysis training has been to the detriment of home hemodialysis training rates, as home training resources, including home training nurses in particular, have been more devoted to peritoneal dialysis training, leaving less time for home hemodialysis training. CMS increased the payment rate for home dialysis training by 50% effective January 1, 2014. We do not know yet what effect this increase will have on use of home hemodialysis.

As part of the American Taxpayer Relief Act of 2012, Congress instructed the Centers for Medicare and Medicaid Services to recalculate the base payment rate under the prospective payment system for services furnished in 2014 and thereafter to account for changes in utilization of renal dialysis drugs since the prospective payment system was implemented. In response, the Centers for Medicare and Medicaid Services enacted a 12% reduction to the base payment rate to be implemented over a three- to four-year transition period, with overall payments for 2014 remaining unchanged. However, the Protecting Access to Medicare Act of 2014 replaced this phased-in reduction with reductions to the annual inflation adjustment to the base rate (known as the “market basket adjustment”) in 2015–2018. As a result, there is no reduction to the market basket adjustment in 2015, and the reduction is 1.25 percentage points in 2016 and 2017, and 1 percentage point in 2018. The effect of this change on the adoption of home and more frequent hemodialysis is not yet known.

Since April 1, 2013, Medicare payments to providers and suppliers for dialysis and related services have been reduced by 2% due to the automatic spending cuts (known as “sequestration”) required by U.S. federal legislation. These cuts adversely impact Medicare payment for all dialysis treatments and could affect adoption of home and more frequent hemodialysis.

Medicaid.    Medicaid programs are state-administered programs partially funded by the federal government. These programs are intended to provide coverage for certain categories of patients whose income and assets fall below state defined levels and who are otherwise uninsured. For those who are eligible, the programs serve as supplemental insurance programs for the Medicare co-insurance portion and provide certain coverage, such as self-administered outpatient prescription medications, that is not covered by Medicare. For ESRD treatment, state regulations generally follow Medicare reimbursement levels and coverage without any co-insurance amounts, which is pertinent mostly for the three-month waiting period for Medicare coverage. Certain states, however, require beneficiaries to pay a monthly share of the cost based upon levels of income or assets.

Private Insurers.    Some ESRD patients have private insurance that covers dialysis services. Healthcare providers receive reimbursement for ESRD treatments from the patient or private insurance during a waiting period of up to three months before the patient becomes eligible for Medicare. In addition, if the private payor is an employer group health plan, it is generally required to continue to make primary payments for dialysis

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services during the 30-month period following eligibility or entitlement to Medicare. In general, employers may not reduce coverage or otherwise discriminate against ESRD patients by taking into account the patient’s eligibility or entitlement to Medicare benefits. It is generally believed that private insurance pays significantly more for dialysis services than Medicare and these patients with private insurance are generally viewed as more profitable to dialysis service providers. In 2012, both United Healthcare and Aetna established formal policies covering home hemodialysis for its beneficiaries.

Critical Care Market

For Medicare patients, both acute kidney failure and fluid overload therapies provided in an in-patient hospital setting are reimbursed under a traditional Medicare severity diagnosis related group system. Under this system, reimbursement is determined based on a patient’s primary diagnosis and is intended to cover all of the hospital’s costs of treating the patient. The presence of acute kidney failure or fluid overload increases the severity of the primary diagnosis and, accordingly, could increase the amount reimbursed. Longer hospitalization stays and higher labor needs, which are typical for patients with acute kidney failure and fluid overload, must be managed for care of these patients to be cost-effective. We believe that there is a significant incentive for hospitals to find a more cost-efficient way to treat these patients in order to improve hospital economics for these therapies.

Reimbursement Outside of the U.S.

The use of our products outside the U.S. is similarly affected by reimbursement policies adopted by foreign regulatory agencies, government managed health care systems and private insurance. Reimbursement for the treatment of patients using medical devices in the EU Member States is governed by complex mechanisms established on a national level in each country. These mechanisms vary widely among the EU Member States. Moreover, these mechanisms evolve constantly, reflecting the efforts of these countries to reduce public spending on healthcare. As a result, obtaining reimbursement for the treatment of patients using medical devices has become more and more challenging. We cannot, therefore, guarantee that the treatment of patients with our products would be reimbursed in any EU Member State.

The rules on the coverage and reimbursement of medical devices outside the U.S. and EU vary widely from country to country and often from hospital to hospital. In addition, healthcare reform proposals and medical cost containment measures in many foreign countries could, among other things, limit the use of our products and treatments in those countries and further reduce reimbursement available for such use or eliminate coverage altogether. These reforms or cost containment measures, including the uncertainty in the medical community regarding their nature and effect, could have an adverse effect on our customers’ purchasing decisions regarding our products and treatments within these regions.

Our Employees

As of December 31, 2014, we had approximately 3,400 employees, including full-time, part-time and temporary employees. From time to time we also employ independent contractors to support our engineering, marketing, sales, clinical and administrative organizations. Most of our employees are involved in the manufacture of our products and are employed outside of the U.S., with the significant majority employed in Mexico.

Executive Officers

Our executive officers as of February 26, 2015 were as follows:

Jeffrey H. Burbank, 52, is our Chief Executive Officer and a member of our Board of Directors and has served in these positions since he founded the company in December 1998. Mr. Burbank has over 25 years of in-depth management experience with companies developing, marketing and manufacturing products for ESRD

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patients. He has led NxStage since its inception, guiding it through all of its developmental phases to the successful initiation and rapid growth of commercial activities, its initial public offering, and the acquisition of Medisystems Corporation. Prior to founding NxStage, Mr. Burbank co-founded Vasca, Inc., a company providing innovative implantable access devices, where he was the President and Chief Executive Officer, as well as Chairman of the Board. He gained significant renal industry experience during his nine years in the Renal Division at Gambro, Inc., a medical technology company, with his last position as Director of Marketing and Advanced Technologies. During his career he has been an inventor on over 50 U.S. patents for medical devices. Mr. Burbank received his BS in Industrial Engineering from Lehigh University.

Robert S. Brown, 56, is the President of NxStage Kidney Care and has served in this position since June 2013. Before that, he served as our Senior Vice President, Chief Financial Officer and Treasurer since 2006. Mr. Brown has more than 20 years of financial experience. Prior to joining NxStage, Mr. Brown held several leadership positions in the financial group of Boston Scientific Corporation, a medical device company, including Vice President, Corporate Analysis & Control, where he and his team were responsible for the company’s financial, compliance, and operational audits and reported directly to the audit committee of the board of directors. Mr. Brown also served as Vice President, International at Boston Scientific where he was responsible for the financial functions of the company’s $2.5 billion international division in over 40 countries. Previous experience also includes financial reporting and special projects at United Technologies, a high technology manufacturer, and public accounting and consulting at Deloitte & Touche, an auditing firm. Mr. Brown received his BBA from The University of Toledo and his MBA from The University of Michigan. He is also a Certified Public Accountant.

Winifred L. Swan, 50, is our Senior Vice President and General Counsel and has served in these positions since January 2005. Before that, she served as our Vice President and General Counsel since November 2000. Ms. Swan has over 20 years of legal expertise in medical devices. Prior to joining NxStage, Ms. Swan was Senior Corporate Counsel at Boston Scientific Corporation, a medical device company, where she focused on mergers and acquisitions and business development transactions. Before that, she was an associate at Goodwin Procter LLP, a law firm, specializing in corporate and securities law. Prior to law school, Ms. Swan served as a financial analyst in the Capital Markets Group of Merrill Lynch, a financial management and advisory company. Ms. Swan received a BA in Economics and Public Policy from Duke University and her JD from the University of Pennsylvania.

Matthew W. Towse, 52, is our Senior Vice President, Chief Financial Officer and Treasurer and has served in these positions since July 2013. He has also served as our Chief Accounting Officer since January 2015. Mr. Towse has over 25 years of experience in global financial management with both public and private companies across multiple industries. Prior to joining NxStage, he served as Vice President and Chief Financial Officer of Vette Corp., a venture-capital backed global design, engineering and manufacturing technology company from 2006 until its acquisition by a strategic buyer in April 2012. From 2003 to 2005, he served as Senior Vice President and Chief Financial Officer of Fairchild Semiconductor International, Inc. Previously, Mr. Towse served as Fairchild’s Vice President and Corporate Treasurer from 1997 to 2003, and held various financial positions with National Semiconductor from 1991 to 1997 before becoming part of the team that spunoff Fairchild from National. Earlier in his career, Mr. Towse was an audit manager with Ernst & Young LLP, an auditing firm, and most recently, he served as an Interim Chief Financial Officer with Tatum, LLC, an executive services firm. Mr. Towse is a Certified Public Accountant and received his BBA from the University of Notre Dame.

Joseph E. Turk, Jr., 47, is our President and has served in this position since November 2013. Before that, Mr. Turk served as our President of North American Operations from December 2010 to November 2013, Senior Vice President, Commercial Operations from January 2005 to December 2010 and Vice President, Sales and Marketing from May 2000 to January 2005. Mr. Turk brings a strong strategy and market development background to NxStage. Prior to joining NxStage, he served as Director of New Business Development at Boston Scientific Corporation, a medical device company. Before that, he was one of the leaders of the Midwest Health

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Care and Biotechnology Practice of McKinsey & Company, a management consulting firm, as a Senior Engagement Manager in the firm’s Chicago office. Mr. Turk received an AB in Economics from Wabash College and his MBA in Marketing and Finance from Northwestern University’s J.L. Kellogg School.

Where To Find More Information

Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934 are available free of charge through our website (www.nxstage.com) under the “Investor Relations” subsection of the “Our Company” section of the site as soon as reasonably practicable after we electronically file such material with, or furnish it to, the Securities and Exchange Commission, or SEC. In addition, we intend to disclose on our website any amendments to, or waivers from, our code of business conduct and ethics that are required to be disclosed pursuant to the rules of the SEC. We are not including the information contained on our website as part of, or incorporating it by reference into, this report.

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Item 1A. Risk Factors

In addition to the factors discussed in “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this report, the following are some of the important factors that could materially and adversely affect our business, financial condition, results of operations and common stock price and cause our actual results to differ materially from those projected in any forward-looking statements.

Risks Related to our Business

We expect to derive most of our future revenues from the System One and related products.

We expect to derive most of our future revenues from the sale or rental of the System One and the related products used with the System One, with the remainder of our revenues largely coming from the sale of a few key disposable products, including blood tubing sets and needles. To the extent that any of our primary products are not commercially successful or are withdrawn from the market for any reason, our revenues and business prospects will be adversely impacted.

The home dialysis market may be smaller than we expect and may be slow to develop.

We believe our largest product market opportunity is the home dialysis market. However, this market is presently very small and adoption of home hemodialysis therapies has been limited. Only 11% of U.S. chronic dialysis patients receive dialysis treatment at home, with most of such patients receiving peritoneal dialysis rather than home hemodialysis. Most dialysis centers presently do not have the infrastructure to support a significant home hemodialysis patient population. Our growth depends on a significant shift in patients’ and the medical community’s understanding and view of home hemodialysis, and will require a substantial increase in the number of patients who adopt home hemodialysis, physicians who are willing to prescribe home hemodialysis, and dialysis centers that are willing to support home hemodialysis. We operate a small number of dialysis centers focused on supporting home therapy with NxStage technology as part of our market development activities to increase home therapy access. We will need to continue to devote significant resources to expanding the market for our products, but these efforts ultimately may not be successful.

Because nearly all of our home hemodialysis patients are also receiving dialysis more frequently than the traditional thrice weekly treatment, market adoption of the System One for home hemodialysis is also dependent upon the penetration and market acceptance of more frequent hemodialysis. Given the increased provider costs associated with providing more frequent dialysis, market acceptance will be impacted, especially for U.S. Medicare patients, by whether dialysis centers obtain adequate reimbursement for additional dialysis treatments provided in excess of three times a week, which is discussed in the immediately following risk factor. New regulations particularly impacting home hemodialysis technologies may impede further market expansion of the System One for home hemodialysis. We saw the impact of such regulations in 2008, when the Centers for Medicare and Medicaid Services released new Conditions for Coverage that imposed water testing requirements on patients using our PureFlow SL product. These water testing requirements increased the burden of our therapy for patients and may have impaired market adoption, especially for our PureFlow SL product. To the extent additional regulations are introduced that are unique to the home environment, market adoption of the System One could be further impaired.

Current Medicare reimbursement rates, at three times per week, limit the price at which we can market our home hemodialysis products, and adverse changes to reimbursement would likely impede the adoption or continued sale of our home products.

Medicare provides broad and well-established reimbursement in the U.S. for treating end-stage renal disease patients with hemodialysis three times a week. Most patients using the System One in the home, however, treat themselves, with the help of a care partner, up to six times per week. Reimbursement for more frequent hemodialysis requires medical justification provided by the dialysis facility based on information from the

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patient’s physician. The total number of paid treatments may vary due to differing policies of Medicare contractors, as well as from varying center billing practices. Currently, only three of the Medicare contractor jurisdictions have formal local coverage determinations; the majority have not issued a local coverage determination and thus make coverage determinations on a case by case basis. One Medicare contractor without such a local coverage determination, Noridian Healthcare Solutions, recently issued a Medicare coverage article discussing considerations for hemodialysis frequency. Certain language in the coverage article is unclear or inconsistent with long-standing Medicare policy, including that reiterated in the 2015 Medicare payment rules, but it may suggest a limitation to coverage of more frequent hemodialysis, even with medical justification. In partnership with other provider, patient, and professional organizations, we have actively engaged Noridian on this question. It remains unclear how the article will be implemented. Some customers may not receive or pursue additional reimbursement in all cases, and providing the required medical justification for treatments beyond three times per week increases administrative burden. Although access to home and more frequent hemodialysis continues to grow, we believe that current Medicare reimbursement policies lead to adoption rates lower than rates commensurate with the percentage of patients experts believe can competently perform and medically benefit from this therapy. We believe that more predictable Medicare reimbursement for more frequent dialysis with less administrative burden, including further improving Medicare reimbursement for home hemodialysis training, would allow adoption of more frequent home hemodialysis at rates more consistent with what are deemed to be appropriate by the medical community. These beneficial changes, however, may never materialize. Conversely, any reduction in reimbursement rates or adverse changes in the reimbursement criteria for home or more frequent hemodialysis could materially reduce our revenues, earnings and cash flows.

In 2011, the Centers for Medicare and Medicaid Services implemented a new prospective payment system for dialysis treatment. Under the new prospective payment system, the Centers for Medicare and Medicaid Services makes a single bundled payment to the dialysis facility for each dialysis treatment that covers all renal dialysis services, inclusive of home dialysis and most drugs frequently administered to dialysis patients. This payment system replaced the former system which paid facilities a composite rate for a defined set of items and services, while paying separately for drugs, laboratory tests, and other services that were not included in the composite rate. With a vast majority of U.S. patients with end-stage renal disease covered by Medicare, the Medicare reimbursement rate is an important factor in a potential customer’s decision to use the System One or our other products and limits the prices we may charge for our products. It is also an important factor in the revenues received by our Kidney Care dialysis centers. A stated goal of the new prospective payment system was to encourage home dialysis. To date, it has not had a positive impact on the adoption of home or more frequent hemodialysis or the price of our products. However, the prospective payment system has had a significant positive impact on the adoption of peritoneal dialysis as evidenced by the significantly increased training rates for peritoneal dialysis. We believe this increased focus on peritoneal dialysis growth and peritoneal dialysis training has been to the detriment of home hemodialysis training rates, as home training resources, including home training nurses in particular, have been more devoted to peritoneal dialysis training, leaving less time for home hemodialysis training.

As part of the American Taxpayer Relief Act of 2012, Congress instructed the Centers for Medicare and Medicaid Services to recalculate the base payment rate under the prospective payment system for services furnished in 2014 and thereafter to account for changes in utilization of renal dialysis drugs since the prospective payment system was implemented. In response, the Centers for Medicare and Medicaid Services enacted a 12% reduction to the base payment rate to be implemented over a three- to four-year transition period, with overall payments for 2014 remaining unchanged. However, the Protecting Access to Medicare Act of 2014 replaced this phased-in reduction with reductions to the annual inflation adjustment to the base rate (known as the “market basket adjustment”) in 2015–2018. As a result, there is no reduction to the market basket adjustment in 2015, and the reduction is 1.25 percentage points in 2016 and 2017, and 1 percentage point in 2018. The effect of this change on the adoption of home and more frequent hemodialysis is not yet known.

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We have a history of net losses and a significant accumulated deficit, and we may be unable to become profitable or to sustain any profitability.

Since inception, we have incurred negative operating margins and losses every quarter. At December 31, 2014, we had an accumulated deficit of approximately $387.5 million. We expect our operating expenses to continue to increase as we grow and expand our business. While we have achieved positive gross profit for our products since the fourth quarter of 2007, we cannot provide assurance that our gross profit as a percentage of revenues will improve or, if it does improve, the rate at which it will improve. Achieving gross profit improvements will depend upon our ability to introduce additional process improvements and product design changes, further rationalize our manufacturing operations and supply chain, realize additional economies of scale, and continue to improve product reliability. We may not be successful at these and other cost reduction initiatives, and cannot provide assurance about achieving profitability, or the timing, extent or sustainability of such profitability.

Our customers in the System One and In-Center segments are highly consolidated and have concentrated buying power.

DaVita and Fresenius own and operate the two largest chains of dialysis centers in the United States. Collectively, these entities provide treatment to over two-thirds of U.S. dialysis patients, and this percentage may continue to grow with further market consolidation. These large dialysis providers have significant purchasing power and we may be required to grant them favorable pricing and other terms for our products that reduce our gross margins and have an adverse effect on our operating results.

The partial or complete loss of sales to DaVita or Fresenius would materially impair our financial results.

DaVita and Fresenius are our two largest customers, with sales to them representing approximately half of our total revenues during 2014. Our home market agreements with DaVita and Fresenius are intended to support the continued expansion of patient access to home hemodialysis with the System One, but like all our agreements with home market customers, these agreements are not requirements contracts and they contain no minimum purchase volumes. Our home market agreement with DaVita expires at the end of 2015 and our home market agreement with Fresenius expires at the end of 2016, and there can be no assurance that we will renew or extend these agreements on similar terms, if at all, before their expiration. We have no assurance that our sales to DaVita or Fresenius will continue to grow. Given the significance of DaVita and Fresenius as customers in the home market, any adverse change in either customer’s ordering or clinical practices, as might be the case in periodic contract negotiations or in response to the establishment of our NxStage Kidney Care dialysis centers, would have a significant adverse impact on our revenues.

We face additional risks from the acquisition or development of new lines of business, including in connection with establishing our NxStage Kidney Care dialysis centers.

In the course of evaluating growth opportunities, we may acquire or develop a new line of business or products. For example, we recently began establishing a small number of NxStage Kidney Care dialysis centers, which are dialysis centers focused on the provision of home therapy and flexible in-center options. There are substantial risks and uncertainties associated with any change in business lines or strategy, particularly in instances where our customers may perceive the new activity or business line to be in direct competition with their business, which could, in turn, lead them to stop or reduce their purchases of products from us. In addition to the external risks such new businesses or strategies may represent, we may face internal risks relating to developing knowledge of and experience in the new business and recruiting professionals, as well as business execution risks. New strategies and businesses may also require significant investment and involvement of our senior management, which will take away from the time they ordinarily spend on the remainder of our business.

If we make any strategic businesses acquisitions, we may encounter substantial integration risks that may prevent us from realizing the anticipated benefits of our acquisitions. These risks include:

• difficulty in transitioning and integrating the operations and personnel of the acquired businesses, including with respect to differing and complex accounting and financial reporting systems;

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• disruption of our ongoing business and distraction of management;

• difficulty in successfully implementing, upgrading and deploying in a timely and effective manner new operational information systems and upgrades of our finance, accounting and product distribution systems;

• difficulty in incorporating acquired technology and rights into our product and service offerings;

• unanticipated expenses and delays in completing acquired development projects and technology integration;

• difficulty in managing geographically remote units both in the United States and internationally;

• impairment of relationships with partners and customers;

• customers delaying purchases of our products pending resolution of product integration between our existing and our newly acquired products;

• entering markets or types of businesses in which we have limited experience;

• loss of key employees of the acquired company; and

• inaccurate assumptions of the acquired company’s product or service quality.

Failure to manage the risks associated with the development and implementation of new businesses or strategies could materially and adversely affect our business, results of operations and financial condition.

Our NxStage Kidney Care dialysis centers introduce significant new risks to our business.

In addition to implicating some of the same business and regulatory risks as are applicable to our medical products business (including in particular risks related to reimbursement), establishing our NxStage Kidney Care dialysis centers requires that we comply with complex regulatory requirements applicable to this new business. As health care providers and participants in federal health care programs, our NxStage Kidney Care dialysis centers are subject to extensive government regulations, including:

• Medicare and Medicaid payment rules, including coverage rules that limit the clinical circumstances under which payment will be made for more frequent dialysis treatments;

• anti-kickback and related laws prohibiting payments and other remuneration intended to influence the referral of health care business or selection of a provider;

• antitrust laws;

• prohibitions on submitting false claims for government reimbursement;

• laws regulating the use and disclosure of patient health information; and

• laws regulating the storage and administration of pharmaceuticals and medical devices.

Violations of such laws and regulations may be punishable by criminal and civil sanctions against us, including fines and civil monetary penalties and exclusion from participation in government programs, including Medicare and Medicaid, as well as against executives overseeing our business. In addition to penalties for violation of laws and regulations, we could be required to repay amounts we received from government payors, or pay additional damages and interest, if we are found to have submitted improper claims for reimbursement to the government. Whether or not we have complied with the law, an investigation into alleged unlawful conduct could increase our expenses, damage our reputation, divert management time and attention and adversely affect our business.

We compete against other dialysis equipment manufacturers with much greater financial resources and established products and customer relationships, which may make it difficult for us to penetrate the market and achieve significant sales of our products.

Fresenius, our second largest customer, markets its own home hemodialysis system. Fresenius may at any time reduce its promotion of our dialysis products to its dialysis patients in favor of its own dialysis products.

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Fresenius has also indicated that it is seeking clearance for its sorbent technology within the critical care setting, and has suggested that it would seek clearance for its Portable Artificial Kidney to market in the United States for in-center use. Baxter obtained CE marking for a new home hemodialysis system in the European Union in December 2013 and has discussed its plans for a near-term European launch. Baxter has also discussed plans to complete additional clinical studies and file for regulatory approval for a home nocturnal hemodialysis indication in the United States. Other small companies are also working to develop products for this market. We are unable to predict when, if ever, any of these products may attain regulatory clearance and appear in the market, or how successful they may be should they be introduced, but the introduction of additional viable products to the home market could adversely affect our sales and growth.

The System One in the critical care market competes against products from Gambro, a subsidiary of Baxter, Fresenius, B. Braun Medical, Inc. and others. Our product lines in the in-center market compete directly against products produced by Fresenius, Nipro Medical Corporation, B. Braun, Baxter together with its subsidiary Gambro, JMS Co. Ltd. and others. Our competitors in each of these markets sell one or more FDA-cleared medical devices for the treatment of acute or chronic kidney failure. Each of these competitors offers products that have been in use for longer than the System One and are more widely recognized by physicians, patients and providers. These competitors have significantly more financial and human resources, more established sales, service and customer support infrastructures and spend more on product development and marketing than we do. Many of our competitors also have established relationships with the providers of dialysis therapy, including Fresenius which owns and operates a chain of dialysis centers. The product lines of most of these companies are broader than ours, enabling them to offer a broader bundle of products and have established sales forces and distribution channels that may afford them a significant competitive advantage. Further consolidation within the highly competitive dialysis industry, demonstrated most recently by Baxter’s acquisition of Gambro, may exacerbate these risks.

The market for our products is competitive, subject to change and affected by new product introductions and other market activities of industry participants, including increased consolidation of ownership of centers by large dialysis chains. If we are successful, our competitors are likely to develop products that offer features and functionality similar to our products, including the System One. Improvements in existing competitive products or the introduction of new competitive products may make it more difficult for us to compete for sales, particularly if those competitive products demonstrate better reliability, convenience or effectiveness or are offered at lower prices.

Our ability to successfully market our products could also be adversely affected by pharmacological and technological advances in preventing the progression of end-stage renal disease or in the treatment of acute kidney failure or fluid overload. If we are unable to effectively respond to and compete against competitors, alternative treatments and pharmacological and technological advances, it will be difficult for us to expand the market for, and achieve significant sales of, our products.

Our continued growth is dependent on our development and successful commercialization of new and improved products.

Our future success will depend in part on our timely development and introduction of new and improved products that address changing market requirements. To the extent that we fail to introduce new and innovative products, including without limitation the next generation System One, or incremental product improvements, we may lose revenues or market share to our competitors, which may be difficult to regain. Our inability, for technological, regulatory, operational or other reasons, to successfully develop and introduce new or improved products could reduce our growth rate or otherwise damage our business. Our developments may not keep pace with the marketplace and our new or improved products may not adequately meet the requirements of the marketplace.

The success and growth of our business will depend upon our ability to achieve expanded market acceptance of the System One.

In the home market, we have to convince five distinct constituencies involved in the choice of dialysis therapy, namely operators of dialysis centers, nephrologists, dialysis nurses, patients and payors (private payors

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and Medicare), that the System One provides an effective alternative to other existing dialysis equipment. In the in-center market, we have to convince most of the same constituencies that our blood tubing sets and needles provide an effective alternative to other dialysis disposables. In the critical care market, we have to convince hospital purchasing groups, hospitals, nephrologists, dialysis nurses and critical care nurses that our system provides an effective alternative to other existing dialysis equipment. Each of these constituencies use different considerations in reaching their decision. Lack of acceptance by any of these constituencies will make it difficult for us to grow our business.

We may have difficulty gaining widespread or rapid acceptance of any of our products, including the System One, for a number of reasons including:

• our failure to demonstrate that our products are equivalent or superior to existing therapy options;

• competition from products sold by companies with longer operating histories and greater financial resources, more recognizable brand names and better established distribution networks and relationships with hospitals or dialysis centers;

• our failure to continue to improve product reliability and the ease of use of our products;

• limitations on the existing infrastructure in place to support home hemodialysis, including without limitation, home hemodialysis training nurses, and the willingness, costs associated with, and ability of dialysis centers to build that infrastructure;

• the ownership and operation of some dialysis providers by companies that also manufacture and sell competitive dialysis products;

• the introduction of competing products or treatments that may be more effective, easier to use or less expensive than ours;

• regulations that impose additional burden on patients, such as the Medicare conditions for coverage which impose additional water testing requirements in connection with the use of our PureFlow SL;

• the number of patients willing and able to perform therapy independently, outside of a traditional dialysis clinic, may be smaller than we estimate; and

• the availability of satisfactory reimbursement from healthcare payors.

If we are unable to convince additional hospitals and healthcare providers of the benefits of our products for the treatment of acute kidney failure and fluid overload, we will not be successful in increasing our market share in the critical care market.

We sell the System One in the critical care market for use in the treatment of kidney failure and fluid overload. Physicians currently treat most acute kidney failure patients using conventional hemodialysis systems or dialysis systems designed specifically for use in the intensive care unit. We will need to convince hospitals and healthcare providers that using the System One is as effective as using conventional or intensive care hemodialysis systems for treating acute kidney failure or fluid overload and that it provides advantages over conventional or intensive care systems because of its significantly smaller size, ease of operation and clinical flexibility. In addition, the impact of tightened credit markets on hospitals could impair the manner in which we sell products in the critical care market. Hospitals facing pressure to reduce capital spending may choose to delay capital equipment purchases or seek alternative financing options.

Our business and results of operations may be negatively impacted by general economic and financial market conditions and such conditions may increase other risks that affect our business.

Global macro-economic conditions and the world’s financial markets remain susceptible to significant stresses, resulting in reductions in available credit, foreign currency fluctuations and volatility in the valuations of securities generally. In general, we believe demand for our products in the home and in-center markets will not

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be substantially affected by overall economic conditions as regular dialysis is a life-sustaining, non-elective therapy. However, hospitals or clinics facing pressure to reduce capital spending may choose to rent equipment rather than purchase it outright, or to enter into other less-capital intensive purchase structures with us, which may, in turn, have a negative impact on our cash flows. Hospitals or clinics may address budget constraints by reducing staff, resulting in fewer personnel available to train new patients for home hemodialysis. Uncertainty in the general economic environment and governmental spending on public health programs may also lead to a reduction in hospital days (particularly those due to elective procedures) and delays in capital purchases, both of which could negatively impact our critical care business. Our ability to sell products internationally is particularly vulnerable to adverse impacts from global macro economic conditions. Government funded hospitals in various international markets may seek to defer capital purchases or tenders or reduce staff in response to economic pressures. Distributors with reduced access to capital may be less willing to purchase our equipment outright, impairing our ability to sell our products. Furthermore, unfavorable changes in foreign exchange rates versus the U.S. dollar would increase our product costs which would negatively impact our gross profit and gross profit as a percentage of revenues.

Healthcare reform legislation could adversely affect our revenue and financial condition.

In recent years, there have been numerous initiatives on the federal and state levels, and in foreign countries, for comprehensive reforms affecting the availability of and reimbursement for healthcare services. These initiatives have ranged from fundamental changes to federal and state healthcare reimbursement programs, such as providing comprehensive healthcare coverage to the public under governmental funded programs, to minor modifications to existing programs.

In 2010, comprehensive health care reform legislation was passed that, among other things, imposes a 2.3% excise tax on domestic sales of certain medical devices. Our profitability has been negatively impacted due to the medical device excise tax assessed on nearly all of our products sold in the United States since the beginning of 2013. Subsequent legislation required an adjustment to the Medicare payment rates starting in 2016. These changes could affect the adoption of home and more frequent hemodialysis in the future, particularly if NxStage customers are distracted in efforts to address any revenue shortfalls, or choose to redirect home training resources toward other center activities. Additional healthcare reforms in the United States may have a material adverse effect on our financial condition and results of operations.

The governments of foreign countries are actively pursuing similar actions intended to reduce costs related to provision of healthcare. The results of these actions may also have a material adverse effect on our financial condition and results of operations.

As our business continues to grow, we may have difficulty managing our growth and expanding our operations successfully.

As our business continues to grow, we will need to expand our manufacturing, sales and marketing and on-going development capabilities or contract with other organizations to provide these capabilities for us. As our operations expand, we expect that we will need to manage additional relationships with various partners, suppliers, manufacturers and other organizations. Our ability to manage our operations and growth requires us to continue to improve our information technology infrastructure, operational, financial and management controls and reporting systems and procedures. Such growth could place a strain on our administrative and operational infrastructure. We may not be able to make improvements to our information management and control systems in an efficient or timely manner and may discover deficiencies in existing systems and controls. Also, if demand for our products continues to grow we may not be able to increase our manufacturing capacity fast enough to meet customer demand.

If we are unable to maintain strong product reliability for our products, we may be unable to grow our business and achieve profitability.

Product reliability issues associated with any of our product lines could lead to decreases in customer satisfaction and our ability to grow or maintain our revenues and could negatively impact our reputation. Further,

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any unfavorable changes in product reliability would result in increased service and distribution costs which negatively impacts our gross profit and operating profit and increases our working capital requirements. We continue to work to maintain strong product reliability for all products. If we are unable to maintain strong product reliability for our existing products, our ability to achieve our growth objectives as well as profitability could be significantly impaired.

We also need to establish strong product reliability for all new products we offer. With new products, we are more exposed to risks relating to product quality and reliability until the manufacturing processes for these new products mature. We also choose from time to time to transition the manufacturing and supply of products and components to different suppliers or locations. As we make these changes, we are more exposed to risks relating to product quality and reliability until the manufacturing processes mature. Like all transitions of this nature, they could also lead us to incur additional costs in the near-term, which would negatively impact our gross profits in the near-term.

We have a significant amount of System One field equipment, and our inability to effectively manage this asset could negatively impact our working capital requirements and future profitability.

Because our home market relies upon an equipment service swap model and, for some of our customers, an equipment rental model, our ability to manage System One equipment is important to minimizing our working capital requirements. Both approaches require that we maintain a significant level of field equipment of the System One and PureFlow SL hardware. While a majority of our home market customers have committed to purchase, rather than rent, the significant majority of their future System One equipment requirements, there can be no assurance that we will be able to continue to expand or sustain this level of equipment placements that are purchased rather than rented. Any excess rental or service swap equipment would increase our ongoing cash requirements to fund working capital. In addition, our gross margins may be negatively impacted if we have excess equipment deployed and unused in the field. If we are unable to successfully track, service and redeploy equipment, we could incur increased costs, realize increased cash requirements and have material write-offs of equipment. This would negatively impact our working capital requirements and future profitability.

We may be subject to litigation claims from time to time.

From time to time, we are threatened with individual actions involving our business, including without limitation products liability, employment, intellectual property, commercial and tort claims. The manufacture and marketing of medical devices, in particular, has an attendant risk of product liability claims. If any of our employees or products is found to have caused or contributed to injuries or deaths, we could be held liable for substantial damages. Any claims made against us could adversely affect our reputation, which could damage our position in the market. Claims can also be time consuming, distracting, and expensive to defend and could result in a diversion of management and financial resources away from our primary business, in which case our business may suffer.

While we maintain insurance at levels deemed adequate by management, future claims could exceed our insurance coverage.

We maintain insurance for property and general liability, directors’ and officers’ liability, product liability, malpractice related to NxStage Kidney Care dialysis centers, workers compensation, and other coverage in amounts and on terms deemed to be adequate by management based on our expectations for future claims. Future claims, however, may be brought against us that result in court judgments or settlements that exceed the limits of our insurance coverage. In addition, our insurance policies have various exclusions, and we may be subject to a claim for which we have no coverage. As a result, we may have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by any insurance, which may have a material adverse effect on our financial condition and results of operations.

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We face risks associated with having international operations, and if we are unable to manage these risks effectively, our business could suffer.

We operate manufacturing facilities in Germany, Italy and Mexico. We also purchase components, products and supplies from foreign vendors. We are subject to a number of risks and challenges that specifically relate to these international operations, and we may not be successful if we are unable to meet and overcome these challenges. Significant risks relate to foreign currency, in particular the euro and peso. To mitigate our foreign currency exposure we engage in hedging transactions on peso denominated expenses. To the extent we fail to control our exchange rate risk, our gross profit as a percentage of revenues and profitability could suffer and our ability to maintain mutually beneficial and profitable relationships with foreign vendors could be impaired. In addition to these risks, through our international operations we are exposed to costs and challenges associated with sourcing and shipping goods internationally and importing and exporting goods, difficulty managing operations in multiple locations, local regulations that may restrict or impair our ability to conduct our operations and increase compliance costs, health issues, such as pandemic disease risk, and natural disasters, such as flooding, hurricanes and earthquakes, which could disrupt our manufacturing and logistical and import activities. Risks associated with our international operations may increase where we sell our products and services directly rather than through distributors, such as in the United Kingdom. Furthermore, in certain locations, such as Mexico, we are also exposed to risks associated with local instability, including threats of violence, which could lead to disruptions in supply at our manufacturing facilities or key vendors.

Our In-Center segment relies heavily upon third-party distributors.

Substantially all of our products for the in-center market are sold through distributors. Relying on third-party distributors exposes us to many risks, including competitive pressure, compliance risks, credit risk and concentration. Distributors may sell products that compete with our products, and we may be unsuccessful in motivating our distributors to focus their efforts on selling our products. Any failure on the part of our distributors to comply with applicable laws in the sale and marketing of our products or to fulfill any responsibilities they may have to protect the intellectual property rights underlying our products could have an adverse effect on our revenues and involve us in legal proceedings. Distributors may face financial difficulties, including bankruptcy, which could harm our collection of accounts receivable and financial results. In addition, Gambro (a subsidiary of Baxter) and Henry Schein are our most significant distributors for the in-center market, and the loss of Gambro or Henry Schein as our distributors for any reason could materially adversely affect our business, at least in the near term. Our distribution agreement with Henry Schein expires on April 25, 2015, and we are negotiating the terms of a new distribution agreement with Henry Schein. If we are unsuccessful in renewing our distribution relationship with Henry Schein on mutually agreeable terms, transitioning this business to another distributor would adversely affect our business, at least in the near-term.

Unless we can demonstrate sufficient product differentiation in our In-Center segment products, we will continue to be susceptible to further pressures to reduce product pricing and more vulnerable to the loss of our blood tubing set or needle business to competitors in the dialysis industry.

Our blood tubing set and needle businesses have historically been commodities businesses. Our products continue to compete favorably in the dialysis blood tubing set and needle business, but are increasingly subject to pricing pressures, especially given recent market consolidation in the U.S. dialysis services industry, with Fresenius and DaVita collectively controlling over two-thirds of the U.S. dialysis services business. Unless we can successfully demonstrate to customers the differentiating features of our Streamline blood tubing set, MasterGuard needle, ButtonHole needle or products that we introduce in the future, we may continue to be susceptible to pressures to reduce our product pricing and more vulnerable to the loss of our blood tubing set and needle business to competitors in the dialysis industry.

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The success of our business depends on the services of each of our senior executives as well as certain key engineering, scientific, manufacturing, clinical and marketing personnel, the loss of whom could negatively affect our business.

Our success depends upon the skills, experience and efforts of our senior executives and other key personnel, including our research and development and manufacturing executives and managers. Much of our expertise is concentrated in relatively few employees, the loss of whom for any reason could negatively affect our business. Competition for our highly skilled employees is intense and we cannot prevent the future resignation of any employee. We maintain key person insurance for only our Chief Executive Officer.

If kidney transplantation becomes a viable treatment option for more patients with end-stage renal disease, or if medical or other solutions for renal replacement become viable, the market for our products may be limited.

While kidney transplantation is the treatment of choice for most patients with end-stage renal disease, it is not currently a viable treatment for most patients due to the limited number of donor kidneys, the high incidence of kidney transplant rejection and the higher surgical risk associated with older patients. The development of new medications designed to reduce the incidence of kidney transplant rejection, progress in using kidneys harvested from genetically engineered animals as a source of transplants or any other advances in kidney transplantation could limit the market for our products and services. The development of viable medical, pharmaceutical, or other solutions for renal replacement or prolonging kidney life may also limit the market for our products and services.

Risks Related to the Regulatory Environment

We cannot market or commercially distribute our products without obtaining and maintaining necessary regulatory clearances or approvals.

Our products are medical devices subject to extensive regulation in the United States. To market a medical device in the United States, approval or clearance by the FDA is required, either through the pre-market approval process or the 510(k) clearance process. We have obtained the FDA clearance necessary to sell our current products under the 510(k) clearance process. Medical devices may only be promoted and sold for the indications for which they are approved or cleared. In addition, even if the FDA has approved or cleared a product, it can take action affecting such product approvals or clearances if serious safety or other problems develop. We may be required to obtain 510(k) clearances or pre-market approvals for additional products, product modifications, or for new indications of our products. Regulatory pathways for such clearances may be difficult to define and could change. Delays in obtaining clearances or approvals could adversely affect our ability to introduce new products or modifications to our existing products in a timely manner, which would delay or prevent commercial sales of our products.

The FDA’s policies may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our future products. Although the 510(k) regulation has not been formally changed, the FDA has announced that it is intending to implement modifications to the 510(k) process. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained, which would adversely affect our business, prospects and the ability to sell and promote our products.

Our products are also subject to extensive regulation in foreign markets in which we are currently present or which we may wish to enter. The regulatory approval process outside the United States exposes us to many of the same risks associated with obtaining FDA clearance. Accordingly, we may be unable to obtain foreign regulatory approvals on a timely basis, if at all, which would limit our market expansion goals, and any existing foreign regulatory approvals may be curtailed, suspended or withdrawn, which would adversely affect our business. In addition, the regulatory approval procedure in foreign markets varies from country to country and requires that we comply with numerous regulatory requirements that differ from the FDA clearance process and are not

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superseded by obtaining clearance or approval from the FDA or another country’s regulatory authority. As these regulatory requirements become increasingly more stringent, it may become more difficult and costly for us to expand into new markets. In certain foreign markets, some of our products are classified as drugs rather than medical devices, which require us to demonstrate compliance with separate regulations applicable to drug manufacturers and distributors. These complex regulations may impose additional approval, manufacturing, surveillance and reporting requirements. Compliance with these additional requirements may increase our costs of doing business in new foreign markets and delay our entry into such markets.

New regulations affecting our business are periodically adopted in the United States and in other countries. These regulations may require us to change our existing product technologies, operating procedures or marketing practices in order to continue selling our products. This may expose us to increased costs, as well as risks that we may be unable to satisfy the new regulatory requirements. For example, extensive revisions to current EU medical device legislation, which is currently being discussed by the Council of the European Union, will impose significant additional obligations. If we are unable to comply with the new obligations imposed by the regulation, we may need to suspend, curtail or otherwise modify our selling and marketing efforts in the European Union. Any additional regulatory developments in the European Union or elsewhere may adversely affect our ability to market our existing products or introduce new products in a timely manner, which would have a negative impact on our business.

Modifications to our marketed devices may require new regulatory clearances or pre-market approvals, or may require us to cease marketing or recall the modified devices until clearances or approvals are obtained.

In the United States, modifications to a 510(k) cleared device that could significantly affect its safety or effectiveness, or would constitute a major change in its intended use, require the submission of another 510(k) pre-market notification to address the change. Although in the first instance we may determine that a change does not rise to a level of significance that would require us to make a pre-market notification submission, the FDA may disagree and require such a submission. If the FDA requires us to submit a 510(k) for any modification to a previously cleared device, we may be required to cease marketing the device, recall it, and not resume marketing until we obtain clearance from the FDA for the modified version of the device, and may be subject to fines or other sanctions for failing to obtain such clearance in advance. In the future, we intend to introduce new products and enhancements and improvements to existing products, which may not be cleared by the FDA in a timely manner, if at all. In addition, the FDA may characterize any new products or significantly modified marketed products in a class that requires submission of a more costly and lengthy pre-market approval application before commercial distribution would be permissible. Compared to 510(k) submissions, pre-market approval applications require substantially more data and their review by the FDA typically takes significantly longer. Also, products subject to pre-market approval applications require approval supplements for any change that affects safety and effectiveness before the modified device may be marketed. Delays in our receipt of regulatory clearance or approval will cause delays in our ability to sell our products, which will have a negative effect on the growth of our revenues.

Outside the United States, modifications to approved devices expose us to many of the same risks associated with modifications to 510(k) cleared devices. For example, in the European Union any substantial changes to a CE marked device may require a new conformity assessment and a new CE Certificate of Conformity from our notified body before the proposed change is implemented. There is limited guidance, however, on whether a change to a device should be considered substantial. Therefore, there is a risk that the competent authorities in the European Union or our notified body disagree with our assessment of the changes introduced to our products, and may come to a different conclusion than the FDA concerning such changes. Delays in conduct of any regulatory assessments in the European Union or elsewhere will cause delays in our ability to sell our products in those markets and will have a negative effect on our revenue growth.

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Even if we obtain the necessary regulatory clearances or approvals, if we or our suppliers fail to comply with ongoing regulatory requirements our products could be subject to restrictions or withdrawal from the market.

Numerous regulatory requirements apply to our products following clearance or approval in the United States, European Union, and other markets, including regulations governing:

• registration of medical devices;

• pricing and reimbursement of medical devices;

• establishment of post-marketing surveillance;

• field safety corrective actions, including product recalls and withdrawals;

• filing reports of device corrections and removals;

• marketing and promotion of medical devices; and

• interactions with physicians.

In addition, we are subject to the Medical Device Reporting regulations that require us to report to the FDA if our products may have caused or contributed to patient death or serious injury, or if our device malfunctions and a recurrence of the malfunction would likely result in death or serious injury. Similar obligations are imposed in foreign countries.

Our failure to comply with these or other applicable regulatory requirements may result in enforcement measures being taken by regulatory authorities, which may include:

• untitled letters, warning letters, fines, injunctions and civil penalties;

• detention of medical devices believed to be adulterated or misbranded;

• customer notification, or orders for repair, replacement or refund;

• voluntary or mandatory recall, withdrawal or seizure of our products;

• operating restrictions, partial suspension or total shutdown of production;

• refusal to review or delay in issuing pre-market notification or pre-market approval submissions;

• rescission of a regulatory clearance or approval that has already been granted;

• refusal to issue export documentation or approval for our products;

• suspension, withdrawal or variations of CE Certificates of Conformity or delay in obtaining new CE Certificates of Conformity;

• refusal of entry for imported products, materials and components; and

• criminal prosecution.

Such enforcement measures would require unanticipated expenditures to address or defend such actions and would have an adverse effect on the marketing of our products and, consequently, on our business and financial position.

Any market withdrawals or recalls of our products could expose us to product liability claims and harm our reputation and financial results.

Medical devices can experience performance problems in the field that require review and possible corrective action. The occurrence of component failures, manufacturing errors, design defects or labeling inadequacies affecting a medical device could lead to a government-mandated or voluntary recall by the device

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manufacturer, in particular when such deficiencies may endanger health. From time to time we have chosen to voluntarily recall certain products that we believed were mislabeled or otherwise defective. Although we do not believe that any of our recent recalls have had any long-term negative effect on our business, future recalls may materially divert management attention and financial resources, expose us to product liability or other claims, and harm our reputation with customers.

If we or our contract manufacturers fail to comply with the FDA’s Quality System Regulations and other quality system requirements, our manufacturing operations could be interrupted, and our product sales and operating results could suffer.

Our finished goods manufacturing processes, and those of some of our contract manufacturers, must comply with the FDA’s Quality System Regulations which cover the procedures and documentation of the design, testing, production, control, quality assurance, labeling, packaging, sterilization, storage and shipping of our devices. Foreign regulatory authorities impose similar obligations. The FDA enforces these regulations through periodic unannounced inspections of manufacturing facilities. We and our contract manufacturers have been subject to such inspections on multiple occasions and we anticipate additional inspections in the future. While our previous inspections have resulted in no significant observations, we cannot provide assurance that we can maintain a comparable level of regulatory compliance in the future at our facilities, or that future inspections would have the same result.

If one of our manufacturing facilities or those of any of our contract manufacturers fails to take satisfactory corrective action in response to an adverse quality system inspection, the FDA, the notified body, or the competent authorities in the European Economic Area could take enforcement action, including:

• issuing a public warning letter;

• shutting down part or all of our manufacturing operations;

• suspending or withdrawing our existing CE Certificates of Conformity;

• embargoing the import of certain components;

• ordering the recall or detention of our products;

• refusing to approve new marketing applications or to issue new CE Certificates of Conformity;

• instituting legal proceedings to detain, seize or enjoin the manufacture or distribution of our products; and

• imposing administrative, civil or criminal penalties or other sanctions.

Any of these actions could harm our business, reputation and operating results.

We have obligations to protect the privacy and security of patient health information. Failure or perceived failure to comply with applicable federal and state requirements could subject us to criminal or civil penalties, and contractual liability.

In the course of performing our business we obtain, from time to time, confidential patient health information. For example, we learn patient names and addresses when we ship System One supplies to home hemodialysis patients. We may learn patient names and be exposed to confidential patient health information when we provide training on our products to our customers’ staff. Our home hemodialysis patients may also call our customer service representatives directly and, during the call, disclose confidential patient health information. We also receive and maintain confidential patient health information in connection with the operation of our NxStage Kidney Care dialysis centers. U.S. federal and state laws protect the confidentiality of certain patient health information, in particular individually identifiable information, and restrict the use and disclosure of that information. At the federal level, the Health Insurance Portability and Accountability Act of 1996 and its implementing regulations, as amended under the Health Information Technology for Economic and Clinical

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Health Act, or HIPAA, governs the use and disclosure of confidential patient health information known as protected health information. HIPAA and the rules promulgated thereunder require certain entities to comply with established standards, including standards regarding the privacy and security of protected health information known as the HIPAA Privacy and Security Rules, and to provide notification following a data breach involving protected health information. We are subject to HIPAA with regard to certain aspects of our business. In addition, many other state and federal laws regulate the use and disclosure of health information, including state medical privacy laws, breach notification laws and federal and state consumer protection laws. In many cases, these laws are not necessarily preempted by HIPAA, particularly if they afford greater protection to the individual than does HIPAA.

Complying with these federal and state privacy and security requirements impose compliance related costs, subjects us to potential regulatory audits, and may restrict our business operations. These various laws may be subject to varying interpretations by courts and government agencies creating potentially complex compliance issues for our business. If we were to violate any of our legal obligations to safeguard any confidential patient health information or protected health information against improper use and disclosure, we could lose customers and be exposed to liability, including potential civil and criminal penalties under HIPAA and contractual liabilities, and our reputation and business could be harmed. Concerns or allegations about our practices with regard to the privacy or security of personal health information or other privacy-related matters, even if unfounded, could damage our reputation and harm our business.

We are also subject to laws and regulations in foreign countries covering data privacy and other protection of health and employee information that may be more onerous than corresponding U.S. laws. These regulations may require that we obtain individual consent before we collect or process any personal data, restrict our use or transfer of personal data, impose technical and organizational measures to ensure the security of personal data, and require that we notify regulatory agencies, individuals or the public about any data security breaches. As we expand our international operations, we may be required to expend significant time and resources to put in place additional mechanisms to ensure compliance with multiple data privacy laws. Failure to comply with these laws may result in significant fines and other administrative penalties and harm our business.

We may be subject to fines, penalties or injunctions if we are determined to be promoting the use of our products in a manner not consistent with our products’ cleared indications for use or with other state or federal laws governing the promotion of our products.

Our promotional materials and other product labeling must comply with FDA rules and other applicable laws and regulations. If the FDA or other federal, state or foreign enforcement authorities determine that our promotional materials or other product labeling constitute promotion of an unapproved or uncleared use, it could request that we modify our materials or subject us to regulatory or enforcement actions, including the issuance of an untitled letter, a warning letter, injunction, seizure, civil fine and criminal penalties. Promotional activities related to our NxStage Kidney Care dialysis centers also may be scrutinized. Other federal, state and foreign regulatory agencies, including the U.S. Federal Trade Commission, have issued guidelines and regulations that govern how we promote our products and services, including how we use endorsements and testimonials. If our promotional materials or activities are inconsistent with any of these guidelines or regulations, we could be subject to enforcement actions, which could result in significant fines, costs and penalties. Our reputation could also be damaged and the adoption of our products could be impaired.

Medical devices in the European Union may be promoted only for the intended purpose for which the devices have been CE marked. Failure to comply with this requirement could lead to the imposition of penalties by the competent authorities of the EU Member States. The penalties could include warnings, orders to discontinue the promotion of the medical device, seizure of the promotional materials and fines. Our promotional materials must also comply with various laws and codes of conduct developed by medical device industry bodies in the European Union governing promotional claims, comparative advertising, advertising of medical devices reimbursed by the national health insurance systems and advertising to the general public. If our promotional materials do not comply with these laws and industry codes we could be subject to penalties that could include significant fines. Our reputation could also be damaged and the adoption of our products could be impaired.

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We are subject to federal and state laws prohibiting “kickbacks” and false and fraudulent claims which, if violated, could subject us to substantial penalties.

The federal healthcare program Anti-Kickback Statute, and similar state laws, prohibit payments and other forms of remuneration that are intended to induce health care professionals or others either to refer patients or to purchase, lease, order or arrange for or recommend the purchase, lease or order of healthcare products or services. Other laws prohibit remuneration intended to induce patients to select a particular provider of services, including for dialysis. A number of states have enacted laws that require pharmaceutical and medical device companies to monitor and report payments, gifts and other remuneration made to physicians and other health care professionals and health care organizations. Some state statutes, most notably laws in Massachusetts and Vermont, impose outright bans on certain manufacturer gifts to physicians. Some of these laws, referred to as “aggregate spend” or “gift” laws, carry substantial fines if they are violated. In addition, under the federal Physician Payments Sunshine Act we must collect and report certain data on payments and other transfers of value to physicians and teaching hospitals, which became publicly available in 2014. It is widely anticipated that public reporting under the Sunshine Act will result in increased scrutiny of the financial relationships between industry, physicians and teaching hospitals.

These anti-kickback, public reporting and aggregate spend laws affect our sales, marketing and other promotional activities by limiting the kinds of financial arrangements, including sales programs, we may have with hospitals, physicians or other potential purchasers or users, including patients, of medical devices and services. They also impose additional administrative and compliance burdens on us. In particular, these laws influence, among other things, how we structure our sales and rental offerings, including discount practices, customer support, education and training programs and physician consulting and other service arrangements. For our NxStage Kidney Care dialysis centers, they also affect our arrangements with any joint venture partners in a position to refer patients, our medical directors and our patient billing and collection practices. Although we seek to structure such arrangements in compliance with all applicable requirements, these laws are broadly written and it is often difficult to determine precisely how these laws will be applied in specific circumstances. If we were to offer or pay inappropriate inducements to purchase, order or use our products or services, or to refer patients to our NxStage Kidney Care dialysis centers, we could be subject to a claim under the federal healthcare program Anti-Kickback Statute, the federal patient inducement prohibition or similar state laws. If we fail to comply with particular reporting requirements, we could be subject to penalties under applicable federal or state laws.

Other federal and state laws generally prohibit individuals or entities from knowingly presenting, or causing to be presented, claims for payments to Medicare, Medicaid or other third-party payors that are false or fraudulent, or for items or services that were not provided as claimed. Medical device manufacturers can be held liable under these laws if they are deemed to “cause” the submission of false or fraudulent claims by providing inaccurate billing or coding information to customers, by providing improper financial inducements, or through certain other activities. In providing billing and coding information to customers, we make every effort to ensure that the billing and coding information furnished is accurate and that treating physicians understand that they are responsible for all prescribing decisions, including the decision as to whether to order dialysis services more frequently than three times per week. In addition, our NxStage Kidney Care dialysis centers are directly subject to these laws with respect to the reimbursement claims they file with government payors. Potential false or fraudulent claim risk can arise from promoting and billing for services the government deems excessive or not medically necessary, as well as from other billing improprieties and from failure to timely return any identified overpayments. We are making every effort, including adhering strictly to guidelines in any local coverage determinations issued by Medicare contractors with jurisdiction over claims from any of our NxStage Kidney Care dialysis centers, to ensure that billing by our NxStage Kidney Care dialysis centers is proper and that physicians who order NxStage Kidney Care dialysis services fully document medical need for patients for whom more frequent than thrice weekly therapy is ordered. Nevertheless, we cannot provide assurance that the government will regard any billing errors that may be made as inadvertent or that the government will not examine our role in providing information to our customers, physicians and patients concerning the benefits and potential coverage of more frequent therapy. Likewise, our financial relationships with customers, physicians,

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patients or others in a position to influence the purchase or use of our products may be subject to government scrutiny or be alleged or found to violate applicable fraud and abuse laws. False claims laws prescribe civil, criminal and administrative penalties for noncompliance, which can be substantial, and given the possibility of exclusion from participation in government health care programs, potentially crippling to the line of business involved. Moreover, an unsuccessful challenge or investigation into our practices could cause adverse publicity, and be costly to respond to, and thus could harm our business and results of operations.

Increasingly, foreign countries are adopting laws similar in application and consequence to the anti-kickback, false claims and Sunshine Act laws in the United States. In the European Union, the provision of benefits or advantages to physicians to induce or encourage the prescription, recommendation, endorsement, purchase, supply, order or use of medical devices is prohibited. The provision of benefits or advantages to physicians is also governed by the national anti-bribery laws of the EU Member States. One such example is the UK Bribery Act. Increasingly, national laws or industry codes are imposing obligations of public disclosure of payments made to physicians in certain EU Member States. Moreover, agreements with physicians must often be the subject of prior notification and approval by the physician’s employer or competent professional organization or the competent authorities of the individual EU Member States. If we fail to comply with these laws we may face civil or criminal penalties. The negative consequences of any failure to comply with these laws may also harm our ability to operate in foreign countries and have a negative effect on our reputation that discourages third parties from doing business with us.

Foreign governments tend to impose strict price controls, which may adversely affect our future profitability.

We have begun to market the System One and certain of our other products internationally. In some foreign countries, particularly in the European Union, the pricing of medical devices is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after a device has been CE marked. To obtain reimbursement or pricing approval in some countries, we may be required to supply data that compares the cost-effectiveness of our products to other available therapies. If reimbursement of our products is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, it may not be profitable to sell our products outside of the United States, which would negatively affect the long-term growth of our business. Furthermore, reimbursement provided for our products in other jurisdictions could change, positively or negatively. In the event reimbursements were to be negatively changed, such as in the United Kingdom where we sell our products directly, our ability to sell our products could be impaired.

If we violate import and export laws, or if laws governing our exemption from certain duties change, we could be subject to significant fines, liabilities or other adverse consequences.

We import into the United States disposable medical supplies from our manufacturing facilities and vendors located outside the United States. We have manufacturing facilities in Mexico, Germany and Italy and export various components and assemblies related to those operations. To a lesser but increasing degree, we also export finished goods from the United States to foreign countries. The import and export of these items are subject to extensive and complex laws and regulations. To the extent we fail to comply with these laws or regulations, or fail to interpret our obligations accurately, we may be subject to significant fines, liabilities, import holds and a disruption in our ability to deliver product, which could harm our business and operating results to suffer. To the extent there are modifications to the Generalized System of Preferences or cancellation of the Nairobi Protocol tariff classifications that apply to our products such that our products would be subject to duties, our profitability would also be negatively impacted.

Failure to comply with the U.S. Foreign Corrupt Practices Act, UK Anti-Bribery Act or similar anti-bribery laws in other countries could subject us to penalties and other adverse consequences.

We are subject to the U.S. Foreign Corrupt Practices Act which generally prohibits U.S. companies from engaging in bribery or other prohibited payments to foreign officials for the purpose of obtaining or retaining

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business and requires companies to maintain accurate books and records and internal controls, including at foreign controlled subsidiaries. Through our international activities, we are also subject to the UK Anti-Bribery Act and other similar anti-bribery laws in other countries. While we have policies and procedures in place designed to promote compliance with such laws, our employees or other agents may nonetheless engage in prohibited conduct under these laws for which we might be held responsible. If our employees or other agents are found to have engaged in such practices, we could suffer severe penalties and other consequences that may have a material adverse effect on our business, financial condition and results of operations.

If we violate environmental and occupational safety laws regulating the use of hazardous materials and medical waste, we could be subject to significant fines, liabilities or other adverse consequences.

Our research and development programs as well as our manufacturing operations involve the controlled use of hazardous materials, and our NxStage Kidney Care dialysis centers produce medical waste in connection with providing dialysis services. Accordingly, we are subject to federal, state and local laws, as well as the laws of foreign countries, governing the use, handling and disposal of these materials. In the event of an accident or failure to comply with environmental or occupational safety laws, we could be held liable for resulting damages, and any such liability could exceed our insurance coverage.

Our business may be affected by U.S. government contracting risks.

We have agreements with Veterans Health Administration facilities and are one of the key subcontractors on a government contract to develop a portable medical device to treat sepsis. As a result, we must comply with and are affected by laws and regulations relating to the award, administration and performance of U.S. government contracts which, among other things, impose additional costs on our business. If we violate any of these laws or regulations, we may be liable for fines, penalties and any additional costs the government incurs in procuring replacement services, and we may be excluded from future U.S. government contracting.

Risks Related to Operations

We obtain some of our raw materials and production services from a single source or a limited group of suppliers, the loss of which may cause production delays and prevent us from delivering our products on a timely basis.

We depend upon a number of single-source suppliers for certain of our raw materials, components and finished goods, including the fiber used in our System One filters, our needles, premixed dialysate and sterile bags, as well as sterilization services. Some of our most critical single-source supply relationships are with Membrana and Laboratorios PiSA.

Membrana is our only supplier of the fiber used in our filters for System One products under an agreement that expires in December 2023, and contractually we cannot obtain an alternative source of fiber for our System One products. While our relationship with Asahi could afford us back-up supply in the event of supply disruptions at Membrana, we do not have the regulatory approvals necessary to use Asahi fiber in our System One cartridge in the United States and the performance of Asahi fiber in our System One has not yet been validated.

Laboratorios PiSA is our only supplier of premixed dialysate. Our supply agreement with Laboratorios PiSA extends through December 2019. We have committed to purchase from Laboratorios PiSA a minimum quantity of premixed dialysate over the term of the agreement. While we can purchase premixed dialysate from other qualified suppliers, any significant disruption in Laboratorios PiSA’s ability to supply premixed dialysate to us would impair our business, at least in the near term.

Our dependence upon these and other single-source suppliers of raw materials, components, finished goods and sterilization services exposes us to several risks, including disruptions in supply, price increases, late deliveries, and an inability to meet customer demand. This could lead to customer dissatisfaction, damage to our

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reputation, or customers switching to competitive products. Any interruption in supply could be particularly damaging to our customers using the System One to treat chronic end-stage renal disease and who need access to the System One and related disposables to continue their therapy.

Finding alternative sources for these raw materials, components, finished goods and sterilization services would be difficult and in many cases entail a significant amount of time, disruption and cost. Although we believe our supply chain has sufficient inventory of raw materials, components and finished goods to withstand a temporary disruption in supply from any single source supplier, any permanent or long-term disruption in supply from any single source supplier could lead to supply delays or interruptions which would damage our business and impair our reputation, at least in the near term.

Natural disasters, labor disputes and other adverse developments at our manufacturing facilities may cause production delays and prevent us from delivering our products on a timely basis.

We rely on our manufacturing facilities in Mexico, Italy and Germany for the production of our equipment and disposables. The loss of any of these facilities due to fire, natural disaster, war, power failure or other cause beyond our control could cause significant production delays, prevent us from meeting customer demand for our products, increase our product costs, impair our product quality or reliability, and result in substantially decreased revenues.

While we have labor agreements with our production employees in Mexico and Italy, we may experience strikes, work stoppages, work slowdowns, grievances, complaints, claims of unfair labor practices, other collective bargaining disputes, anti-union behavior, or other labor disputes at our manufacturing facilities. Some of our key single-source suppliers also have labor agreements in place, but nonetheless may be subject to similar risks related to labor disputes. Any such activity likely would cause production delays and prevent us from delivering our production commitments to customers, which could adversely affect our reputation and cause our business and operating results to suffer.

We do not have long-term supply contracts with many of our third-party suppliers.

We purchase raw materials and components from third-party suppliers, including some single-source suppliers, through purchase orders and do not have long-term supply contracts with many of our suppliers. Many of our suppliers are not obligated to perform services or supply products for any specific period, in any specific quantity or at any specific price, except as may be provided in a particular purchase order. We do not maintain large volumes of inventory from most of our suppliers. If we inaccurately forecast demand for finished goods, we may be unable to meet customer demand which could harm our competitive position and reputation. In addition, if we fail to effectively manage our relationships with our suppliers, we may be required to change suppliers, which may be time consuming and lead to disruptions in our product supply. Although we believe our supply chain has sufficient inventory of raw materials, components and finished goods to withstand a temporary disruption in supply from any single-source supplier, any permanent or long-term disruption in supply from any single-source supplier could lead to supply delays or interruptions which would damage our business and impair our reputation, at least in the near term.

Increases in the price for resin, a key material in the manufacture of our products, could impair our ability to achieve profitability.

Resin is a key material in the manufacture of our products, including the System One cartridge. We currently source resin from a small number of suppliers. Periods of rising prices for crude oil, natural gas and other petrochemical intermediates from which resin is produced have resulted in significant price increases for this material, and similar periods of rising resin prices may occur in the future. Our contracts with customers restrict our ability to immediately pass on these price increases, and future pricing to customers may be insufficient to accommodate increasing resin costs. In addition, our overall cost reduction plans may not sufficiently offset the impact of increased resin costs, which could result in declining margins and operating results.

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Increasing fuel prices could impair our ability to achieve profitability.

We currently incur significant inbound and outbound distribution costs, which are dependent upon fuel prices. Increases in fuel prices could lead to increases in our distribution costs, which could impair our ability to achieve profitability.

Failure to protect our information technology infrastructure against cyber-based attacks, network security breaches, service interruptions, or data corruption could significantly disrupt our operations and adversely affect our business and operating results.

We rely on information technology and telephone networks and systems, including the Internet, to process and transmit sensitive electronic information and to manage or support a variety of business processes and activities, including sales, billing, customer service, procurement and supply chain, manufacturing, and distribution. We use enterprise information technology systems to record, process, and summarize financial information and results of operations for internal reporting purposes and to comply with regulatory, financial reporting, legal, and tax requirements. We are also in possession of confidential patient health information. Our information technology systems, some of which are managed by third-parties, may be susceptible to damage, disruptions or shutdowns due to computer viruses, attacks by computer hackers, failures during the process of upgrading or replacing software, databases or components thereof, power outages, hardware failures, telecommunication failures, user errors or catastrophic events. Despite the precautionary measures we have taken to prevent breakdowns in our information technology and telephone systems, if our systems suffer severe damage, disruption or shutdown and we are unable to effectively resolve the issues in a timely manner, we may be subject to material remediation expenses, reputational harm, and litigation, and our business and operating results may suffer significantly.

Risks Related to Intellectual Property

If we are unable to protect our intellectual property and prevent its use by third parties, we will lose a significant competitive advantage.

We rely on patent protection, as well as a combination of copyright, trade secret and trademark laws, to protect our proprietary technology and prevent others from duplicating our products. However, these means may afford only limited protection and may not:

• prevent our competitors from duplicating our products;

• prevent our competitors from gaining access to our proprietary information and technology; or

• permit us to gain or maintain a competitive advantage.

These risks may increase in foreign countries whose laws do not protect intellectual property rights effectively or to the same extent as U.S. laws.

Any of our patents, including those we may license, may be challenged, invalidated, rendered unenforceable or circumvented. We may not prevail if our patents are challenged by competitors or other third parties. The U.S. federal courts or equivalent national courts or patent offices elsewhere may invalidate our patents, find them unenforceable, or narrow their scope. Furthermore, competitors may be able to design around our patents, or obtain patent protection for more effective technologies, designs or methods for treating kidney failure. If these developments were to occur, our products may become less competitive and sales of our products may decline.

We have filed numerous patent applications seeking protection of products and other inventions originating from our research and development. Our patent applications may not result in an issued patent, and any patents that are issued may not provide meaningful protection against competitors or competitive technologies.

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Our products could infringe the intellectual property rights of others, which may lead to costly litigation, result in substantial damages or royalty obligations, and prevent us from using technology that is essential to our products.

The medical device industry has been characterized by extensive litigation and administrative proceedings regarding patent infringement and intellectual property rights. Products to provide kidney replacement therapy have been available for more than 30 years and our competitors hold a significant number of patents relating to kidney replacement devices, therapies, products and supplies. Competitors and other third parties may allege that our products or methods infringe their patents or other intellectual property rights, and the possibility of such infringement claims may increase as our business expands into new markets.

Infringement and other intellectual property claims and proceedings brought against us, whether successful or not, could result in substantial costs and harm to our reputation. Such claims and proceedings can also divert management and key personnel from other tasks important to the success of the business. In addition, intellectual property litigation or claims could require us to:

• cease selling or using any of our products that incorporate the asserted intellectual property, which would adversely affect our revenues;

• pay substantial damages for past use of the asserted intellectual property;

• obtain a license from the holder of the asserted intellectual property, which license may not be available on reasonable terms, if at all and which could reduce profitability; and

• redesign or rename, in the case of trademark claims, our products to avoid infringing the intellectual property rights of third parties, which may not be possible and could be costly and time consuming if it is possible to do so.

Confidentiality agreements with employees and others may not adequately prevent disclosure of trade secrets and other proprietary information.

In order to protect our proprietary technology and processes, we rely in part on confidentiality agreements with our corporate partners, employees, consultants, outside scientific collaborators and sponsored researchers, advisors and others. These agreements may not effectively prevent disclosure of confidential information and trade secrets and may not provide an adequate remedy in the event of unauthorized disclosure of confidential information. In addition, others may independently discover or reverse engineer trade secrets and proprietary information, and in such cases we may be unable to assert any trade secret rights against such party. Costly and time-consuming litigation could be necessary to enforce and determine the scope of our proprietary rights, and failure to obtain or maintain trade secret protection could adversely affect our competitive position.

We may be subject to damages resulting from claims that our employees or we have wrongfully used or disclosed alleged trade secrets of other companies.

Many of our employees have worked at other medical device companies focused on the development of dialysis products, including our competitors. We may be subject to claims that these employees or we have inadvertently or otherwise used or disclosed trade secrets or other proprietary information of their former employers. Litigation may be necessary to defend against these claims. If we fail in defending such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights. Even if we are successful in defending against these claims, litigation could result in substantial costs and harm to our reputation and be a distraction to management.

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Risks Related to our Common Stock

The market price of our common stock may fluctuate significantly.

There may be periods of volatility in the market price of our common stock that delay or prevent you from selling your common stock at or above the price you paid for it. Some of the factors that may cause the market price of our common stock to fluctuate include:

• timing of market launch and market acceptance of our products;

• timing of achieving profitability from operations;

• changes in estimates of our financial results or recommendations by securities analysts or the failure to meet or exceed securities analysts’ expectations;

• actual or anticipated variations in our quarterly operating results;

• future debt or equity financings;

• developments or disputes with key vendors or customers, or adverse changes to the purchasing patterns of key customers and distributors;

• disruptions in product supply for any reason, including product recalls, our failure to appropriately forecast supply or demand, difficulties in moving products across international borders, or the failure of third party suppliers to produce needed products or components;

• reports by officials or health or medical authorities, the general media or the FDA regarding the potential benefits of the System One, similar dialysis products distributed by other companies, or more frequent or home dialysis;

• the FDA or foreign regulatory agencies and notified bodies declining to clear or approve our product candidates or to issue CE Certificates of Conformity, or delays in the FDA or other foreign regulatory agency and notified body review processes;

• product recalls and withdrawals;

• defaults under our material contracts, including without limitation our credit agreement;

• regulatory developments in the United States and foreign countries;

• changes in third-party healthcare reimbursements, particularly a decline in the level of Medicare reimbursement for dialysis treatments, or the willingness of Medicare contractors to pay for more than three treatments a week where medically justified;

• litigation involving our company or our general industry;

• announcements of technical innovations or new products by our competitors;

• developments or disputes concerning our patents or other proprietary rights;

• our ability to manufacture and supply our products to commercial standards;

• significant acquisitions, strategic partnerships, joint ventures or capital commitments by us or our competitors;

• departures of key personnel;

• investors’ general perception of our company, our products, the economy and general market conditions; and

• the other risks and uncertainties described in these “Risk Factors.”

The stock markets in general have experienced substantial volatility that has often been unrelated to the operating performance of individual companies. These broad market fluctuations may adversely affect the trading price of our common stock. In the past, following periods of volatility in the market price of a company’s

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securities, stockholders have often instituted class action securities litigation against those companies. Such litigation, if instituted, could result in substantial costs and diversion of management attention and resources, which could significantly harm our profitability and reputation.

Provisions in our governing documents and under Delaware law may discourage potential acquisition proposals and changes in management that stockholders may favor.

Provisions in our charter and bylaws and under the corporation law of Delaware, where we are incorporated, may delay or prevent a takeover attempt that could be viewed as beneficial to stockholders who wish to receive a premium for their shares from a potential bidder. These provisions may also discourage stockholders from attempting to replace or remove members of our board of directors, which in turn may delay or prevent changes in our current management team that stockholders may favor. These provisions include:

• a prohibition on stockholder actions by written consent;

• the ability of our board of directors to issue preferred stock without stockholder approval, which could be used to institute a “poison pill” that would work to dilute the stock ownership of a potential hostile acquirer, effectively preventing acquisitions that have not been approved by our board of directors;

• advance notice requirements for nominations of directors or stockholder proposals;

• the requirement that board vacancies be filled by a majority of our directors then in office; and

• the prohibition on a person who owns in excess of 15% of our outstanding voting stock from merging or combining with us for a period of three years after the date of the transaction in which the person acquired in excess of 15% of our outstanding voting stock, unless the merger or combination is approved in a prescribed manner.

If we obtain additional financing for acquisitions and other growth initiatives, it may reduce the market value of our common shares.

As part of our growth strategy, we may acquire other businesses and technologies and pursue additional business opportunities. To finance such activity, we may issue equity securities, which may dilute our existing stockholders, and incur debt, which may place restrictions on our business operations. Such financing activity may reduce the market value of our common shares and other securities, in particular if the initiatives being funded are not viewed favorably by our stockholders and are ultimately unsuccessful.

Item 1B. Unresolved Staff Comments

Not applicable.

Item 2. Properties

Our corporate headquarters are located at a facility in Lawrence, Massachusetts under a lease expiring in 2023 that will allow us to lease up to 141,000 square feet over a period of eight years. The facility is also used for research and development, general and administrative support functions, customer service and IT support services.

We have a manufacturing facility totaling 238,161 square feet in Tijuana, Mexico under leases that expire beginning in 2016 that supports both our System One and In-Center segments.

We have a 36,300 square foot manufacturing facility in Modena, Italy, a majority of which we own with the remainder subject to leases that expire beginning in 2018. This facility supports our System One and In-Center segments.

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We have a 12,369 square foot manufacturing and research and development facility in Rosdorf, Germany under a lease that expires in December 2015 and is subject to annual renewals. This facility principally supports our System One segment.

We operate a 50,110 square foot manufacturing facility owned by Asahi in Goettingen, Germany where we manufacturer products for our System One segment and for sale to Asahi.

We lease clinical and office space for all of our NxStage Kidney Care dialysis centers under leases that expire from 2018 to 2022. Our centers range in size from approximately 4,200 to 8,000 square feet, with an average size of approximately 6,300 square feet.

We believe that our existing facilities are adequate for our current needs and that suitable additional or alternative space will be available on commercially reasonable terms at such time as it becomes needed.

Item 3. Legal Proceedings

Not applicable.

Item 4. Mine Safety Disclosures

Not applicable.

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PART II

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities

Market Information

Our common stock is quoted on the NASDAQ Global Select Market under the symbol “NXTM”. The following table sets forth, for the periods indicated, the high and low sales prices of our common stock.

	High		Low
2014
First Quarter	$	15.00	$	9.92
Second Quarter	$	14.85	$	10.69
Third Quarter	$	15.65	$	11.50
Fourth Quarter	$	18.98	$	12.71
2013
First Quarter	$	12.32	$	10.35
Second Quarter	$	14.64	$	10.61
Third Quarter	$	14.51	$	12.28
Fourth Quarter	$	14.08	$	8.77

Holders

As of February 17, 2015, there were approximately 53 holders of record of our common stock.

Dividends

We have never paid or declared any cash dividends on our common stock. We anticipate that we will retain our earnings for future growth and therefore do not anticipate paying cash dividends in the foreseeable future. Our revolving line of credit with General Electric Capital Corporation and Silicon Valley Bank restricts our ability to pay cash dividends while borrowings are outstanding. For more information about this revolving line of credit, please see Note 8, Debt and Capital Lease Obligations to our consolidated financial statements included in this Annual Report.

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Comparative Stock Performance Graph

The graph below compares the five-year cumulative total stockholder return on our common stock, the Total Return Index for the NASDAQ Stock Market (U.S. Companies), which we refer to as the NASDAQ Composite Index, and the NASDAQ Medical Equipment Index assuming the investment of $100.00 on December 31, 2009 with dividends being reinvested. Measurement points are the last trading days of each quarter during such five-year period.

Issuer Purchases of Equity Securities

During November 2014, we repurchased 98,398 shares of our common stock at a price of $17.61 per share that were delivered in payment for the exercise of employee stock options. See Note 14 to our consolidated financial statements included in this Annual Report.

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Item 6. Selected Financial Data

SELECTED CONSOLIDATED FINANCIAL DATA

The following selected consolidated financial data should be read together with the information under “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and the notes to those consolidated financial statements included elsewhere in this Annual Report. The selected statements of comprehensive loss data for the years ended December 31, 2014, 2013 and 2012 and balance sheet data as of December 31, 2014 and 2013 set forth below have been derived from our audited consolidated financial statements included elsewhere in this Annual Report. The selected statements of comprehensive loss data for the years ended December 31, 2011 and 2010 and balance sheet data as of December 31, 2012, 2011 and 2010 set forth below have been derived from the audited consolidated financial statements for such years included in prior Annual Reports on Form 10-K.

	Years Ended December 31,
	2014			2013			2012			2011			2010
	(In thousands, except per share data)
Statement of Comprehensive Loss Data:
Revenues	$	301,501		$	263,429		$	242,132		$	217,256		$	179,218
Cost of revenues		185,598			160,926			149,324			139,648			121,091
Gross profit		115,903			102,503			92,808			77,608			58,127
Operating expenses:
Selling and marketing		55,385			47,842			40,485			37,550			34,166
Research and development		22,635			18,887			17,111			14,437			12,900
Distribution		26,001			21,246			18,888			17,916			14,751
General and administrative		34,069			32,326			27,530			23,206			22,774
Total operating expenses		138,090			120,301			104,014			93,109			84,591
Loss from operations		(22,187	)		(17,798	)		(11,206	)		(15,501	)		(26,464	)
Other expense, net		(873	)		(1,008	)		(2,914	)		(5,002	)		(4,480	)
Net loss before income taxes		(23,060	)		(18,806	)		(14,120	)		(20,503	)		(30,944	)
Provision for (benefit from) income taxes		1,253			(245	)		1,033			899			768
Net loss		(24,313	)		(18,561	)		(15,153	)		(21,402	)		(31,712	)
Less: Net loss attributable to noncontrolling interests		(367	)		—			—			—			—
Net loss attributable to stockholders of NxStage Medical, Inc.	$	(23,946	)		(18,561	)	$	(15,153	)	$	(21,402	)	$	(31,712	)
Net loss per share, basic and diluted	$	(0.39	)	$	(0.31	)	$	(0.26	)	$	(0.39	)	$	(0.66	)
Weighted-average shares outstanding, basic and diluted		61,700			60,261			57,890			54,217			48,188

	December 31,
	2014			2013			2012			2011			2010
	(In thousands)
Balance Sheet Data:
Cash and cash equivalents	$	52,884		$	84,134		$	106,439		$	102,909		$	104,339
Working capital		84,395			108,513			122,235			123,470			119,089
Total assets		309,726			306,962			311,949			291,708			286,094
Long-term liabilities(1)		73,415			74,594			75,126			109,723			97,574
Accumulated deficit		(387,488	)		(363,542	)		(344,981	)		(329,828	)		(308,426	)
Total stockholders’ equity(1)(2)	$	191,555		$	194,761		$	197,591		$	151,186		$	152,129

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(1) In May 2012, we repaid in full all principal and interest in the aggregate amount of $45.2 million under our term loan and security agreement with Asahi through the issuance of 2.5 million shares of our common stock.

(2) In November 2010, we issued and sold 3.7 million shares of common stock pursuant to an underwriting agreement with Canaccord Genuity. Net proceeds from the sale were $73.4 million.

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

Overview

The results of our operations are included in three separately reportable business segments, System One, In-Center, and Services. Other business activities relate primarily to the manufacturing of dialyzers for sale to Asahi, and research and development and general and administrative expenses that are excluded from the segment operating performance measures. In the System One segment we derive our revenues from the sale and rental of the System One and PureFlow SL dialysate preparation equipment and the sale of disposable products in the home and critical care markets. The home market is devoted to the treatment of ESRD patients in the home or a home-like setting, while the critical care market is devoted to the treatment of hospital-based patients with acute kidney failure or fluid overload. In the In-Center segment, we derive our revenues from the sale of blood tubing sets and needles for hemodialysis primarily for the treatment of ESRD patients at dialysis centers, and needles for apheresis. Our Services segment includes revenues from dialysis services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

Financial Performance

The following table summarizes our consolidated results (in thousands, except percentages).

	Twelve Months Ended December 31,
	2014			2013			2012
System One, In-Center and Other
Revenues	$	300,598		$	263,077		$	242,132
Gross profit	$	123,011		$	103,295		$	92,808
Gross margin percentage		41	%		39	%		38	%
Loss from operations	$	(7,261	)	$	(12,108	)	$	(9,988	)
Services
Revenues	$	1,749		$	352		$	—
Gross profit	$	(7,108	)	$	(792	)	$	—
Gross margin percentage		n/a			n/a			n/a
Loss from operations	$	(14,926	)	$	(5,690	)	$	(1,218	)
Eliminations
Elimination of intersegment revenues	$	(846	)	$	—		$	—
Total Company
Revenues	$	301,501		$	263,429		$	242,132
Gross profit	$	115,903		$	102,503		$	92,808
Gross margin percentage		38	%		39	%		38	%
Loss from operations	$	(22,187	)	$	(17,798	)	$	(11,206	)

For several years, we have focused on operating and financial improvements. These efforts resulted in annual revenue growth of 14% during 2014 and 9% during 2013, with our home and critical care markets each driving growth. While driving continued improvements will remain an area of focus in 2015 and beyond within our System One and In-Center segments, at the same time, we expect to make significant investments in our

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Services segment. We expect that these investments will have a negative impact on our total operating performance in the near term and may offset performance improvements we expect in our System One and In-Center segments.

Statement of Comprehensive Loss Components

Revenues

In the System One segment we derive our revenues from the sale and rental of equipment and the sale of disposable products in the home and critical care markets. In the home market, customers purchase or rent the System One equipment, including cycler and PureFlow SL, and then purchase the related disposable products based on a specific patient prescription. In the critical care market, we sell or rent the System One and sell related disposables to hospital customers. In the In-Center segment, we derive our revenues from the sale of needles and blood tubing sets. Nearly all of our sales in the In-Center segment are through supply and distribution contracts with distributors. Our Services segment includes revenues from dialysis services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

In the home market, the majority of our revenue is derived from recurring sales of disposable products. For customers that purchase the System One, we recognize revenue from the equipment sale ratably over the expected service obligation period. For customers that rent the System One, we recognize revenue on a monthly basis. We recognize revenues related to the disposable products upon delivery. Over time, as more home patients are treated with the System One and more systems are placed in patient homes, we expect to derive a growing recurring revenue stream from the sale of related disposables.

Our contracts with dialysis centers in the home market for ESRD home dialysis patients generally include terms providing for the sale of disposable products to accommodate up to the number of prescribed treatments per month per patient and the purchase or monthly rental of System One cyclers and, in most instances, our PureFlow SL equipment. These contracts typically have a term of one to seven years, and may be renewed on a month-to-month basis thereafter, subject to a 30-day termination notice. Under these contracts, if home hemodialysis is prescribed, supplies are shipped directly to patient homes and paid for by the treating dialysis center. We also include vacation delivery terms, providing for the shipment of products to a designated vacation destination for a specified number of vacation days. We derive a small amount of revenues from the sale of supplementary products and services such as equipment maintenance and service fees, ancillaries, reserve inventory and special deliveries.

In the critical care market we recognize revenues upon delivery in accordance with contract terms. Our contracts with hospitals generally include terms providing for the sale of our System One equipment and disposables, although we also provide an equipment rental option. These contracts typically have a term of one year. We derive a small amount of revenues from the sale of one- and two-year service contracts following the expiration of our standard one-year warranty period for System One equipment. To further support service in the critical care market, we have a bio-medical training program, whereby we train bio-medical engineers on how to service and repair certain aspects of the System One in the critical care setting. Bio-medical training is typically provided under a two-year contract following the expiration of our standard one-year warranty period for System One equipment. As more System One equipment is placed within hospitals, we expect to continue to derive a growing recurring revenue stream from the sale of disposable cartridges and fluids as well as, to a much lesser degree, from service and bio-medical training contracts.

In the In-Center segment nearly all sales to end users are structured through supply and distribution contracts with several significant distributors; however, in many instances we have direct contractual relationships with our end user customers. These contracts typically contain minimum volume commitments with negotiated pricing triggers at different volume tiers. Revenue is recognized upon delivery in accordance with contract terms.

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The majority of our revenues have been generated from sales to customers in the U.S. We sell our System One and certain of our other products internationally through direct sales in the UK and Canada and through distributors in other countries. We recognize revenues from equipment sales to our international distributors at the time of shipment or, if applicable, delivery in accordance with contract terms. Disposable product revenues are recognized upon delivery. We also manufacture and sell dialyzers to Asahi and recognize revenues at the time of shipment in accordance with contract terms.

Revenues in our Services segment are derived from dialysis care services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

We offer certain customers rebates based on sales to specific end users and discounts for early payment. Our revenues are presented net of these rebates and discounts. For our System One segment, as of December 31, 2014, we had $2.0 million reserved against trade accounts receivable for future rebates and discounts and recorded $9.1 million, $6.8 million and $5.5 million during 2014, 2013 and 2012, respectively, as a reduction of revenues in connection with rebates and discounts. For our In-Center segment, as of December 31, 2014, we had $4.4 million reserved against trade accounts receivable for future rebates and discounts and recorded $8.7 million, $6.9 million, and $6.4 million during 2014, 2013 and 2012, respectively, as a reduction of revenues in connection with rebates and discounts.

Cost of Revenues

Cost of revenues consists primarily of direct product costs, material and labor required to manufacture our products, service of System One equipment that we sell or rent to customers and manufacturing overhead. It also includes the cost of servicing, repairing, and inspecting System One equipment prior to sale or during the warranty period, patient care costs at our NxStage Kidney Care dialysis centers and stock-based compensation for certain personnel. The cost of our products depends on several factors, including the efficiency of our manufacturing operations, the cost at which we can obtain labor and products from third-party suppliers, product reliability and related servicing costs and the design of our products.

Operating Expenses

Selling and Marketing.    Selling and marketing expenses consist primarily of salary, benefits and stock-based compensation for sales, marketing, and business development personnel, travel, promotional and marketing materials and other expenses associated with providing clinical training to our customers. Included in selling and marketing are the costs of clinical educators, usually nurses, we employ to teach our customers about our products and prepare our customers to instruct their patients and their partners in the operation of our products, customer service and technical support personnel. Also included in this category are the personnel and other costs associated with our market development activities to establish, develop and operate NxStage Kidney Care dialysis centers, including administrative support functions directly related to the startup and support of this initiative.

Research and Development.    Research and development expenses consist primarily of salary, benefits and stock-based compensation for research and development personnel, supplies, materials and expenses associated with product design and development, clinical studies, regulatory submissions, reporting and compliance and expenses incurred for outside consultants or firms who furnish services related to these activities.

Distribution.    Distribution expenses include the freight costs of delivering our products to our customers or our customers’ patients, depending on the market and the specific agreements with our customers, salary, benefits and stock-based compensation for distribution personnel and the cost of any equipment lost or damaged in the distribution process. We use common carriers and freight companies to deliver our products and do not operate our own delivery service. Also included in this category are the expenses of shipping products under warranty from customers back to our service center for repair and the related expense of shipping a replacement product to our customers or their patients.

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General and Administrative.    General and administrative expenses consist primarily of salary, benefits and stock-based compensation for our executive management, legal and finance and accounting staff, fees of outside legal counsel, fees for our annual audit and tax services, and general expenses to operate the business, including insurance and other corporate-related expenses. Also included in general and administrative expenses, beginning in 2013, are tax expenses incurred related to the medical device excise tax.

Comparison of Years Ended December 31, 2014 and 2013

Revenues

Our revenues for 2014 and 2013 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2014					2013
System One segment
Home	$	157,822		52	%	$	132,944	50	%
Critical Care		55,609		19	%		43,812	17	%
Total System One segment		213,431		71	%		176,756	67	%
In-Center segment		78,885		26	%		81,852	31	%
Other		8,282		3	%		4,469	2	%
Products subtotal		300,598		100	%		263,077	100	%
Services segment		1,749		—	%		352	—	%
Elimination of intersegment revenues		(846	)	—	%		—	—	%
Total	$	301,501		100	%	$	263,429	100	%

In the home market, revenues increased $24.9 million, or 19%, during 2014 compared to 2013. This increase was driven primarily by the increase in the number of patients prescribed to use the System One both in the U.S. and internationally. We expect future demand for our products and revenue growth in the home market to be strong as we further penetrate this market, both in the U.S. and internationally, and leverage the annuity nature of our business. As our international business grows, our System One revenue will be susceptible to fluctuations in equipment sales and changes in inventory levels at our international distributors.

Critical care market revenues increased $11.8 million, or 27%, during 2014 compared to 2013, driven by higher sales of disposables from our growing base of System One equipment placed with our customers coupled with increased sales of System One equipment. We expect future demand for our products and revenue growth to be strong as we seek to further penetrate this market and leverage the annuity nature of our business. However, sales of our System One equipment in the critical care market may fluctuate due to timing of sales and the overall capital spending environment of our customers.

In-Center segment revenues decreased $3.0 million, or 4%, during 2014 compared to 2013, driven by lower needle sales consistent with the wind down of the DaVita needle purchase agreement, contractual pricing and changes in inventory levels at our distributors. In-Center segment revenues are expected to decrease at least in the near term as a result of the expiration of DaVita’s needle purchase agreement in December 2014. Additionally, future revenues will fluctuate as a result of increased competition and variations in inventory management policies with both our distributors and end users.

Other revenues for 2014 and 2013 relate primarily to dialyzers sold to Asahi which have increased as we continue to ramp-up production capacity at the new manufacturing plant in Germany which commenced operations in late 2012. Sales to Asahi may fluctuate due to timing of sales, inventory management policies at Asahi and changes in currency rates.

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Service segment revenues for 2014 and 2013 relate to dialysis services provided to patients at our recently opened NxStage Kidney Care dialysis centers. We expect future revenues to increase modestly as we work towards attracting additional patients to our centers.

Gross Profit (Loss)

Our gross profit (loss) and gross profit (loss) as a percentage of revenues for 2014 and 2013 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2014					2013
System One segment	$	102,420		48	%	$	80,585		46	%
In-Center segment		20,765		26	%		24,088		29	%
Subtotal		123,185		42	%		104,673		40	%
Other		(174	)	n/a			(1,378	)	n/a
Products subtotal		123,011		41	%		103,295		39	%
Services segment		(7,108	)	n/a			(792	)	n/a
Gross profit	$	115,903		38	%	$	102,503		39	%

Gross profit as a percentage of revenues for the System One segment increased versus 2013 driven by favorable product mix, contractual price improvements, and manufacturing efficiencies, partially offset by higher product and service costs and unfavorable currency exchange rate changes versus the U.S. Dollar. We expect to continue to see improvements in gross profit as a percentage of revenue in our System One segment as we lower costs through process improvements and product design changes, increase volume, and rationalize our manufacturing operations.

Gross profit as a percentage of revenues for the In-Center segment decreased versus 2013 driven primarily by contractual pricing and lower volumes. We expect gross profit as a percentage of revenues to decline, at least in the near term, as a result of changes in product mix.

The Other category relates to costs associated with the manufacturing of dialyzers for sale to Asahi, which should provide us with long term cost efficiencies through increased dialyzer production volumes. These cost efficiencies may be offset in the short-term as we incur additional costs to expand capacity in this facility.

The negative gross profit as a percentage of revenues incurred by our Services segment was driven by costs associated with starting up our NxStage Kidney Care dialysis centers. We expect the Services segment gross margin will continue to be negatively impacted by costs associated with the development of our NxStage Kidney Care dialysis centers.

In aggregate, total company gross profit as a percentage of revenues will be negatively impacted, at least in the near-term, by costs associated with our continued investment in our Services segment and may be offset by other factors including increased freight costs and services costs and unfavorable product mix.

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Selling and Marketing

Our selling and marketing expenses and selling and marketing expenses as a percentage of revenues for 2014 and 2013 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2014				2013
System One segment	$	41,763	20	%	$	37,691	21	%
In-Center segment		5,804	7	%		5,253	6	%
Products subtotal		47,567	16	%		42,944	16	%
Services segment		7,818	n/a			4,898	n/a
Total Selling and marketing	$	55,385	18	%	$	47,842	18	%

Selling and marketing expenses increased $7.5 million, or 16%, during 2014 compared to 2013 but remained consistent as a percentage of revenues.

Selling and marketing expenses for the System One and In-Center segments increased due to increased personnel and personnel-related costs and increased spending due to expanded marketing programs but remained consistent in total as a percentage of revenues during 2014 compared to 2013.

Selling and marketing expenses for our Services segment increased due to increased expenses for personnel and other costs associated with our market development activities to establish, develop and operate NxStage Kidney Care dialysis centers, including administrative support functions directly related to the startup and support of this initiative.

We anticipate that selling and marketing expenses will continue to increase but remain relatively consistent as a percentage of revenues as we broaden our marketing and market development initiatives, including with respect to NxStage Kidney Care, increase public awareness of the System One in the home market and support growth in international markets.

Research and Development

Our research and development expenses and research and development expenses as a percentage of revenues for 2014 and 2013 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2014				2013
Research and development	$	22,635	8	%	$	18,887	7	%

Research and development expenses increased $3.7 million, or 20%, during 2014 compared to 2013. The increase was primarily due to increased personnel and personnel-related costs and increased project related spending. Further, research and development costs for 2013 included a incremental benefit of $0.4 million related to the recognition of a tax incentive received from the Massachusetts Life Sciences Center.

For the near term, we expect research and development expenses will increase as we seek to further develop and enhance the System One, invest in our next generation hemodialysis system, invest in our peritoneal dialysis product development program and expand our product portfolio but will remain consistent as a percentage of revenues.

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Distribution

Our distribution expenses and distribution expenses as a percentage of revenues for 2014 and 2013 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2014				2013
System One segment	$	23,855	11	%	$	18,858	11	%
In-Center segment		2,146	3	%		2,388	3	%
Total Distribution	$	26,001	9	%	$	21,246	8	%

Distribution expenses increased $4.8 million, or 22%, during 2014 compared to 2013 driven mainly by increased shipment volumes; however, it has remained relatively consistent as a percentage of revenues during 2014 compared to 2013 in both segments. We expect that distribution expenses will remain consistent as a percentage of revenues at least in the near term.

General and Administrative

Our general and administrative expenses and general and administrative expenses as a percentage of revenues for 2014 and 2013 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2014				2013
General and administrative	$	34,069	11	%	$	32,326	12	%

General and administrative expenses increased $1.7 million, or 5%, during 2014 compared to 2013. The increase in general and administrative expenses was due to increased personnel and personnel-related costs and other related infrastructure costs and higher medical device excise tax expense driven by an increase in the amount of our products sold on which the tax is assessed, partially offset by lower professional service fees.

Other Expense

Interest expense increased $0.3 million during 2014 compared to 2013. Interest expense includes interest costs and other fees related to our debt obligations, including our capital lease obligations.

The change in other expense, net is derived primarily by foreign currency gains and losses.

Provision for Income Taxes

We recognized a provision for income taxes during 2014 and 2013 related to the profitable operations of certain foreign subsidiaries. However, the 2013 provision was offset by the recognition of a $1.2 million gain resulting from the favorable conclusion of a foreign income tax audit and a gain related to a foreign legislative change. Refer to Note 11, Income Taxes, to our consolidated financial statements included in this Annual Report for further discussion of our tax positions.

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Comparison of Years Ended December 31, 2013 and 2012

Revenues

Our revenues for 2013 and 2012 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2013				2012
System One segment
Home	$	132,944	50	%	$	123,589	51	%
Critical Care		43,812	17	%		39,540	16	%
Total System One segment		176,756	67	%		163,129	67	%
In-Center segment		81,852	31	%		76,927	32	%
Other		4,469	2	%		2,076	1	%
Products subtotal		263,077	100	%		242,132	100	%
Services segment		352	—	%		—	—	%
Elimination of intersegment revenues		—	—	%		—	—	%
Total	$	263,429	100	%	$	242,132	100	%

In the home market, revenues increased $9.4 million, or 8%, during 2013 compared to 2012, driven by the increase in the number of patients prescribed to use, and centers offering, the System One, partially offset by lower deferred revenue recognized on previously sold System One equipment in the U.S. home market as a result of equipment reaching the end of its related revenue amortization period. These results also reflect a one-time reduction in revenue due to the transition of our UK business to a direct sales model from a distributor relationship in the first quarter of 2013. We have increased both the number of patients at existing centers and centers offering the System One, primarily through our existing relationships with service providers, including DaVita and Fresenius, and through our direct to patient marketing efforts. Critical care market revenues increased $4.3 million, or 11%, during 2013 compared to 2012, driven by higher sales of System One disposables and equipment. Sales of our System One equipment in the critical care market may fluctuate due to timing of sales and the overall capital spending environment.

In-Center segment revenues increased $4.9 million, or 6%, during 2013 compared to 2012, driven by increased end user demand and contractual price improvements.

Other revenues for 2013 and 2012 relate primarily to dialyzers sold to Asahi.

Service segment revenues relate to dialysis services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

Gross Profit

Our gross profit (loss) and gross profit (loss) as a percentage of revenues for 2013 and 2012 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2013					2012
System One segment	$	80,585		46	%	$	74,402		46	%
In-Center segment		24,088		29	%		19,153		25	%
Subtotal		104,673		40	%		93,555		39	%
Other		(1,378	)	n/a			(747	)	n/a
Products subtotal		103,295		39	%		92,808		38	%
Services segment		(792	)	n/a			—		n/a
Gross profit	$	102,503		39	%	$	92,808		38	%

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Gross profit increased $9.7 million, or 10%, and increased as an overall percentage of revenue during 2013 compared to 2012.

Gross profit in the System One segment increased $6.2 million or 8% versus 2012 as a result of increased revenue. Gross profit as a percentage of revenue was negatively impacted by costs associated with the start-up of the new dialyzer plant in Germany. Gross profit for the In-Center segment increased $4.9 million, or 26%. In addition to the impact of increased revenues, the improvement of gross profits and gross profit as a percentage of revenues in the In-Center segment was attributable to contractual price improvements and lower manufacturing costs, including the non-recurrence of costs incurred during 2012 associated with the transition of certain blood tubing sets from a contract manufacturer to our own manufacturing plant.

The Other category relates to the manufacturing of dialyzers for sale to Asahi, which should provide us with long-term cost efficiencies through increased dialyzer production volumes.

The Services segment includes the costs associated with establishing and operating our NxStage Kidney Care dialysis centers.

Selling and Marketing

Our selling and marketing expenses and selling and marketing expenses as a percentage of revenues for 2013 and 2012 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2013				2012
System One segment	$	37,691	21	%	$	33,728	21	%
In-Center segment		5,253	6	%		5,539	7	%
Products subtotal		42,944	16	%		39,267	16	%
Services segment		4,898	n/a			1,218	n/a
Total Selling and marketing	$	47,842	18	%	$	40,485	17	%

Selling and marketing expenses increased $7.4 million, or 18%, during 2013 compared to 2012.

Selling and marketing expenses for the System One and In-Center segments increased due to increased personnel and personnel-related costs and increased spending due to expanded marketing programs but remained relatively consistent as a percentage of revenues during 2013 compared to 2012 as we continued to leverage our infrastructure.

Selling and marketing expenses for our Services segment relates personnel and other costs associated with our market development activities to establish, develop and operate NxStage Kidney Care dialysis centers, including administrative support functions directly related to the startup and support of this initiative.

Research and Development

Our research and development expenses and research and development expenses as a percentage of revenues for 2013 and 2012 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2013				2012
Research and development	$	18,887	7	%	$	17,111	7	%

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Research and development expenses increased $1.8 million, or 10%, during 2013 compared to 2012 but remained consistent as a percentage of revenues. The increase was primarily due to increased personnel and personnel-related costs and increased project related spending partially offset by the recognition of $0.7 million during 2013 of a tax incentive received from the Massachusetts Life Sciences Center.

Distribution

Our distribution expenses and distribution expenses as a percentage of revenues for 2013 and 2012 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2013				2012
System One segment	$	18,858	11	%	$	16,325	10	%
In-Center segment		2,388	3	%		2,563	3	%
Total Distribution	$	21,246	8	%	$	18,888	8	%

Distribution expenses increased $2.4 million, or 13%, during 2013 compared to 2012 due to increased business volumes but remained relatively consistent as a percentage of revenues. Increased costs due to higher volumes and expanded delivery services in the System One segment were offset by distribution network efficiencies.

General and Administrative

Our general and administrative expenses and general and administrative expenses as a percentage of revenues for 2013 and 2012 were as follows (in thousands, except percentages):

	Years Ended December 31,
	2013				2012
General and administrative	$	32,326	12	%	$	27,530	11	%

General and administrative expenses increased $4.8 million, or 17%, during 2013 compared to 2012. The increase in general and administrative expenses was primarily the result of the medical device excise tax assessed on nearly all of our products sold in the U.S. beginning in 2013 and increased professional service fees and other related infrastructure costs.

Other Income and Expense

Interest expense decreased $2.2 million during 2013 compared to 2012. In May 2012, we repaid our term loan with Asahi through the issuance of shares of our common stock.

The change in other expense, net is derived primarily by foreign currency gains and losses.

Provision for Foreign Income Taxes

We recognized a benefit from taxes of $(0.2) million in 2013 compared to a provision for income taxes of $1.0 million in 2012. We recorded income tax expense during both 2013 and 2012 for certain profitable foreign subsidiaries. The net benefit from income taxes recorded during 2013 includes the favorable conclusion of a foreign income tax audit during the second quarter, offset in part by additional reserves recorded for other uncertain tax positions.

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Liquidity and Capital Resources

We have operated at a loss since our inception in 1998. As of December 31, 2014, our accumulated deficit was $387.5 million and we had cash and cash equivalents of $52.9 million, with nearly all of that cash located in the U.S., and working capital of $84.4 million.

We expect to make continued improvements in cash flows driven by the improved combined performance of our System One and In-Center segments, as a result of revenue growth, operating leverage and improving profitability. Over the long term we expect to generate positive cash flow from the combined performance of these segments. We have made a significant investment of cash in our Services segment to open 11 NxStage Kidney Care dialysis centers in 2014. We currently do not expect any significant additional capital expenditures for our Services segment in 2015 beyond what is required to reach our target of 15 open centers. In the near term, these investments will offset the improvements we expect to achieve in our System One and In-Center segments. We believe, based on current projections and the current nature of our business, that we have the required resources to fund our ongoing operating requirements, which include selling and marketing activities to increase public awareness of the System One, our research and development activities to develop new products and enhance our existing products, and our planned investments in NxStage Kidney Care. If we determine that additional investment in these or any other initiatives would be beneficial, we may choose to access the credit or capital markets to provide additional liquidity. However, we can provide no guarantees that we would be successful in securing such additional financing.

Our ongoing cash requirements include funding normal working capital requirements including inventory and field equipment assets. Field equipment assets include System One equipment rented to customers in the home market and our “service pool” of equipment, which is equipment owned and maintained by us that is swapped for equipment owned or rented by our customers that needs repair or maintenance. While a majority of our home market customers have committed to purchase, rather than rent, the significant majority of their future System One equipment requirements, thereby reducing our working capital cash requirements, there can be no assurance that we will be able to continue to expand or sustain this level of equipment placements that are purchased rather than rented. Additionally, any excess rental or service swap equipment would increase our working capital requirements.

We have a revolving credit facility with General Electric Capital Corporation, or GECC, and SVB that allows for borrowing up to $35 million that expires in June 2019. Availability of credit is subject to a borrowing base that is calculated with reference to certain of our accounts receivable, inventory and equipment, and adjustments to such borrowing base are at the discretion of the lenders. The revolving credit facility requires us to comply with certain covenants while borrowings are outstanding, contains events of default customary for a transaction of this type and is secured by substantially all of our assets. As of December 31, 2014, there were no outstanding borrowings under the revolving credit facility, we were in compliance with all applicable covenants and, subject to the lenders’ adjustments described above, we had approximately $28 million of credit commitment available for borrowing.

We have two mortgages collateralized by a manufacturing facility in Italy that we acquired in May 2013 with interest rates of 6.0% and 2.0% payable over a 10-year period.

We maintain postemployment benefit plans for employees in certain foreign subsidiaries. The plans provide lump sum benefits, payable based on statutory regulations for voluntary or involuntary termination. Where required, we obtain an annual actuarial valuation of the benefit plans. We have recorded a liability of $1.7 million and $1.8 million at December 31, 2014 and 2013, respectively, for costs associated with these plans. The expense recorded in connection with these plans was not significant during 2014, 2013 or 2012.

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The following table sets forth the components of our cash flows for the periods indicated (in thousands):

	Years Ended December 31,
	2014			2013
	(In thousands)
Net cash used in operating activities	$	(20,273	)	$	(10,141	)
Net cash used in investing activities		(20,097	)		(18,480	)
Net cash provided by financing activities		9,461			5,755
Foreign exchange effect on cash and cash equivalents		(341	)		561
Net cash flow	$	(31,250	)	$	(22,305	)

Net cash used in operating activities.    Net cash used in operating activities increased by $10.1 million during 2014, versus 2013 driven by higher net loss and higher working capital requirements including increased inventory requirements to support our growth and new product offerings and higher outstanding accounts receivable from customers. We expect working capital to fluctuate due to various factors including inventory requirements and timing of payments from our customers and to our vendors.

Cash flow from deferred revenues improved by $3.9 million during 2014 as compared to 2013 as a result of increased System One equipment sales. Amortization of deferred revenues into revenues relating to sales of home equipment was $18.1 million during 2014 and $18.2 million during 2013.

Non-cash transfers from inventory to field equipment for the placement of units with our customers increased $11.5 million during 2014 compared to 2013. Non-cash transfers from field equipment to deferred costs of revenues increased $2.9 million during 2014 compared to 2013. The increase in field equipment was driven by an expansion of our service pool which we expect to normalize in the near term, increased rental activity, including that associated with our NxStage Kidney Care dialysis centers, and new product introductions.

Net cash used in investing activities.    For each of the periods above, net cash used in investing activities reflected purchases of property and equipment, primarily for the build-out of NxStage Kidney Care dialysis centers coupled with expenditures for our manufacturing facilities as a result of our efforts to rationalize and expand our manufacturing operations, along with purchases of equipment for research and development and information technology. The increase of $3.9 million in purchases of property and equipment was driven by spending related to the build-out of our NxStage Kidney Care dialysis centers. Capital expenditures for our Kidney Care centers were $13.5 million and $3.9 million during 2014 and 2013, respectively. Net cash used in investing activities during 2013 also includes $2.2 million of cash paid to Kimal in connection with our acquisition of substantially all of the System One assets of Kimal on April 2, 2013.

Net cash provided by financing activities.    During 2014 and 2013 we received $11.1 million and $5.5 million, respectively, of proceeds from stock option and stock purchase plans. Proceeds from stock option and purchase plans are subject to fluctuation based on the number of option exercised and, to a lesser extent, the weighted-average exercise price. We also received $0.9 million during 2014 and $0.5 million during 2013 of contributions from noncontrolling interest in connection with NxStage Kidney Care joint ventures. Cash provided by financing activity during 2013 included $1.1 million of proceeds from the issuance of debt in connection with financing the acquisition of a manufacturing facility in Italy. Cash provided by financing activities during both 2014 and 2013 was reduced by cash used to pay our capital lease obligations. Further, our cash provided by financing activities during 2014 was reduced by $1.1 million due to costs associated with obtaining our new revolving credit facility.

Off-Balance Sheet Arrangements

We do not have any significant off-balance sheet arrangements.

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Contractual Obligations

The following table summarizes our contractual commitments as of December 31, 2014 and the effect those commitments are expected to have on liquidity and cash flow in future periods (in thousands):

	Payments Due By Period
	Total		Less Than One Year		1-3 Years		3-5 Years		More Than 5  Years
Capital lease obligations	$	17,985	$	2,326	$	4,237	$	2,357	$	9,065
Operating leases		29,473		4,412		8,634		7,904		8,523
Debt		1,099		129		259		259		452
Purchase obligations		87,684		42,482		27,263		17,939		—
Total	$	136,241	$	49,349	$	40,393	$	28,459	$	18,040

Our capital lease obligations include our capital lease obligation due to Asahi related to a manufacturing facility in Germany along with $6.6 million representing the estimated residual value of the manufacturing facility in Germany at the end of the estimated lease term which only becomes due and payable at Asahi’s option if we terminate our agreement with Asahi.

Our purchase obligations include purchase commitments for System One components, primarily for equipment and fluids along with needles for our In-Center segment pursuant to contractual agreements with several of our suppliers that are in the normal course of business. Certain of these commitments may be extended and/or canceled at our option.

The contractual commitments included in the table above do not include postemployment benefit obligations and unrecognized tax benefits. We maintain postemployment benefit plans for employees in certain foreign subsidiaries and may be required to make cash outlays related to the settlement of these obligations. However, the timing of such cash outlays is uncertain. Please see Note 12, Stock Plans and Stock-Based Compensation to our consolidated financial statements included in this Annual Report for further details. We may be required to make cash outlays related to our unrecognized tax benefits. However, we are unable to make reasonably reliable estimates of the period of cash settlement, if any, with the respective taxing authorities. Please see Note 11, Income Taxes to our consolidated financial statements included in this Annual Report for further details.

Summary of Critical Accounting Policies and Estimates

Our discussion and analysis of our financial condition and results of operations are based upon our consolidated financial statements, which have been prepared in accordance with GAAP. Certain immaterial reclassifications have been made to prior periods’ financial statements to conform to the 2014 presentation. The preparation of these consolidated financial statements requires us to make significant estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses. These items are regularly monitored and analyzed by management for changes in facts and circumstances, and material changes in these estimates could occur in the future. Changes in estimates are recorded in the period in which they become known. We base our estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances. Actual results may differ substantially from our estimates.

Note 2, Summary of Significant Accounting Policies to our consolidated financial statements included in this Annual Report describes the significant accounting policies used in the preparation of our consolidated financial statements. A summary of those accounting policies and estimates that we believe are most critical to fully understanding and evaluating our financial results is set forth below. This summary should be read in conjunction with our consolidated financial statements and the related notes included elsewhere in this Annual Report.

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Revenue Recognition

We recognize revenue from product sales and services when earned. Revenues are recognized when: (a) there is persuasive evidence of an arrangement, (b) the product has been shipped or services and supplies have been provided to the customer, (c) the sales price is fixed or determinable and (d) collection is reasonably assured.

Certain agreements with distributors allow for product returns and credits. For shipment of product sold to distributors, revenue is recognized at the time of sale if a reasonable estimate of future returns or credit can be made. If a reasonable estimate of future returns or credit cannot be made, we recognize revenue using the “sell-through” method. Under the “sell-through” method, revenue and related costs of revenue is deferred until the final resale of such products to end customers.

In addition to contractually determined volume discounts, in many agreements we offer rebates based on sales to specific end customers and discounts for early payment. Rebates and discounts are recorded as a reduction of sales and trade accounts receivable, based on our best estimate of the amount of probable future rebate or discount on current sales.

We enter into multiple-element arrangements that may include a combination of equipment, related disposables and services. Revenue arrangements with multiple elements are divided into separate units of accounting if specified criteria are met, including whether the delivered element has stand-alone value to the customer, the consideration received is allocated among the separate units based on their respective selling price, and the applicable revenue recognition criteria are applied to each of the separate units.

We determine selling price using vendor specific objective evidence (“VSOE”), if it exists, otherwise third-party evidence of selling price is used. If neither VSOE nor third-party evidence of selling price exists for a unit of accounting, we use best estimated selling price (“BESP”). We generally expect that we will not be able to establish third-party evidence due to the nature of our products and the markets in which we compete, and, as such, we typically will determine selling price using VSOE or BESP.

We determine BESP for an individual element based on consideration of both market and Company-specific factors, including the selling price and profit margin for similar products, the cost to produce the deliverable and the anticipated margin on that deliverable and the characteristics of the varying markets in which the deliverable is sold.

System One Segment

We derive revenue in the home market from the sales of hemodialysis therapy to customers in which the customer either purchases or rents the System One and/or PureFlow SL hardware and purchases a specified number of disposable products and service.

For customers that purchase the System One and PureFlow SL hardware, in the U.S. home market, due to the depot service model whereby equipment requiring service is picked up and a replacement device is shipped to the site of care, we recognize fees received from equipment sale as revenue on a straight-line basis over the expected term of our remaining service obligation and direct costs relating to the delivered equipment are deferred and amortized over the same expected period as the related revenue. Disposable products revenue is recognized on a monthly basis upon delivery.

Under the rental arrangements revenue is recognized on a monthly basis in accordance with agreed upon contract terms and pursuant to binding customer purchase orders and fixed payment terms.

Our sales arrangements with our international distributors are structured as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms.

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In the critical care market, we structure sales of the System One and disposable products as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Certain of these arrangements provide for training, technical support and extended warranty services to our customers. We recognize training and technical support revenue when the related services are performed. In the case of extended warranty, the service revenue is recognized ratably over the extended warranty period.

In-Center Segment

Our In-Center segment sales are structured as direct product sales primarily through distributors, and we have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Some of our distribution contracts for the In-Center segment contain minimum volume commitments with negotiated pricing discounts at different volume tiers. Each agreement may be canceled upon a material breach, subject to certain curing rights, and in many instances minimum volume commitments can be reduced or eliminated upon certain events.

Services Segment

Revenues in our Services segment are derived from dialysis care services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

Revenues are recognized based on a customary fee schedule, net of estimated contractual allowances to reflect the estimated amounts to be received from the payor. Revenues are recognized in the period in which services are provided when we have the ability to reasonably estimate amounts ultimately collectible from the payor. In instances where we do not have the ability to reasonably estimate amounts ultimately collectible, as is often the case with non-contracted commercial health plans and amounts due from patients (including co-pay and deductible amounts), revenue is recognized in the period in which cash is received.

Inventory Valuation

Inventories are valued at the lower of cost or estimated market value. We regularly review our inventory quantities on hand and related cost and record a provision for excess or obsolete inventory primarily based on remaining shelf-life and estimated forecast of product demand. We also review our inventory value to determine if it reflects lower of cost or market, with market determined based on net realizable value. Appropriate consideration is given to inventory items sold at negative gross margins, purchase commitments and other factors in evaluating net realizable value. The medical device industry is characterized by rapid development and technological advances as well as regulatory and quality manufacturing guidelines that could result in obsolescence of inventory. Additionally, our estimates of future product demand may prove to be inaccurate.

Field Equipment

Field equipment consists of equipment being utilized under disposable-based rental agreements as well as “service pool” cyclers. Service pool cyclers are cyclers owned and maintained by us that are swapped for cyclers that need repairs or maintenance by us while being rented or owned by a patient. We continually monitor the number of cyclers in the service pool, as well as cyclers that are in-transit or otherwise not being used by a patient, and assess whether there are any indicators of impairment for such equipment. We also review field equipment carrying value for reasonableness. We consider factors such as actual equipment disposals and our ability to verify the equipment’s existence in the field to identify lost equipment. Charges for lost equipment are included in distribution expenses. Repairs and maintenance expenses are recorded in cost of revenues and expensed as incurred.

We capitalize field equipment at cost and depreciate field equipment through cost of revenues using the straight-line method over an estimated useful life. We review the estimated useful life of our field equipment

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periodically for reasonableness and make changes when appropriate. Factors considered in determining the reasonableness of the useful life include expected future design improvements, equipment age and actual equipment disposals.

Accounting for Stock-Based Awards

Stock-based compensation expense is estimated as of the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which generally equals the vesting period, based on the number of awards that are expected to vest. Estimating the fair value for stock options requires judgment, including the expected term of our stock options, volatility of our stock, expected dividends, risk-free interest rates over the expected term of the options and the expected forfeiture rate. In connection with our performance based programs, we make assumptions principally related to the number of awards that are expected to vest after assessing the probability that certain performance criteria will be met.

Valuation of Intangibles and Other Long-Lived Assets

For our long-lived assets including intangible assets, we assess the carrying value of these assets whenever events or changes in circumstances indicate that the carrying value may not be recoverable. Factors we consider important include, but are not limited to, significant underperformance relative to historical or projected future results, significant negative industry factors and significant changes in strategy or operations that negatively affect the utilization of our long-lived assets. If an impairment review is triggered, we evaluate the carrying value of intangible assets based on estimated undiscounted future cash flows over the remaining useful life of the assets and compare that value to the carrying value of the assets. The amount of impairment, if any, is measured based on fair value, which is determined using projected discounted future operating cash flows. The cash flows that are used contain our best estimates, using appropriate and customary assumptions and projections at the time. If the cash flow estimates or the significant operating assumptions upon which they are based change in the future, we may be required to record additional impairment charges.

Goodwill

We assess goodwill for impairment annually in the fourth quarter and whenever events or circumstances indicate impairment may exist. This test includes first a qualitative assessment and then, if necessary, a quantitative assessment to determine if the fair value of a reporting unit is less than its carrying amount. Factors considered in the qualitative assessment include, but are not limited to, both macroeconomic conditions and entity-specific conditions. For the quantitative assessment, the reporting unit’s fair value is estimated using a discounted cash flow approach. Our reporting units that contain goodwill are our System One and In-Center operating segments. Assessing the impairment of goodwill requires us to make assumptions and judgments including the identification of reporting units and determination of the fair value of the net assets of our reporting units based on estimates of future cash flows and the selection of discount rates. Changes in these estimates and assumptions could materially affect the estimated fair values of reporting units and could result in a goodwill impairment charge in a future period. However, our annual impairment testing indicated no impairment based upon various factors including reporting unit valuations prepared using discounted cash flows, the positive performance of our reporting units, and positive industry and economic trends.

Accounting for Income Taxes

We periodically assess our income tax positions and record tax benefits for all years subject to examination based upon our evaluation of the facts, circumstances and information available at the reporting date. If our judgment as to the likely resolution of the position changes, if the matter is ultimately settled or if the statute of limitation expires, the effects of the change would be recognized in the period in which the change, resolution or expiration occurs.

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We conduct business globally and file income tax returns in the U.S. federal jurisdiction, various states and foreign jurisdictions. We evaluate the need for foreign income tax provisions or reserves based on our evaluation of inter-company transfer pricing. We evaluate the need for valuation allowances on our deferred tax assets based on positive and negative evidence about our ability to realize deferred tax attributes. We have accumulated significant losses since our inception in 1998 in the U.S. Utilization of the net operating losses may be subject to limitations and certain tax years in the respective tax jurisdictions remain open to examination.

Recent Accounting Pronouncements

A discussion of recent accounting pronouncements is included in Note 2 to the consolidated financial statements in this Annual Report.

Item 7A. Quantitative and Qualitative Disclosures About Market Risk

Interest Rate Risk

Our interest rate risk is currently limited to our investments. However, this risk is mitigated given our investment portfolio currently consists of treasury obligation money market funds. We manage our investment portfolio in accordance with our investment policy. The primary objectives of our investment policy are to preserve principal, maintain a high degree of liquidity to meet operating needs and obtain competitive returns subject to prevailing market conditions. Our investment policy specifies the credit quality standards for our investments and limits the amount of exposure from any single issue, issuer or type of investment.

Foreign Currency Exchange Risk

Our functional currency is the U.S. dollar and a majority of our revenues and expenses are denominated in U.S. dollars. However, we have manufacturing, service and distribution operations in foreign locations, namely Mexico, Germany, Italy and the United Kingdom. In addition, we purchase products for resale in the U.S. from foreign companies and have agreed to pay them in currencies other than the U.S. dollar, including the euro. Furthermore, certain revenues are denominated in other currencies, primarily the euro. As a result, we are potentially exposed to adverse as well as beneficial movements in foreign currency exchange rates. For example, a hypothetical 10% adverse change in exchange rates could have the net effect of reducing our operating profit by approximately $4.2 million.

We utilize natural hedges to minimize our transaction exposures. Also, certain of our long-term supply agreements include foreign exchange risk sharing at different exchange rate levels limiting our exposure to fluctuations in foreign exchange rates for our purchase commitment exposures. Finally, we enter into foreign exchange forward contracts on peso denominated expenses to further reduce our exposure to foreign currency exchange rate fluctuations from our foreign operations located in Mexico.

Our foreign exchange forward contracts are entered into with large financial institutions and have durations of up to twelve months. These contracts are designated as cash flow hedges and are carried on our balance sheet at fair value, with the effective portion of the contracts’ gains or losses included in cost of revenues in the same period as the related hedged item is recognized. As of December 31, 2014, the notional amount of our outstanding contracts that are designated as cash flow hedges was approximately $12.5 million. Based on our analysis, a hypothetical adverse foreign exchange rate movement of 10% against our contracts would have resulted in a net loss in fair value of these contracts of approximately $1.3 million.

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Item 8. Financial Statements and Supplementary Data

NXSTAGE MEDICAL, INC.

INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

Report of Independent Registered Public Accounting Firm	77
Consolidated Balance Sheets	78
Consolidated Statements of Comprehensive Loss	79
Consolidated Statements of Changes in Stockholders’ Equity	80
Consolidated Statements of Cash Flows	82
Notes to Consolidated Financial Statements	83

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REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Board of Directors and Shareholders of NxStage Medical, Inc.

We have audited the accompanying consolidated balance sheets of NxStage Medical, Inc. as of December 31, 2014 and 2013, and the related consolidated statements of comprehensive loss, changes in shareholders’ equity and cash flows for each of the three years in the period ended December 31, 2014. These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects, the consolidated financial position of NxStage Medical, Inc. at December 31, 2014 and 2013, and the consolidated results of its operations and its cash flows for each of the three years in the period ended December 31, 2014, in conformity with U.S. generally accepted accounting principles.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States), NxStage Medical, Inc.’s internal control over financial reporting as of December 31, 2014, based on criteria established in Internal Control-Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework) and our report dated February 26, 2015 expressed an unqualified opinion thereon.

/s/ Ernst & Young LLP

Boston, Massachusetts

February 26, 2015

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NXSTAGE MEDICAL, INC.

CONSOLIDATED BALANCE SHEETS

	December 31,
	2014			2013
	(In thousands, except share data)
ASSETS
Current assets:
Cash and cash equivalents	$	52,884		$	84,134
Accounts receivable, net		24,099			20,158
Inventory		45,401			37,801
Prepaid expenses and other current assets		6,767			4,027
Total current assets		129,151			146,120
Property and equipment, net		66,574			52,478
Field equipment, net		21,118			13,041
Deferred cost of revenues		34,039			34,730
Intangible assets, net		14,370			17,194
Goodwill		41,817			41,817
Other assets		2,657			1,582
Total assets	$	309,726		$	306,962
LIABILITIES AND STOCKHOLDERS’ EQUITY
Current liabilities:
Accounts payable	$	13,845		$	14,610
Accrued expenses		24,653			21,025
Current portion of long-term debt		93			102
Other current liabilities		6,165			1,870
Total current liabilities		44,756			37,607
Deferred revenues		52,943			53,277
Long-term debt		848			1,044
Other long-term liabilities		19,624			20,273
Total liabilities		118,171			112,201
Commitments and contingencies (Note 10)
Stockholders’ equity:
Undesignated preferred stock: par value $0.001, 5,000,000 shares authorized; no shares issued and outstanding as of December 31, 2014 and 2013		—			—
Common stock: par value $0.001, 100,000,000 shares authorized; 63,429,005 and 61,666,048 shares issued as of December 31, 2014 and 2013, respectively		63			61
Additional paid-in capital		593,073			567,468
Accumulated deficit		(387,488	)		(363,542	)
Accumulated other comprehensive (loss) income		(2,192	)		212
Treasury stock, at cost: 772,273 and 575,895 shares as of December 31, 2014 and 2013, respectively		(12,989	)		(9,963	)
Total NxStage Medical, Inc. stockholders’ equity		190,467			194,236
Noncontrolling interest		1,088			525
Total stockholders’ equity		191,555			194,761
Total liabilities and stockholders’ equity	$	309,726		$	306,962

See accompanying notes to these consolidated financial statements.

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NXSTAGE MEDICAL, INC.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS

	Years Ended December 31,
	2014			2013			2012
	(In thousands, except per share data)
Revenues	$	301,501		$	263,429		$	242,132
Cost of revenues		185,598			160,926			149,324
Gross profit		115,903			102,503			92,808
Operating expenses:
Selling and marketing		55,385			47,842			40,485
Research and development		22,635			18,887			17,111
Distribution		26,001			21,246			18,888
General and administrative		34,069			32,326			27,530
Total operating expenses		138,090			120,301			104,014
Loss from operations		(22,187	)		(17,798	)		(11,206	)
Other expense:
Interest expense		(863	)		(611	)		(2,766	)
Other expense, net		(10	)		(397	)		(148	)
		(873	)		(1,008	)		(2,914	)
Net loss before income taxes		(23,060	)		(18,806	)		(14,120	)
Provision for (benefit from) income taxes		1,253			(245	)		1,033
Net loss		(24,313	)		(18,561	)		(15,153	)
Less: Net loss attributable to noncontrolling interests		(367	)		—			—
Net loss attributable to stockholders of NxStage Medical, Inc.	$	(23,946	)	$	(18,561	)	$	(15,153	)
Net loss per share, basic and diluted	$	(0.39	)	$	(0.31	)	$	(0.26	)
Weighted-average shares outstanding, basic and diluted		61,700			60,261			57,890
Other comprehensive (loss) income, net of tax		(2,404	)		(258	)		538
Total comprehensive loss		(26,717	)		(18,819	)	$	(14,615	)
Less: Comprehensive loss attributable to noncontrolling interests		(367	)		—			—
Total comprehensive loss attributable to stockholders of NxStage Medical, Inc.	$	(26,350	)	$	(18,819	)	$	(14,615	)

See accompanying notes to these consolidated financial statements.

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NXSTAGE MEDICAL, INC

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY

	Common Stock				Additional Paid-In Capital			Accumulated Deficit			Accumulated Other Comprehensive Income (Loss)			Treasury Stock			Total NxStage Medical, Inc. Stockholders’ Equity			Noncontrolling Interest		Total Stockholders’ Equity
	Shares		Amount
	(In thousands, except share data)
Balance at December 31, 2011		56,167,090	$	56	$	489,542		$	(329,828	)	$	(68	)	$	(8,516	)	$	151,186		$	—	$	151,186
Net loss		—		—		—			(15,153	)		—			—			(15,153	)		—		(15,153	)
Adjustments to other comprehensive loss, net of tax		—		—		—			—			538			—			538			—		538
Issuance of common stock, net of issuance costs		2,456,246		2		45,074			—			—			(522	)		44,554			—		44,554
Exercise of stock options		913,066		1		6,344			—			—			(513	)		5,832			—		5,832
Shares issued under employee restricted stock plans		200,587		—		(1,173	)		—			—			—			(1,173	)		—		(1,173	)
Shares issued under employee bonus plans		47,533		—		878			—			—			—			878			—		878
Shares issued under employee stock purchase plan		56,691		—		731			—			—			—			731			—		731
Shares issued to Directors in lieu of cash		8,904		—		138			—			—			—			138			—		138
Stock-based compensation expense		—		—		10,060			—			—			—			10,060			—		10,060
Balance at December 31, 2012		59,850,117		59		551,594			(344,981	)		470			(9,551	)		197,591			—		197,591
Net loss		—		—		—			(18,561	)		—			—			(18,561	)		—		(18,561	)
Adjustments to other comprehensive loss, net of tax		—		—		—			—			(258	)		—			(258	)		—		(258	)
Exercise of stock options		662,767		1		4,666			—			—			(412	)		4,255			—		4,255
Exercise of warrants		874,921		1		892			—			—			—			893			—		893
Shares issued under employee restricted stock plans		105,573		—		(424	)		—			—			—			(424	)		—		(424	)
Shares issued under employee bonus plans		93,778		—		1,034			—			—			—			1,034			—		1,034
Shares issued under employee stock purchase plan		75,301		—		759			—			—			—			759			—		759
Shares issued to Directors in lieu of cash		3,591		—		42			—			—			—			42			—		42
Stock-based compensation expense		—		—		8,905			—			—			—			8,905			—		8,905
Contributions from noncontrolling interest		—		—		—			—			—			—			—			525		525
Balance at December 31, 2013		61,666,048	$	61	$	567,468		$	(363,542	)	$	212		$	(9,963	)	$	194,236		$	525	$	194,761

See accompanying notes to these consolidated financial statements.

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NXSTAGE MEDICAL, INC

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY

					Additional Paid-In Capital			Accumulated Deficit			Accumulated Other Comprehensive Income (Loss)			Treasury Stock			Total NxStage Medical, Inc. Stockholders’ Equity			Noncontrolling Interest			Total Stockholders’ Equity
	Common Stock
	Shares		Amount
	(In thousands, except share data)
Balance at December 31, 2013		61,666,048	$	61	$	567,468		$	(363,542	)	$	212		$	(9,963	)	$	194,236		$	525		$	194,761
Net loss		—		—		—			(23,946	)		—			—			(23,946	)		(367	)		(24,313	)
Adjustments to other comprehensive loss, net of tax		—		—		—			—			(2,404	)		—			(2,404	)		—			(2,404	)
Exercise of stock options		1,524,601		2		13,775			—			—			(3,026	)		10,751			—			10,751
Shares issued under employee restricted stock plans		166,127		—		(422	)		—			—			—			(422	)		—			(422	)
Shares issued under employee stock purchase plan		70,899		—		804			—			—			—			804			—			804
Shares issued to Directors in lieu of cash		1,330		—		18			—			—			—			18			—			18
Stock-based compensation expense		—		—		11,430			—			—			—			11,430			—			11,430
Contributions from noncontrolling interest		—		—		—			—			—			—			—			930			930
Balance at December 31, 2014		63,429,005	$	63	$	593,073		$	(387,488	)	$	(2,192	)	$	(12,989	)	$	190,467		$	1,088		$	191,555

See accompanying notes to these consolidated financial statements.

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NXSTAGE MEDICAL, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

	Years Ended December 31,
	2014			2013			2012
	(In thousands)
Cash flows from operating activities:
Net loss	$	(24,313	)	$	(18,561	)	$	(15,153	)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization		27,697			24,848			23,673
Stock-based compensation		12,881			8,638			11,403
Other		1,877			2,628			3,517
Changes in operating assets and liabilities:
Accounts receivable		(4,188	)		(1,095	)		(3,141	)
Inventory		(35,063	)		(20,076	)		(14,545	)
Prepaid expenses and other assets		(2,214	)		(484	)		(1,623	)
Accounts payable		(212	)		(2,233	)		839
Accrued expenses and other liabilities		4,235			1,081			5,263
Deferred revenues		(973	)		(4,887	)		(3,992	)
Net cash (used in) provided by operating activities		(20,273	)		(10,141	)		6,241
Cash flows from investing activities:
Cash paid for acquisition		—			(2,234	)		—
Purchases of property and equipment		(20,097	)		(16,246	)		(7,694	)
Net cash used in investing activities		(20,097	)		(18,480	)		(7,694	)
Cash flows from financing activities:
Proceeds from exercise of stock options and warrants and employee stock purchase plans		11,133			5,484			5,248
Investment by noncontrolling interest holder		930			525			—
Purchase of treasury stock		—			—			(522	)
Proceeds from loans and lines of credit		—			1,136			—
Repayments on loans and lines of credit		(98	)		(38	)		—
Payments on capital leases		(1,448	)		(1,352	)		—
Debt issuance costs		(1,056	)		—			—
Net cash provided by financing activities		9,461			5,755			4,726
Foreign exchange effect on cash and cash equivalents		(341	)		561			257
(Decrease) increase in cash and cash equivalents		(31,250	)		(22,305	)		3,530
Cash and cash equivalents, beginning of year		84,134			106,439			102,909
Cash and cash equivalents, end of year	$	52,884		$	84,134		$	106,439

See accompanying notes to these consolidated financial statements.

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NXSTAGE MEDICAL, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1. Nature of Operations

We are a medical device company that develops, manufactures and markets innovative products for the treatment of kidney failure, fluid overload and related blood treatments and procedures. Our primary product, the System One, was designed to satisfy an unmet clinical need for a system that can deliver the therapeutic flexibility and clinical benefits associated with traditional dialysis machines in a smaller, portable, easy-to-use form that can be used by healthcare professionals and trained lay users alike in a variety of settings, including patient homes, as well as more traditional care settings such as hospitals and dialysis centers. Given its design, the System One is particularly well-suited for home hemodialysis and a range of dialysis therapies including more frequent dialysis and nocturnal dialysis, which clinical literature suggests provides patients better clinical outcomes and improved quality of life. The System One is cleared or approved for commercial sale in the U.S., Canada and certain other markets, and is CE marked in the EU, for the treatment of acute and chronic kidney failure and fluid overload. The System One is cleared specifically by the U.S. Food and Drug Administration (FDA) for home hemodialysis and home nocturnal hemodialysis, as well as therapeutic plasma exchange in a clinical environment. The System One is also CE marked in the EU for home nocturnal hemodialysis. In February 2013, we received CE Mark approval and in April 2013 we received clearance from the FDA for the new high flow capabilities with the NxStage System One. We began selling the System One with this feature to both U.S. customers and international distributors in 2014. We also sell, through our Medisystems subsidiary, blood tubing sets and needles primarily to dialysis centers for the treatment of end-stage renal disease (ESRD). These products are cleared or approved for commercial sale in the U.S., Canada and certain other markets and are CE marked in the EU. We believe our largest market opportunity is for the System One used in the home dialysis market for the treatment of ESRD. We operate a small number of NxStage Kidney Care dialysis centers focused on supporting home therapy and providing flexible in-center options with NxStage technology as part of our market development activities to increase home therapy access. We continue to make significant investments in marketing, research and development, and these dialysis centers, all of which are intended to help us to further penetrate and expand the market for our products.

2. Summary of Significant Accounting Policies

Principles of Consolidation and Basis of Presentation

The accompanying consolidated financial statements include the accounts of NxStage Medical, Inc. and our wholly-owned and majority-owned subsidiaries. All material intercompany transactions and balances have been eliminated in consolidation.

Use of Estimates

The preparation of our consolidated financial statements in conformity with GAAP requires our management to make estimates and assumptions that affect reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Revenue Recognition

We recognize revenue from product sales and services when earned. Revenues are recognized when: (a) there is persuasive evidence of an arrangement, (b) the product has been shipped or services and supplies have been provided to the customer, (c) the sales price is fixed or determinable and (d) collection is reasonably assured.

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Certain agreements with distributors allow for product returns and credits. For shipment of product sold to distributors, revenue is recognized at the time of sale if a reasonable estimate of future returns or credit can be made. If a reasonable estimate of future returns or credit cannot be made, we recognize revenue using the “sell-through” method. Under the “sell-through” method, revenue and related costs of revenue is deferred until the final resale of such products to end customers.

In addition to contractually determined volume discounts, in many agreements we offer rebates based on sales to specific end customers and discounts for early payment. Rebates and discounts are recorded as a reduction of sales and trade accounts receivable, based on our best estimate of the amount of probable future rebate or discount on current sales.

We enter into multiple-element arrangements that may include a combination of equipment, related disposables and services. Revenue arrangements with multiple elements are divided into separate units of accounting if specified criteria are met, including whether the delivered element has stand-alone value to the customer, the consideration received is allocated among the separate units based on their respective selling price, and the applicable revenue recognition criteria are applied to each of the separate units.

We determine selling price using vendor specific objective evidence (“VSOE”), if it exists, otherwise third-party evidence of selling price is used. If neither VSOE nor third-party evidence of selling price exists for a unit of accounting, we use best estimated selling price (“BESP”). We generally expect that we will not be able to establish third-party evidence due to the nature of our products and the markets in which we compete, and, as such, we typically will determine selling price using VSOE or BESP.

We determine BESP for an individual element based on consideration of both market and Company-specific factors, including the selling price and profit margin for similar products, the cost to produce the deliverable and the anticipated margin on that deliverable and the characteristics of the varying markets in which the deliverable is sold.

System One Segment

We derive revenue in the home market from the sales of hemodialysis therapy to customers in which the customer either purchases or rents the System One and/or PureFlow SL hardware and purchases a specified number of disposable products and service.

For customers that purchase the System One and PureFlow SL hardware, in the U.S. home market, due to the depot service model whereby equipment requiring service is picked up and a replacement device is shipped to the site of care, we recognize fees received from equipment sale as revenue on a straight-line basis over the expected term of our remaining service obligation and direct costs relating to the delivered equipment are deferred and amortized over the same expected period as the related revenue. Disposable products revenue is recognized on a monthly basis upon delivery.

Under the rental arrangements, revenue is recognized on a monthly basis in accordance with agreed upon contract terms and pursuant to binding customer purchase orders and fixed payment terms.

Our sales arrangements with our international distributors are structured as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms.

In the critical care market, we structure sales of the System One and disposable products as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Certain of

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these arrangements provide for training, technical support and extended warranty services to our customers. We recognize training and technical support revenue when the related services are performed. In the case of extended warranty, the service revenue is recognized ratably over the extended warranty period.

In-Center Segment

Our In-Center segment sales are structured as direct product sales primarily through distributors, and we have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Some of our distribution contracts for the In-Center segment contain minimum volume commitments with negotiated pricing discounts at different volume tiers. Each agreement may be canceled upon a material breach, subject to certain curing rights, and in many instances minimum volume commitments can be reduced or eliminated upon certain events.

Services Segment

Revenues in our Services segment are derived from dialysis care services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

Revenues are recognized based on a customary fee schedule, net of estimated contractual allowances to reflect the estimated amounts to be received from the payor. Revenues are recognized in the period in which services are provided when we have the ability to reasonably estimate amounts ultimately collectible from the payor. In instances where we do not have the ability to reasonably estimate amounts ultimately collectible, as is often the case with non-contracted commercial health plans and amounts due from patients (including co-pay and deductible amounts), revenue is recognized in the period in which cash is received.

Foreign Currency Translation and Transactions

Assets and liabilities of our foreign operations are translated into U.S. dollars at current exchange rates, and income and expense items are translated at average rates of exchange prevailing during the year. Foreign exchange gains and (losses) on intercompany loans considered permanent investments are recorded in other comprehensive loss. Gains and (losses) realized from transactions denominated in foreign currencies, including intercompany balances not considered permanent investments, are included in the consolidated statements of comprehensive loss within other (expense) income, net.

Cash and Cash Equivalents

We consider all highly-liquid investments purchased with original maturities of 90 days or less to be cash equivalents. Cash equivalents include amounts invested in treasury obligation money market funds. Cash equivalents are stated at cost plus accrued interest, which approximates market value.

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk consist principally of cash equivalents, derivatives and accounts receivable. To mitigate such risk, with respect to cash and cash equivalents, we place our cash in bank deposit accounts with financial institutions that have investment grade ratings and capital ratios exceeding minimum Federal Reserve Adequacy Guidelines and in treasury obligation money market funds. To mitigate concentration of credit risk with respect to derivatives we enter into transactions with highly-rated financial institutions and frequently monitor the credit worthiness of our counterparties.

Concentration of credit risk with respect to accounts receivable is primarily limited to certain customers to whom we make substantial sales. Two customers represented 18% and 16% of accounts receivable at December 31, 2014 and one customer represented 19% of accounts receivable at December 31, 2013. To reduce risk, we routinely assess the financial strength of our customers and closely monitor their amounts due and, as a

85

result of our assessment, believe that our accounts receivable credit risk exposure is limited. Historically, we have not experienced any significant credit losses related to an individual customer or group of customers in any particular market or geographic area. We maintain an allowance for doubtful accounts based on an analysis of historical losses from uncollectible accounts, aging of unpaid accounts receivable balances and risks identified for specific customers who may not be able to make required payments. Provisions for the allowance for doubtful accounts are recorded in general and administrative expenses in the accompanying consolidated statements of comprehensive loss.

Activity related to allowance for doubtful accounts consisted of the following (in thousands):

Year Ended	Balance at Beginning of Year		Provision (Recoveries)		Write-offs			Balance at End of Year
December 31, 2014	$	321	$	219	$	(115	)	$	425
December 31, 2013	$	424	$	47	$	(150	)	$	321
December 31, 2012	$	510	$	—	$	(86	)	$	424

We use and are dependent upon a number of single source suppliers of raw materials, components, finished goods and sterilization services. We are dependent on the ability of our suppliers to provide products on a timely basis and on favorable pricing terms. The loss of certain principal suppliers or a significant reduction in product availability from principal suppliers would have a material adverse effect on us, at least in the near term. We believe that our relationships with our suppliers are satisfactory.

Fair Value Measures

Certain financial and non financial assets and liabilities recorded at fair value have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standard. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable such as quoted prices, interest rates and yield curves for similar instruments and model-derived valuations whose inputs are observable. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability.

Derivative Instruments and Hedging

Derivative instruments, namely our foreign exchange forward contracts, are recognized on the balance sheet at fair value at the balance sheet date. Changes in the fair value of derivatives that are designated and highly effective as cash flow hedges are deferred in accumulated other comprehensive income (loss) and subsequently recognized in cost of revenues in the same period the hedged items are recognized. The ineffective portion of derivative instruments designated as cash flow hedges, are recorded in other income (expense), net. If the underlying forecasted transaction does not occur, or it becomes probable that it will not occur, the gains and losses on the related derivative instrument are recognized in earnings and any related gains and losses recorded in other comprehensive income (loss) are reclassified into earnings.

Inventory

Inventory is stated at the lower of cost, determined using the first-in first-out method (FIFO), or market (net realizable value). We record a provision for any excess or obsolete inventory when warranted based on remaining shelf-life and estimated future demand. We also review our inventory value to determine if it reflects the lower of cost or market based on factors such as inventory items sold at negative gross margins and purchase commitments.

Property and Equipment and Field Equipment

Property and equipment and field equipment are recorded at cost less accumulated depreciation. Depreciation is provided over the estimated useful lives of the related assets using the straight-line method for

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financial statement purposes. The estimated useful life of our assets are periodically reviewed for reasonableness. Changes in useful lives are accounted for prospectively. Repairs and maintenance are expensed as incurred. When property and equipment are retired, sold or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in operations. When field equipment is sold, the asset’s carrying amount and related accumulated depreciation is removed from the accounts and any gain or loss is deferred and recognized in operations on a straight-line basis over the same period as the related revenues.

We capitalize certain costs, including internal payroll and external direct project costs, incurred in connection with developing or obtaining software designated for internal use. These costs are included in property and equipment and are amortized over the estimated useful lives of the related software.

Construction-in-process is stated at cost, which includes the cost of construction and other direct costs attributable to the construction. No provision for depreciation is made on construction-in-process until such time as the relevant assets are completed and put into use. Construction-in-process at December 31, 2014 and 2013 primarily represents the costs of building, machinery, equipment under installation and software and computer costs.

Field equipment consists of equipment being utilized under disposable-based rental agreements as well as “service pool” equipment. Service pool equipment is equipment owned and maintained by us that are swapped for equipment that need repairs or maintenance by us while being rented or owned by a customer. We record a provision for any excess, lost or damaged equipment when warranted based on an assessment of the equipment in the service pool. Write-downs for equipment are included in distribution expenses.

The estimated useful lives of property and equipment and field equipment are as follows:

	Estimated Useful Life
Buildings	30 years
Manufacturing equipment and tooling	3 to 12 years
Leasehold improvements	Lesser of the lease term (including any renewal periods if appropriate) or estimated useful life of the asset
Computer and office equipment	3 to 5 years
Molds	5 to 7 years
Furniture	5 to 7 years
Field equipment	5 to 7 years

Intangibles and Other Long-Lived Assets

Intangible assets are carried at cost less accumulated amortization. For assets with determinable useful lives, amortization is computed using the straight-line method over the estimated economic lives of the respective intangible assets, ranging from eight to fourteen years. Long-lived assets, including intangible assets, are tested for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. The amount of impairment, if any, is measured based on fair value, which is determined using estimated discounted cash flows to be generated from such assets or group of assets. During 2014, 2013 and 2012, no such impairment was recognized. Assets to be disposed of are reported at the lower of the carrying amount or fair value less selling costs.

Goodwill

Goodwill represents the excess of the cost of an acquired business over the fair value of the related net assets at the date of acquisition. We test goodwill at least annually for impairment, or more frequently when events or changes in circumstances indicate that the goodwill might be impaired. This impairment test is

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performed annually during the fourth quarter. This test includes first a qualitative assessment and then, if necessary, a quantitative assessment to determine if the fair value of a reporting unit is less than its carrying amount. Factors considered in the qualitative assessment include, but are not limited to, both macroeconomic conditions and entity-specific conditions. For the quantitative assessment the reporting unit’s fair value is estimated using a discounted cash flow or other fair value measurement. Our reporting units with goodwill are our System One and In-center operating segments. During both 2014 and 2012, we utilized the qualitative assessment and concluded that it was more likely than not that the fair value of our reporting units was greater than their carrying value. During 2013, we utilized the quantitative assessment and concluded the fair value of the reporting units exceeds their carrying value, indicating that goodwill was not impaired. We estimated the fair value of our reporting units using a discounted cash flow approach which involves significant judgment with respect to future revenue growth, operating income, capital expenditures, changes in working capital use and the selection of a discount rate.

Stock-Based Compensation

Stock-based compensation expense is estimated as of the grant date based on the fair value of the award. We use the Black-Scholes option pricing model to estimate the fair value of stock options and quoted market prices of our common stock to estimate fair value of restricted stock. The expected term is estimated based on the contractual term of each grant and takes into account the historical experience and relevant factors concerning expected exercise and termination behavior of participants. The risk free interest rate for each grant is equal to the U.S. Treasury rate in effect at the time of grant for instruments with an expected life similar to the expected term. The stock volatility assumption is based solely on our historical volatility over the expected term of the award. The dividend yield of zero is based upon the fact that we have not historically granted cash dividends, and do not expect to issue dividends in the foreseeable future.

We recognize stock-based compensation expense over the requisite service period, which generally equals the vesting period, net of forfeitures. Forfeiture rates are estimated based on historical pre-vesting forfeiture history and are updated on a quarterly basis to reflect actual forfeitures of unvested awards and other known events. For awards that vest based on employment, we recognize the associated compensation expense on a straight-line basis. For performance based awards, we recognize expense using the graded vesting methodology based on the number of shares expected to vest. Compensation expense associated with these performance based awards is adjusted quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date the results are determined.

Warranty Costs

We accrue estimated costs that we may incur under our product warranty programs at the time the product revenue is recognized, based on contractual rights and historical experience. Warranty expense is included in cost of revenues in the consolidated statements of comprehensive loss. The following is a rollforward of our warranty accrual (in thousands):

Year Ended	Balance at Beginning of Year		Provision		Usage			Balance at End of Year
December 31, 2014	$	297	$	441	$	(451	)	$	287
December 31, 2013	$	324	$	412	$	(439	)	$	297
December 31, 2012	$	380	$	540	$	(596	)	$	324

Distribution Expenses

Distribution expenses are charged to operations as incurred and consist of costs incurred in shipping product to and from customers and the cost of any equipment lost or damaged in the distribution process. Shipping and handling costs billed to customers are included in revenues.

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Research and Development Costs

Research and development costs are charged to operations as incurred.

Income Taxes

We record the tax effect of transactions when such transactions are recorded in our consolidated statement of comprehensive loss. We record a deferred tax asset or liability based on the difference between the financial statement and tax basis of assets and liabilities, as measured by the enacted tax rates. Our provision for income taxes represents the amount of taxes currently payable, if any, plus the change in the amount of net deferred tax assets or liabilities. A valuation allowance is provided against net deferred tax assets if recoverability is uncertain on a more likely than not basis.

We periodically assess our exposures related to our provisions for income taxes and accrue for contingencies that may result in potential tax obligations. For those positions where it is more likely than not that a tax benefit will be sustained, we record the largest amount of tax benefit with a greater than 50 percent likelihood of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the financial statements. We recognize interest and penalties for uncertain tax positions in income tax expense.

We conduct business globally and file income tax returns in the U.S. federal jurisdiction, various states and foreign jurisdictions. We have accumulated significant losses since our inception in 1998. Utilization of the net operating losses may be subject to limitations and certain tax years in the respective tax jurisdictions remain open to examination.

Subsequent Events

Events occurring subsequent to December 31, 2014 have been evaluated for potential recognition or disclosure in the consolidated financial statements.

Recent Accounting Pronouncements

Effective January 1, 2014, we adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists,” which impacts the presentation of unrecognized tax benefits on the statement of financial position. As a result, unrecognized tax benefits are presented as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. To the extent the tax benefit is not available at the reporting date under the governing tax law or if we do not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit is presented as a liability and not combined with deferred tax assets. The adoption of this standard did not impact our condensed consolidated financial statements, as our practice was consistent with this standard prior to its effective date.

In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers,” which provides guidance for revenue recognition. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. Early application is not permitted. We are currently assessing the potential impact the adoption of this standard will have on our financial statements.

In August 2014, the FASB issued ASU No. 2014-15, “Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern” (“ASU 2014-15”), which expands upon principles that are currently in U.S.

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auditing standards by providing guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and by providing related footnote disclosure requirements. The new guidance is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early adoption is permitted. We are currently evaluating the impact of this update but it is not expected to have a material impact on our financial statement disclosures.

3. Inventory

Inventory includes material, labor and overhead. The components of inventory are as follows (in thousands):

	December 31,
	2014		2013
Purchased components	$	19,238	$	15,946
Work in process		9,981		10,762
Finished goods		16,182		11,093
	$	45,401	$	37,801

4. Property and Equipment, Field Equipment and Deferred Cost of Revenues

Property and Equipment, net

The components of property and equipment, net are as follows (in thousands):

	December 31,
	2014			2013
Manufacturing equipment and tooling	$	34,621		$	24,963
Leasehold improvements		18,485			11,883
Computer and office equipment		8,935			4,132
Molds		5,377			3,817
Furniture		2,410			1,712
Buildings		8,907			10,005
Land		1,110			1,258
Construction-in-process		14,609			16,500
		94,454			74,270
Less accumulated depreciation		(27,880	)		(21,792	)
Property and equipment, net	$	66,574		$	52,478

Depreciation expense, including amortization of capital leases, for property and equipment was $7.1 million, $4.7 million and $3.7 million during 2014, 2013 and 2012, respectively.

Included in construction-in-process as of December 31, 2013 was $4.5 million of capitalized computer development costs. There were no such costs included in construction-in-process at December 31, 2014. Capitalized computer development costs, net was $3.6 million at December 31, 2014 and we recognized amortization expense of $0.9 million during 2014.

Our property and equipment includes the following amounts for assets subject to capital leases (amounts in thousands):

	December 31, 2014
Manufacturing facility in Germany	$	22,750
Other assets subject to capital leases		2,438
Less accumulated depreciation		(2,905	)
Assets subject to capital leases, net	$	22,283

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Manufacturing Facility in Germany

Pursuant to our Dialyzer Production Agreement entered into in May 2009 with Asahi we agreed to oversee construction of a new manufacturing facility in Germany. Asahi funded construction costs of the facility, including land, building and equipment; however, given our involvement during construction we were considered the owner of the facility for accounting purposes and therefore, as required, we recorded the cost of the new facility within property and equipment on our consolidated balance sheet along with a corresponding liability within other long-term liabilities for the construction cost funded by Asahi.

Pursuant to the Dialyzer Production Agreement, we agreed to operate the facility and manufacture dialyzers for our own use and for sale to Asahi under a manufacturing agreement during the initial term of the agreement through June 2021 and thereafter, unless either party provides notice of its intent not to renew. Asahi agreed to pay us cost including material, labor and overhead (but excluding depreciation on the new facility), plus applicable statutory value added or turnover tax established or required by law for each dialyzer manufactured by us for Asahi. We are required to pay Asahi a fixed amount per dialyzer manufactured for our own use in the facility, with such payments capped at fifty percent of the cost of the facility paid by Asahi. If the agreement is terminated subsequent to completion of construction by us, Asahi has the option to require us to purchase the facility from them or if the agreement is terminated by Asahi, we have the option to purchase the facility from them. In either case the purchase price is equal to one hundred percent of the then net book value of the facility, as calculated in accordance with GAAP.

In December 2012 construction of the facility was completed, at which time the asset was placed in service. Given our continued involvement in the facility, we were precluded from derecognizing the cost of the facility or the corresponding liability. Therefore, the facility asset, including building and equipment, continued to be recorded within property and equipment, net, on our consolidated balance sheet and depreciated on a straight-line basis over its estimated useful life. The corresponding liability has been divided into two separate components, including a capital lease obligation and deferred revenue, based on their relative fair values at December 2012.

In December 2014, construction of an additional production line within the facility was completed, at which time additional assets were placed into service at a total cost of $6.4 million. Consistent with the facility completed in December 2012, we were precluded from derecognizing the cost of the additional production line or the corresponding liability. Therefore, the asset is being recorded within property and equipment, net, on our consolidated balance sheet and depreciated on a straight-line basis over its estimated useful life. The corresponding liability has been divided into two separate components, including a capital lease obligation and deferred revenue, based on their relative fair values at December 2014 of $3.5 million and $2.9 million, respectively.

The fair value of the capital lease obligation was determined based on the present value of the financing payments due plus the residual value guarantee. The key assumptions used to determine the fair value of this liability included our incremental borrowing rate, the fixed amount per dialyzer payment due to Asahi totaling fifty percent of the cost of the asset paid by Asahi, and the estimated residual value of the assets at the end of the estimated lease term all of which we determined to be Level 3 inputs within the fair value hierarchy. The capital lease obligation has been classified within other long-term liabilities within our consolidated balances sheet with the amount expected to be paid within one year classified within other current liabilities. The capital lease obligation is decreased by payments made to Asahi for dialyzers manufactured for our own use and increased by interest expense.

The fair value of the deferred revenue was determined using cost plus a reasonable margin for contract manufacturing in Germany, Level 3 inputs within the fair value hierarchy. The deferred revenue is recognized in revenues on a straight-line basis over the expected term of the Dialyzer Production Agreement.

The capital lease obligation and deferred revenue balances are $12.7 million and $8.2 million, respectively, at December 31, 2014.

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Field Equipment, net

The components of field equipment, net are as follows (in thousands):

	December 31,
	2014			2013
Field equipment	$	61,132		$	49,695
Less accumulated depreciation		(40,014	)		(36,654	)
Field equipment, net	$	21,118		$	13,041

Depreciation expense for field equipment, which is recorded in costs of revenues in the consolidated statements of comprehensive loss, was $4.2 million, $4.0 million and $3.7 million during 2014, 2013 and 2012, respectively.

Deferred Costs of Revenues

Amortization expense of direct costs relating to deferred equipment revenues was $13.5 million, $13.3 million and $13.5 million during 2014, 2013 and 2012, respectively.

5. Intangible Assets

The components of intangible assets, net are as follows (in thousands):

	December 31, 2014					December 31, 2013					Estimated Useful Life
	Cost		Accumulated Amortization			Cost		Accumulated Amortization
Bloodline, needle and other patented and unpatented technology	$	6,200	$	(5,619	)	$	6,200	$	(4,844	)		8 years
Trade names		2,300		(1,191	)		2,300		(1,026	)		14 years
Customer relationships		26,175		(13,495	)		26,185		(11,621	)		10/14 years
Intangible assets, net	$	34,675	$	(20,305	)	$	34,685	$	(17,491	)

We recognized amortization expense of $2.8 million during each of 2014, 2013 and 2012.

The estimated future aggregated amortization expense for intangible assets as of December 31, 2014 is as follows (in thousands):

2015	$	2,621
2016		2,040
2017		2,040
2018		2,040
2019		2,040
Thereafter		3,589
	$	14,370

6. Net Loss per Share

Basic net loss per share is computed by dividing loss available to NxStage Medical, Inc. common stockholders (the numerator) by the weighted-average number of common shares outstanding (the denominator) for the period. The computation of diluted loss per share is similar to basic loss per share, except that the denominator is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued.

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The following potential common stock equivalents, as calculated using the treasury stock method, were not included in the computation of diluted net loss per share as their effect would have been anti-dilutive due to the net loss incurred (in thousands):

	Years Ended December 31,
	2014		2013		2012
Options to purchase common stock		876		1,013		1,602
Unvested restricted stock		236		152		196
Warrants to purchase common stock		—		—		921
Total		1,112		1,165		2,719

7. Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities

The components of accrued expenses are as follows (in thousands):

	December 31,
	2014		2013
Payroll, compensation and related benefits	$	12,346	$	9,041
Distribution expenses		3,069		2,762
General and administrative expenses		3,075		2,207
Audit, legal, and consulting fees		1,394		2,725
Other		4,769		4,290
Total	$	24,653	$	21,025

The components of other current liabilities are as follows (in thousands):

	December 31,
	2014		2013
Deferred revenue, current portion	$	2,195	$	—
Capital lease obligations		2,246		1,471
Other		1,724		399
Total	$	6,165	$	1,870

The components of other long term liabilities are as follows (in thousands):

	December 31,
	2014		2013
Capital lease obligations	$	11,876	$	14,133
Lease incentive obligations		4,569		3,589
Benefit plan obligations		1,745		1,770
Other		1,434		781
Total	$	19,624	$	20,273

8. Debt and Capital Lease Obligations

Manufacturing Facility in Italy

We entered into two euro denominated mortgages collateralized by a manufacturing facility in Italy that we acquired in May 2013. The first mortgage is in the principal amount of $0.6 million, subject to an annual interest rate of 6.0%, and payable quarterly over a 10 year period. The second mortgage is in the principal amount of $0.5 million, subject to an annual interest rate of 2.0%, and payable biannually over a 10 year period.

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Loan and Security Agreements

We had a loan and security agreement with Silicon Valley Bank, or SVB, that provided for a $15.0 million revolving line of credit. This agreement matured as of March 31, 2014.

On June 10, 2014, we entered into a new revolving line of credit with General Electric Capital Corporation, or GECC, and SVB that allows for borrowings up to $35 million. Availability of credit is subject to a borrowing base that is calculated with reference to certain of our accounts receivable, inventory and equipment, and adjustments to such borrowing base are at the discretion of the lenders. The new revolving line of credit is secured by substantially all of our assets and expires in June 2019. Borrowings bear interest at an annual rate equal to (1) a LIBOR rate plus 2.5% or (2) a base rate plus 1.5%, where the base rate is the highest of (a) the Prime Rate, (b) the Federal Funds Rate plus 0.5% and (c) a LIBOR rate plus 1%, at our election. The new revolving credit facility requires us to comply with certain covenants while borrowings are outstanding and contains events of default customary for a transaction of this type.

As of December 31, 2014, there were no outstanding borrowings under the $35 million revolving line of credit, we were in compliance with all applicable covenants and, subject to the lenders’ adjustments described above, we had approximately $28 million of credit commitment available for borrowing.

Capital Lease Obligations

Our capital lease obligations consist of certain property and equipment financed through capital leases and our capital lease obligation due to Asahi related to the manufacturing facility in Germany. Approximate future minimum payments under our capital leases as of December 31, 2014 are as follows (in thousands):

2015	$	2,326
2016		2,312
2017		1,925
2018		1,506
2019		851
Thereafter (1)		9,065
Total minimum lease payments		17,985
Less amount representing interest		(3,863	)
Present value of future minimum lease payments	$	14,122

(1) Amount includes $6.6 million representing the estimated residual value of the manufacturing facility in Germany at the end of the estimated lease term, which only becomes due and payable at Asahi’s option if we terminate our agreement with Asahi.

9. Business Segment and Geographic Information

With our continued investment in our NxStage Kidney Care dialysis centers, effective with the first quarter of 2014, it was determined that the operations of NxStage Kidney Care should be presented separately. Prior to 2014, its operations were included within the Other category. We now have three reportable business segments: System One, In-Center, and Services. The operating results of NxStage Kidney Care are included in our Services segment. We distribute our products in three markets: home, critical care and in-center. Prior period information has been updated to conform with the current presentation.

Our System One segment includes revenues from the sale and rental of the System One and PureFlow SL dialysate preparation equipment and the sale of disposable products in the home and critical care markets. The home market is devoted to the treatment of ESRD patients in the home or a home-like setting, while the critical care market is devoted to the treatment of hospital-based patients with acute kidney failure or fluid overload.

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Some of our largest customers in the home market provide outsourced renal dialysis services to some of our customers in the critical care market. Sales of product to both markets are made primarily through dedicated sales forces and distributed directly to the customer, or the patient, with certain products sold through distributors. The results of our international business are included in the System One segment.

Our In-Center segment includes revenues from the sale of blood tubing sets and needles for hemodialysis primarily for the treatment of ESRD patients at dialysis centers and needles for apheresis. Nearly all In-Center products are sold through national distributors.

Our Services segment includes revenues from dialysis services provided to patients at our NxStage Kidney Care dialysis centers.

The remainder of our operations and financial information, included within the Other category, relates primarily to the manufacturing of dialyzers for sale to Asahi and research and development and general and administrative expenses that are excluded from the segment operating performance measures.

The accounting policies of our reportable segments are the same as those described in Note 2. Our chief operating decision maker allocates resources to our business segments and assesses segment performance based on segment profit (loss), which consists of revenues less cost of revenues, selling and marketing and distribution expenses.

The following summarizes the operating performance of our reportable segments (in thousands):

	System One		In-Center		Other			Services			Intersegment Revenue Elimination			Total
Year Ended December 31, 2014
Revenues from external customers	$	212,585	$	78,885	$	8,282		$	1,749		$	—		$	301,501
Intersegment Revenues		846		—		—			—			(846	)		—
Revenues		213,431		78,885		8,282			1,749			(846	)		301,501
Segment profit (loss)		36,802		12,815		(56,878	)		(14,926	)		—			(22,187	)
Depreciation and amortization		20,205		1,608		4,829			1,055			—			27,697
Segment assets		127,212		29,613		136,041			16,860			—			309,726
Year Ended December 31, 2013
Revenues from external customers	$	176,756	$	81,852	$	4,469		$	352		$	—		$	263,429
Intersegment Revenues		—		—		—			—			—			—
Revenues		176,756		81,852		4,469			352			—			263,429
Segment profit (loss)		24,036		16,447		(52,591	)		(5,690	)		—			(17,798	)
Depreciation and amortization		18,041		1,389		5,283			135			—			24,848
Segment assets		110,124		26,414		166,151			4,273			—			306,962
Year Ended December 31, 2012
Revenues from external customers	$	163,129	$	76,927	$	2,076		$	—		$	—		$	242,132
Intersegment Revenues		—		—		—			—			—			—
Revenues		163,129		76,927		2,076			—			—			242,132
Segment profit (loss)		24,349		11,051		(45,388	)		(1,218	)		—			(11,206	)
Depreciation and amortization		18,245		1,461		3,967			—			—			23,673
Segment assets		80,041		20,582		211,326			—			—			311,949

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The following table presents a reconciliation of the total segment assets to total assets (in thousands):

	December 31,
	2014		2013
Total segment assets	$	173,685	$	140,811
Corporate assets:
Cash and cash equivalents		52,884		84,134
Accounts Receivable, net		277		397
Property and equipment, net		17,269		17,000
Intangible assets, net		14,370		17,194
Goodwill		41,817		41,817
Prepaid and other assets		9,424		5,609
Total assets	$	309,726	$	306,962

Long-lived tangible assets consist of property and equipment, net and field equipment, net. The following table presents total long-lived tangible assets by geographic area (in thousands):

	December 31,
	2014		2013		2012
United States	$	45,501	$	26,082	$	20,967
Mexico		12,689		10,578		3,949
Other Americas		482		94		—
Total Americas		58,672		36,754		24,916
Germany		21,246		20,235		17,058
Other Europe		7,774		8,530		4,447
Total Europe		29,020		28,765		21,505
Total	$	87,692	$	65,519	$	46,421

Substantially all of our revenues are derived from the sale of the System One and related products, which cannot be used with any other dialysis system, and from needles and blood tubing sets to customers located in the U.S.

The following table summarizes the number of customers who individually make up greater than ten percent of total revenues:

	Years Ended December 31,
	2014			2013			2012
DaVita		21	%		21	%		21	%
Fresenius		16	%		14	%		11	%
Gambro		9	%		12	%		12	%
Schein		8	%		10	%		11	%

Sales to DaVita HealthCare Partners Inc. (DaVita) and Fresenius Medical Care (Fresenius) are in the System One segment. Sales to Gambro AB and Henry Schein, Inc. (Schein) are in the In-Center segment. All of Gambro’s sales of our products are to DaVita. A portion of Schein’s sales of our products are to DaVita.

10. Commitments and Contingencies

Purchase Commitments

We have agreements with certain of our suppliers, primarily for the purchase of certain System One components and fluids along with needles for our In-Center segment that include minimum purchase commitments. As of December 31, 2014, we had a total of $62.3 million in minimum purchase commitments under these agreements over the next one to five years.

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Operating Leases

Our operating leases relate to our corporate headquarters and NxStage Kidney Care facilities, as well as our foreign leased manufacturing facilities in Mexico, Germany and Italy.

Our corporate headquarters lease has an initial term of eleven years through mid-2023 with an early termination provision after seven years, subject to certain terms and conditions, with two 5-year options to extend beyond the initial term on substantially the same terms and at rent equal to ninety-five percent of the then fair market value. The lease included a tenant improvement allowance of $4.3 million.

Our NxStage Kidney Care facility lease agreements have initial lease terms through 2018 to 2022, contain renewal options ranging from five to ten years at the fair rental value at the time of renewal. The leases are generally subject to periodic consumer price index increases or contain fixed escalation clauses and include tenant improvement allowances ranging from $0.1million to $0.3 million per facility.

Our foreign leased manufacturing facilities are subject to lease agreements with termination dates through December 2015 to 2018 and contain renewal options at the fair rental value at the time of renewal.

Our lease agreements contain certain provisions that require us to pay executory costs such as real estate taxes, operating expenses and common utilities. Rent expense is recorded on a straight-line basis over the lease term. Tenant improvement allowances are recorded as a deferred rent obligation and amortized to rent expense over the term of the lease.

Rent expense under our operating leases was $3.8 million during 2014, $2.2 million during 2013 and $2.2 million during 2012.

The future minimum rental payments as of December 31, 2014 under our operating leases are as follows (in thousands):

2015	$	4,412
2016		4,390
2017		4,244
2018		4,369
2019		3,535
Thereafter		8,523
	$	29,473

Contingencies

A civil complaint was filed against us on February 28, 2012 by Gambro Renal Products, Inc., or Gambro. The complaint alleged that we made false and misleading statements about our and Gambro’s allegedly competing products in the critical care market in commercial and promotional activities. The complaint also alleged that we wrongfully interfered with contractual and advantageous relationships of Gambro in its critical care business.

Effective January 2, 2014, we and Gambro agreed to a settlement of this litigation without any admission of wrongdoing or liability. The settlement required us to pay a one-time cash payment to Gambro which was primarily offset by reimbursement from our insurance company. At the same time, we entered into a patent cross-license agreement and a distribution agreement amendment that amended the length and other terms of the agreement between us and Gambro. We recorded the settlement, reimbursement and consideration within general and administrative expense on the consolidated statements of comprehensive loss.

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11. Income Taxes

The following is a summary of income (loss) before income taxes by geography (in thousands):

	Years Ended December 31,
	2014			2013			2012
U.S.	$	(24,315	)	$	(20,613	)	$	(16,026	)
Foreign		1,255			1,807			1,906
Total	$	(23,060	)	$	(18,806	)	$	(14,120	)

The components of the provision for (benefit from) income taxes are as follows (in thousands):

	Years Ended December 31,
	2014			2013			2012
Current:
U.S. - State	$	57		$	47		$	52
Foreign		1,278			(76	)		1,357
Total Current		1,335			(29	)		1,409
Deferred:
Foreign		(82	)		(216	)		(376	)
Total Deferred		(82	)		(216	)		(376	)
Total Provision (Benefit)	$	1,253		$	(245	)	$	1,033

We recognized a provision for income taxes of $1.3 million during 2014, a benefit from income taxes of $0.2 million during 2013 and a provision for income taxes of $1.0 million during 2012. We recorded income tax expense during 2014, 2013 and 2012 for certain profitable foreign subsidiaries. The net benefit from income taxes recorded during 2013 includes the favorable conclusion of a foreign income tax audit which resulted in the recognition of a $1.2 million income tax benefit and a gain related to a foreign legislative change.

A reconciliation of the U.S. federal statutory tax rate to the effective tax rate is as follows:

	Years Ended December 31,
	2014			2013			2012
Federal statutory rate		34.0	%		34.0	%		34.0	%
Stock compensation		2.0	%		(2.5	)%		(5.6	)%
State income tax, net of federal tax benefit		1.9	%		3.2	%		2.0	%
U.S. research credits		4.1	%		11.7	%		3.3	%
Foreign income inclusion in the U.S.		(2.8	)%		(6.7	)%		(3.1	)%
Valuation allowance		(39.7	)%		(40.2	)%		(31.4	)%
Change in tax reserves		—	%		4.0	%		(5.6	)%
Other, net		(4.9	)%		(2.2	)%		(0.9	)%
Effective tax rate		(5.4	)%		1.3	%		(7.3	)%

The 2013 effective tax rate included a $1.2 million income tax benefit from the favorable conclusion of a foreign income tax audit.

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Deferred income tax assets and liabilities reflect the tax effects of differences in the recognition of income and expense items for tax and financial reporting purposes. Deferred tax assets (liabilities), the majority of which are non-current, are made up of the following (in thousands):

	December 31,
	2014			2013
Deferred tax assets:
Net operating loss carryforwards	$	114,131		$	108,772
Tax credits		10,078			9,464
Stock-based compensation		6,259			5,713
Capitalized research and development		3,120			3,677
Financing liabilities		6,281			5,007
Other		6,092			2,199
Total deferred tax assets		145,961			134,832
Deferred tax liabilities:
Fixed assets		(7,719	)		(5,079	)
Intangible assets		(5,326	)		(6,509	)
Other		(608	)		—
Total deferred tax liabilities		(13,653	)		(11,588	)
Net deferred tax assets before valuation allowance		132,308			123,244
Less valuation allowance		(131,453	)		(122,353	)
Net deferred tax assets	$	855		$	891

As of December 31, 2014, we had U.S. federal and state net operating loss carryforwards of approximately $366 million and $187 million, respectively, available to offset future taxable income. A portion of the federal net operating loss, $54.2 million, and state net operating loss, $27.7 million, is attributable to excess tax deductions related to stock-based compensation. We will realize the benefit of these excess tax deductions through increases in shareholder’s equity in future periods when and if the losses are utilized to reduce future tax payments. The federal and state net operating loss carryforwards will expire between 2015 and 2034 if not utilized. Utilization of the net operating loss carryforwards may be subject to annual limitations due to the ownership percentage change limitations provided by the Internal Revenue Code Section 382 and similar state provisions. To date, we have not completed an analysis in accordance with §382. In the event of a deemed change in control under Internal Revenue Code Section 382, an annual limitation imposed on the utilization of net operating losses may result in the expiration of all or a portion of the net operating loss carryforwards. We also had federal and state research and development credit carryforwards of $7.0 million and $1.9 million, respectively, which begin to expire in 2020 if not utilized. We also had foreign tax credits of approximately $1.0 million that will expire between 2018 and 2021 if not utilized. As of December 31, 2014, we have not been subject to a federal income tax audit in the U.S.

During 2014, the deferred tax valuation allowance increased by approximately $9.1 million, primarily as the result of increases to federal, state, and foreign net operating losses. A full valuation allowance has been recorded in the accompanying consolidated financial statements to offset our U.S. and specific foreign deferred tax assets because the future realizability of such assets is uncertain. We believe that the future realization of these assets is not more likely than not given the expected future tax losses in these jurisdictions.

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The below table details the changes in unrecognized tax benefits, which if recognized would favorably impact our effective tax rate (in thousands):

	Years Ended December 31,
	2014			2013			2012
Balance at beginning of the year	$	411		$	1,067		$	678
Increase in unrecognized tax benefits current year		88			411			389
Decrease in unrecognized tax benefits prior years		(110	)		—			—
Reductions due to audit settlement		(42	)		(1,067	)		—
Balance at end of year	$	347		$	411		$	1,067

As of December 31, 2014 we had gross unrecognized tax benefits of $0.4 million that, if recognized, would result in a reduction of our effective tax rate. As of December 31, 2013 and 2012 we had gross unrecognized tax benefits of $0.5 million and $1.5 million, respectively, including interest and penalties of $0.1 million and $0.4 million.

We monitor the undistributed earnings of foreign subsidiaries and, as necessary, provide for income taxes on those earnings that are not deemed permanently invested. As of December 31, 2014, there were no significant undistributed earnings of foreign subsidiaries that were deemed permanently invested.

12. Stock Plans and Stock-Based Compensation

Stock Incentive Plans

We maintain the 2014 Omnibus Incentive Plan (2014 Plan) that governs awards to both employees and non-employees. The 2014 Plan replaced and superseded our 2005 Stock Incentive Plan (2005 Plan) except that awards granted under the 2005 Plan remain in effect pursuant to their original terms. While the 2014 Plan authorizes a variety of equity-based and cash awards, we generally offer equity incentives under the 2014 Plan in the form of restricted stock units, stock options and performance shares. Restricted stock units customarily vest over a period of three or four years. Stock options expire ten years from the date of grant and customarily vest over a period of four years for employees and are fully vested for directors. Performance shares are issued to certain employees and executive officers and entitle recipients to earn restricted stock units based on the achievement of annual corporate financial performance metrics; any earned restricted stock units customarily vest over a period of three years. We settle stock option exercises and the vesting of restricted stock units with newly issued common shares. Pursuant to the 2014 Plan, each share award other than options or stock appreciation rights will reduce the number of total shares available for grant by 1.62 shares. A total of 5.6 million shares, together with any unissued shares that may carry over from the 2005 Plan, have been authorized for grant under the 2014 Plan and at December 31, 2014, 5.3 million shares remained available for future grant.

We offer a corporate bonus plan for the benefit of our employees. Payout under the bonus plan is based on individual performance and the achievement of certain annual corporate financial performance metrics. Bonus awards are paid in cash or, at the discretion of the Compensation Committee of the Board, in shares of our common stock. The estimated payout under our bonus plan is recognized as compensation expense during the performance year and is classified as a liability, until settlement, on our consolidated balance sheet. The compensation expense associated with our bonus plan for the 2014, 2013 and 2012 performance years that has been or is expected to be paid in shares of our common stock has been classified as stock-based compensation expense.

We also maintain the 2005 Employee Stock Purchase Plan (2005 Purchase Plan), which authorizes the issuance of up to 0.7 million shares of common stock to participating employees through a series of periodic offerings. Each six-month offering period begins in January and July. An employee becomes eligible to participate in the 2005 Purchase Plan once he or she has been employed for at least three months and is regularly

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employed for at least 20 hours per week for more than three months in a calendar year. The price at which employees can purchase common stock in an offering is 95 percent of the closing price of our common stock on the NASDAQ Global Select Market on the lower of the first or last day of the offering period, unless otherwise determined by the Board of Directors or Compensation Committee of the Board. As of December 31, 2014, 0.1 million shares were available for future issuance under the 2005 Purchase Plan.

Stock Options

A summary of the status of stock options granted under all of our plans at December 31, 2014, and changes during the year then ended, is as follows:

Stock Options	Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value		Average Remaining Contractual  Life
						(In thousands)		(In years)
Outstanding at beginning of year		4,825,880		$	10.73
Granted		997,459		$	14.35
Exercised		(1,524,601	)	$	9.04
Forfeited or expired		(196,313	)	$	15.17
Outstanding at end of year		4,102,425		$	12.02	$	24,832		5.18
Fully vested and exercisable		2,822,955		$	11.30	$	19,264		3.73
Fully vested, exercisable and expected to vest		3,956,565		$	11.96	$	24,197		5.06

The aggregate intrinsic value for stock options is calculated based on the market price of our common stock as of December 31, 2014, less the exercise price of the underlying awards, excluding out-of-the-money awards. The total fair value of options that vested during 2014, 2013 and 2012 was $4.9 million, $5.1 million and $5.1 million, respectively. The aggregate intrinsic value of options exercised during 2014, 2013 and 2012 was $9.2 million, $3.5 million and $8.8 million, respectively. The aggregate intrinsic value of options exercised is calculated based on the market price of our common stock on the exercise date, less the exercise price of underlying award.

The weighted-average fair value of options granted during 2014, 2013 and 2012 was $5.80, $6.29 and $9.23 per option, respectively. The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Years Ended December 31,
	2014	2013	2012
Expected life (in years)	4.40 to 5.00	4.50 to 4.70	4.50
Risk-free interest rate	1.56% to 1.69%	0.75% to 1.04%	0.67% to 0.90%
Expected stock price volatility	43% to 45%	62%	70%
Expected dividend yield	—	—	—

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Restricted Stock

The total fair value of restricted stock that vested was $3.2 million, $2.8 million and $3.7 million during 2014, 2013 and 2012, respectively. The weighted-average fair value of restricted stock granted during 2014, 2013 and 2012 was $14.35, $11.97 and $16.89 per unit, respectively. The following table summarizes the status of the unvested restricted stock:

	Shares			Weighted  Average Grant-date Fair Value		Aggregate Intrinsic  Value		Weighted  Average Remaining Contractual Life
						(In thousands)		(In years)
Unvested at December 31, 2013		734,221		$	14.72
Granted		699,913		$	14.35
Vested		(192,741	)	$	16.64
Forfeited		(51,548	)	$	13.94
Unvested at December 31, 2014		1,189,845		$	14.23	$	21,334		1.89

The aggregate intrinsic value for restricted stock is calculated based on the market price of our common stock as of December 31, 2014.

Employee Stock Purchase Plan

The weighted-average fair value of stock purchase rights granted as part of the 2005 Purchase Plan during 2014, 2013 and 2012 was $1.46, $3.10 and $4.57 per share, respectively. The fair value of the employees’ stock purchase rights was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Years Ended December 31,
	2014	2013	2012
Expected life (in months)	6	6	6
Risk-free interest rate	0.07% to 0.10%	0.09% to 0.12%	0.06% to 0.15%
Expected stock price volatility	26.3% to 27.4%	20.1% to 33.6%	23.3% to 36.0%
Expected dividend yield	—	—	—

There were 70,899, 75,301 and 56,691 shares issued under the 2005 Purchase Plan during 2014, 2013 and 2012, respectively, which resulted in share-based compensation expense of $0.1 million, $0.1 million, and $0.2 million in 2014, 2013 and 2012, respectively.

Stock-based Compensation Expense

The following table presents stock-based compensation expense included in the consolidated statements of comprehensive loss (in thousands):

	Years Ended December 31,
	2014		2013		2012
Cost of revenues	$	1,212	$	918	$	1,168
Selling and marketing		4,442		3,171		4,186
Research and development		1,726		1,331		1,372
General and administrative		5,501		3,218		4,677
Total stock-based compensation expense	$	12,881	$	8,638	$	11,403

As of December 31, 2014, approximately $19 million of unrecognized stock compensation cost related to nonvested stock options and restricted stock (net of estimated forfeitures) is expected to be recognized over a weighted-average period of 2.6 years.

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Other Compensation Plans

We maintain postemployment benefit plans for employees in certain foreign subsidiaries. These unfunded plans provide lump sum benefits, payable based on statutory regulations for voluntary or involuntary termination. We have recorded a liability of $1.7 million and $1.8 million at December 31, 2014 and 2013, respectively, as other long-term liabilities for costs associated with these plans. The expense recorded in connection with these plans was not significant during 2014, 2013 and 2012.

13. Employee Benefit Plan

We have a 401(k) retirement plan (401(k) Plan) for the benefit of eligible employees, as defined. Each participant may elect to contribute up to 75% of his or her compensation to the 401(k) Plan each year, subject to certain IRS limitations. We contribute 100% of the first 3% of the employee’s contribution and 50% of the next 2% of the employee’s contribution. We contributed $1.7 million, $1.5 million and $1.3 million to the 401(k) Plan during 2014, 2013 and 2012, respectively.

14. Stockholders’ Equity

We received 196,378, 34,311 and 32,310 shares of common stock that were surrendered in payment for the exercise of stock options during 2014, 2013 and 2012, respectively.

During 2012, we repaid in full all principal and interest in the aggregate amount of $45.2 million under our term loan and security agreement with Asahi through the issuance of 2,456,246 shares of our common stock, which, after the retention by us of 28,351 shares for the payment of certain minimum withholding taxes, resulted in a net issuance to Asahi of 2,427,895 shares.

In connection with the sale of our common stock in a private placement during 2008 we issued warrants to purchase 1,900,000 shares of our common stock. These warrants had an exercise price of $5.50 per share and contained a net share settlement feature. As of December 31, 2013, all warrants had been exercised or had expired.

15. Business Combination

During 2013, we acquired substantially all of the System One assets of Kimal PLC, or Kimal, a distributor of our products in the United Kingdom. The acquisition was consistent with our move to a direct sales model in the United Kingdom. The aggregate purchase price of $4.0 million include cash payments of $0.1 million and $2.2 million paid in 2014 and 2013, respectively, the forgiveness of a capital lease liability due from Kimal of $1.5 million, contingent consideration of $0.5 million paid in 2014 and offset by the reclassification of deferred revenues of $0.3 million, net of related deferred cost of revenues, associated with sales of equipment to Kimal prior to January 1, 2011.

The following table presents the allocation of the purchase price to the estimated fair value of the assets acquired (in thousands):

Assets purchased:
Inventory	$	523
Field Equipment		3,298
Customer relationships		170
Assets acquired	$	3,991

The fair values of inventory and field equipment noted above approximated their net book value at the time of acquisition. The customer relationships were valued using the multi-period excess-earnings method, a form of the income approach, using certain significant unobservable inputs (classified as level 3 in the fair value hierarchy), namely, a discount rate of 11.5%, projected future cash flows, and patient growth rates.

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16. Derivative Instruments and Hedging

We operate a manufacturing and service facility in Mexico and we purchase materials and pay our employees at that facility in pesos, and as such, we are potentially exposed to adverse as well as beneficial movements in foreign currency exchange rates. We enter into foreign exchange forward contracts to minimize the impact of foreign currency exchange rate fluctuations on these peso denominated expenses. These contracts have a duration of up to twelve months and are designated as cash flow hedges. The counterparties to these foreign exchange forward contracts are creditworthy financial institutions; therefore, we do not consider the risk of counterparty nonperformance to be material. The notional amount of our outstanding contracts that are designated as cash flow hedges was $12.5 million and $10.4 million at December 31, 2014 and December 31, 2013, respectively. The fair value of these contracts was recorded on the balance sheet within prepaid expenses and other current assets or other current liabilities depending on the gain (loss) position. The fair value of these contracts was a liability of $1.3 million and $0.2 million at December 31, 2014 and December 31, 2013, respectively.

Gains or losses related to hedge ineffectiveness recognized in earnings were not material during 2014 or 2013. Given the short-term nature of our contracts any gains or losses recorded within accumulated other comprehensive income (loss) will be recognized in earnings within the next twelve months.

The following table presents the effect of these contracts designated as cash flow hedges on our consolidated financial statements (in thousands):

	Gain (Loss) Recognized in  OCI (Effective Portion)			Gain (Loss) Reclassified from OCI into Income (Effective Portion)			Classification within the Condensed Consolidated Statement of  Comprehensive Loss
Year Ended December 31, 2014	$	(1,223	)	$	(258	)		Cost of revenues
Year Ended December 31, 2013	$	144		$	656			Cost of revenues
Year Ended December 31, 2012	$	498		$	109			Cost of revenues

17. Accumulated Other Comprehensive (Loss) Income

The following additional information is provided with respect to the accumulated other comprehensive (loss) income as presented on the condensed consolidated balance sheets (in thousands):

	Unrealized gain (loss) on derivative instruments			Other (2)			Total
Balance, net of tax, as of December 31, 2011	$	—		$	(68	)	$	(68	)
Other comprehensive income before reclassifications		498			149			647
Gain reclassified to earnings (1)		(109	)		—			(109	)
Total other comprehensive income		389			149			538
Balance, net of tax, as of December 31, 2012	$	389		$	81		$	470
Other comprehensive income before reclassifications		144			254			398
Gain reclassified to earnings (1)		(656	)		—			(656	)
Total other comprehensive income (loss)		(512	)		254			(258	)
Balance, net of tax, as of December 31, 2013	$	(123	)	$	335		$	212
Other comprehensive loss before reclassifications		(1,223	)		(1,439	)		(2,662	)
Loss reclassified to earnings (1)		258			—			258
Total other comprehensive loss		(965	)		(1,439	)		(2,404	)
Balance, net of tax, as of December 31, 2014	$	(1,088	)	$	(1,104	)	$	(2,192	)

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(1) Reclassifications of gains (losses) on derivative instruments are included in cost of revenues on the consolidated statement of comprehensive loss. See Note 16 for further information.

(2) Other includes cumulative translation adjustments and, to a lesser extent, pension benefits.

18. Fair Value Measurements

The following tables present assets and liabilities measured at fair value on a recurring basis and their level within the value hierarchy (in thousands):

December 31, 2014	Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)		Total Fair Value
Assets
Money market funds(1)	$	39,779	$	—	$	—	$	39,779
Liabilities
Foreign exchange forward contracts(2)	$	—	$	1,265	$	—	$	1,265

December 31, 2013	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value
Assets
Money market funds(1)	$	69,779	$	—	$	—	$	69,779
Foreign exchange forward contracts(2)		—		34		—		34
Liabilities
Foreign exchange forward contracts(2)	$	—	$	192	$	—	$	192
Contingent consideration liability(3)		—		—		540		540

(1) Money market funds are included within cash and cash equivalents.

(2) Foreign exchange forward contracts are included within prepaid expenses and other current assets or other current liabilities depending on the gain (loss) position.

(3) Net present value of expected payments under contingent consideration liability are reported in accrued expenses.

We did not have any transfers between Level 1 and Level 2 during the twelve months ended December 31, 2014 or 2013.

The following table presents the rollforward of the contingent consideration liability classified as Level 3 within the value hierarchy (in thousands):

Balance at December 31, 2013	$	540
Less Payments made		(540	)
Balance at December 31, 2014	$	—

Our contingent consideration liability related to deferred payments made in January and April 2014 in connection with our acquisition of substantially all of the System One assets of Kimal PLC, a distributor of our products in the United Kingdom, on April 2, 2013. The liability recorded at December 31, 2013 was measured using probability weighted discounted cash flow method and includes certain significant unobservable inputs, namely, a discount rate of 11.5% and patient growth rates.

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We measure the fair value of our foreign exchange forward contracts classified as derivative instruments using an income approach, based on prevailing market forward rates less the contract rate multiplied by the notional amount. The product of this calculation is then adjusted for counterparty risk.

The carrying amount of our long-term debt approximates fair value at December 31, 2014. The fair value of our long-term debt was estimated using inputs derived principally from market observable data, including current rates offered to us for debt of the same or similar remaining maturities. Within the hierarchy of fair value measurements, these are level 2 inputs.

The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, accounts receivable, prepaid expenses and other current and non-current assets, accounts payable and accrued expenses approximate fair value due to their short-term nature.

19. Supplemental Cash Flow Information

The following additional information is provided with respect to the consolidated statements of cash flows (in thousands):

	Years Ended December 31,
	2014		2013		2012
Supplemental Disclosures:
Cash paid for interest	$	671	$	549	$	1,457
Cash paid for taxes		903		1,181		586
Noncash Investing and Financing Activities:
Transfers from inventory to field equipment	$	25,370	$	13,827	$	12,172
Transfers from field equipment to deferred cost of revenues		13,110		10,260		10,360
Payment of Corporate Bonus Plan in common stock		—		1,034		878
Market value of shares received in payment for exercise of stock options		3,026		412		513
Construction-in-process financed by construction liability		4,898		3,568		8,343
Settlement of debt through the issuance of common stock		—		—		45,219
Leasehold improvements paid by the landlord		—		—		4,300
Property and equipment acquired under capital lease		76		745		1,615
Acquisition of business		—		1,757		—
Increase in deferred revenues related to the new manufacturing facility in Germany		3,608		—		6,124
Deferred revenues and deferred costs related to acquiree recorded as a reduction of consideration paid		—		335		—

20. Quarterly Financial Data (Unaudited)

The following table sets forth selected quarterly information (unaudited) (in thousands, except per share data):

	Three Months Ended
	March 31, 2014			June 30, 2014			September 30, 2014			December 31, 2014
Revenues	$	72,221		$	74,083		$	75,286		$	79,911
Gross profit		28,934			27,530			28,587			30,852
Loss from operations		(4,789	)		(6,651	)		(6,274	)		(4,473	)
Net loss attributable to stockholders of NxStage Medical, Inc.		(5,275	)		(7,113	)		(6,706	)		(4,852	)
Net loss per share, basic and diluted	$	(0.09	)	$	(0.12	)	$	(0.11	)	$	(0.08	)

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	Three Months Ended
	March 31, 2013			June 30, 2013			September 30, 2013			December 31, 2013
Revenues	$	61,644		$	65,462		$	66,873		$	69,450
Gross profit		24,000			25,087			25,528			27,888
Loss from operations		(4,536	)		(4,271	)		(4,413	)		(4,578	)
Net loss attributable to stockholders of NxStage Medical, Inc.		(4,994	)		(3,405	)		(4,986	)		(5,176	)
Net loss per share, basic and diluted	$	(0.08	)	$	(0.06	)	$	(0.08	)	$	(0.08	)

Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure

None.

Item 9A. Controls and Procedures

Our management, with the participation of our chief executive officer and chief financial officer, evaluated the effectiveness of our disclosure controls and procedures as of December 31, 2014. The term “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Securities and Exchange Act of 1934, or the Exchange Act, means controls and other procedures of a company that are designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported, within the time periods specified in the SEC’s rules and forms. Disclosure controls and procedures include, without limitation, controls and procedures designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is accumulated and communicated to the company’s management, including its principal executive and principal financial officers, as appropriate to allow timely decisions regarding required disclosure. Our management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures. Based on the evaluation of our disclosure controls and procedures as of December 31, 2014, our chief executive officer and chief financial officer concluded that, as of such date, our disclosure controls and procedures were effective to achieve their stated purpose.

No change in our internal control over financial reporting (as defined in Rule 13a-15(f) and 15d-15(f) under the Exchange Act) occurred during the three months ended December 31, 2014 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

Management’s Report on Internal Control over Financial Reporting

We, as management of NxStage Medical, Inc., are responsible for establishing and maintaining adequate internal control over financial reporting. Pursuant to the rules and regulations of the Securities and Exchange Commission, internal control over financial reporting is a process designed by, or under the supervision of, the company’s principal executive and principal financial officer, or persons performing similar functions, and effected by the company’s board of directors, management and other personnel, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles and includes those policies and procedures that:

• Pertain to the maintenance of records that in reasonable detail accurately and fairly reflect the transactions and dispositions of our assets;

• Provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that our receipts and expenditures are being made only in accordance with authorizations of our management and directors; and

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• Provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of our assets that could have a material effect on our financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Management has evaluated the effectiveness of its internal control over financial reporting as of December 31, 2014, based on the control criteria established in a report entitled Internal Control—Integrated Framework, issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework).

Based on such evaluation, we have concluded that NxStage’s internal control over financial reporting is effective as of December 31, 2014.

The independent registered public accounting firm of Ernst & Young LLP, as auditors of NxStage’s consolidated financial statements, has issued an attestation report on its assessment of NxStage’s internal control over financial reporting.

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REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Board of Directors and Shareholders of NxStage Medical, Inc.

We have audited NxStage Medical, Inc.’s internal control over financial reporting as of December 31, 2014, based on criteria established in Internal Control - Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 Framework) (the COSO criteria). NxStage Medical, Inc.’s management is responsible for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting included in the accompanying Management’s Report on Internal Control over Financial Reporting. Our responsibility is to express an opinion on the company’s internal control over financial reporting based on our audit.

We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

In our opinion, NxStage Medical, Inc. maintained, in all material respects, effective internal control over financial reporting as of December 31, 2014, based on the COSO criteria.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States), the consolidated balance sheets of NxStage Medical, Inc. as of December 31, 2014 and 2013, and the related consolidated statements of comprehensive loss, changes in stockholders’ equity, and cash flows for each of the three years in the period ended December 31, 2014, and our report dated February 26, 2015 expressed an unqualified opinion thereon.

/s/    Ernst & Young LLP

Boston, Massachusetts

February 26, 2015

109

Item 9B. Other Information

None.

PART III

Item 10. Directors, Executive Officers and Corporate Governance

We have included information about our executive officers in Part I of this Annual Report under the caption “Executive Officers”. Certain documents relating to our corporate governance, including our Code of Business Conduct and Ethics, which is applicable to our directors, officers and employees, and the charters of the Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee of our Board of Directors, are available on our website at www.nxstage.com. We intend to make all required disclosures regarding any amendments to, or waivers from, provisions of our Code of Business Conduct and Ethics on our website. We include our website address in this Annual Report only as an inactive textual reference and do not intend it to be an active link to our website.

The response to the remainder of this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Election of Directors,” “Corporate Governance,” and “Other Matters — Section 16(a) Beneficial Ownership Reporting Compliance” contained in the proxy statement for our 2015 annual meeting of stockholders.

Item 11. Executive Compensation

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Information About Executive and Director Compensation” and “Corporate Governance” contained in the proxy statement for our 2015 annual meeting of stockholders.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Stock Ownership of Certain Beneficial Owners and Management” and “Information About Executive and Director Compensation” contained in the proxy statement for our 2015 annual meeting of stockholders.

Item 13. Certain Relationships and Related Transactions, and Director Independence

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Certain Relationships and Related Transactions” and “Corporate Governance” contained in the proxy statement for our 2015 annual meeting of stockholders.

Item 14. Principal Accountant Fees and Services

The response to this item is incorporated by reference from the discussion responsive thereto in the section entitled “Corporate Governance” contained in the proxy statement for our 2015 annual meeting of stockholders.

110

PART IV

Item 15. Exhibits and Financial Statement Schedules

(a) Financial Statements

The following consolidated financial statements are filed as part of this Annual Report under “Item 8 — Financial Statements and Supplementary Data”:

Report of Independent Registered Public Accounting Firm	77
Consolidated Balance Sheets	78
Consolidated Statements of Comprehensive Loss	79
Consolidated Statements of Changes in Stockholders’ Equity	80
Consolidated Statements of Cash Flows	82
Notes to Consolidated Financial Statements	83

(b) Exhibits

The exhibits listed in the Exhibit Index immediately preceding the exhibits are incorporated herein by reference and are filed as part of this Annual Report.

(c) Financial Statement Schedules

None.    No financial statement schedules have been filed as part of this Annual Report because they are either not applicable or the required information has been included in the accompanying notes to the consolidated financial statements.

111

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this Annual Report on Form 10-K to be signed on its behalf by the undersigned, thereunto duly authorized.

NXSTAGE MEDICAL, INC.
By:	/s/    Jeffrey H. Burbank
	Jeffrey H. Burbank
	Chief Executive Officer
	February 26, 2015

Pursuant to the requirements of the Securities Exchange Act of 1934, this Annual Report on Form 10-K has been signed below by the following persons on behalf of the Registrant in the capacities and on the dates indicated.

Signature	Title	Date
/s/    Jeffrey H. Burbank        Jeffrey H. Burbank	Chief Executive Officer and Director (Principal Executive Officer)	February 26, 2015
/s/    Matthew W. Towse         Matthew W. Towse	Chief Financial Officer and Senior Vice President (Principal Financial and Accounting Officer)	February 26, 2015
/s/    Robert G. Funari        Robert G. Funari	Chairman of the Board of Directors	February 26, 2015
/s/    Daniel A. Giannini        Daniel A. Giannini	Director	February 26, 2015
/s/    Earl R. Lewis        Earl R. Lewis	Director	February 26, 2015
/s/    Jean K. Mixer         Jean K. Mixer	Director	February 26, 2015
/s/    Craig W. Moore         Craig W. Moore	Director	February 26, 2015
/s/    Reid S. Perper         Reid S. Perper	Director	February 26, 2015
/s/    Barry M. Straube                    Barry M. Straube, M.D.	Director	February 26, 2015

112

EXHIBIT INDEX

			Incorporated by Reference to^
Exhibit Number	Description	Form or Schedule	Exhibit No.		Filing Date with SEC
3.1	Restated Certificate of Incorporation	S-1/A		3.4	10/7/2005
3.2	Amended and Restated By-Laws	S-1/A		3.5	10/7/2005
4.1	Specimen certificate evidencing shares of common stock	S-1/A		4.1	10/7/2005
10.1#	1999 Stock Option and Grant Plan, as amended by Amendments Nos. 1-3	S-1/A		10.1	10/7/2005
10.2#	Form of Incentive Stock Option Agreement under the 1999 Stock Option and Grant Plan	S-1/A		10.2	10/7/2005
10.3#	Form of Nonstatutory Stock Option Agreement under the 1999 Stock Option and Grant Plan	S-1/A		10.3	10/7/2005
10.4#	2005 Stock Incentive Plan, as amended	DEF 14A		Appendix B	4/28/2011
10.5#	Forms of Incentive Stock Option Agreement and Nonstatutory Stock Option Agreement under the 2005 Stock Incentive Plan	S-1/A		10.22	10/20/2005
10.6#	Form of Restricted Stock Agreement under the 2005 Stock Incentive Plan	10-K		10.5	3/16/2007
10.7#	Form of Restricted Stock Unit Agreement under the 2005 Stock Incentive Plan	10-Q		10.3	5/8/2014
10.8#	2014 Omnibus Incentive Plan	DEF 14A		Appendix B	4/24/2014
*10.9#	Form of Stock Option Agreement under the 2014 Omnibus Incentive Plan
*10.10#	Form of Restricted Stock Unit Agreement under the 2014 Omnibus Incentive Plan
*10.11#	Form of Performance Share Award Agreement under the 2014 Omnibus Incentive Plan
10.12#	2005 Employee Stock Purchase Plan, as amended	DEF 14A		Appendix B	4/24/2009
10.13#	Employment Agreement dated October 19, 2005 between the Registrant and Jeffrey H. Burbank	S-1/A		10.12	10/20/2005
10.14#	Employment Agreement dated October 18, 2005 between the Registrant and Joseph E. Turk, Jr.	S-1/A		10.15	10/20/2005
10.15#	Employment Agreement dated October 18, 2005 between the Registrant and Winifred L. Swan	S-1/A		10.16	10/20/2005
10.16#	Employment Agreement dated November 27, 2006 between the Registrant and Robert S. Brown	10-K		10.10	3/16/2007
10.17#	Employment Agreement dated as of July 15, 2013 between the Registrant and Matthew W. Towse	10-Q		10.2	11/7/2013
10.18#	Form of Indemnification Agreement entered into between the Registrant and each of its Directors and Executive Officers	S-1/A		10.21	9/21/2005
10.19#	Director Compensation Policy	10-Q		10.3	11/7/2013

113

			Incorporated by Reference to^
Exhibit Number	Description	Form or Schedule	Exhibit No.		Filing Date with SEC
10.20	Credit Agreement dated as of June 9, 2014 among the Registrant and certain of its subsidiaries, General Electric Capital Corporation and Silicon Valley Bank	10-Q		10.1	8/7/2014
10.21†	Second Amended and Restated National Service Provider Agreement dated as of March 1, 2013 between the Registrant and DaVita Healthcare Partners Inc.	10-Q		10.1	7/25/2013
10.22†	Chronic Outpatient Therapy Agreement, as amended through January 10, 2014, between the Registrant and Fresenius USA Marketing, Inc.	10-Q/A		10.1	10/1/2014
10.23†	Supply Agreement dated as of January 5, 2007 between the Registrant and Membrana GmbH	10-K		10.27	3/16/2007
10.24†	Supply Agreement dated April 10, 2009 between the Registrant and Laboratorios PiSA SA de C.V.	10-Q/A		10.45	10/19/2009
10.25†	Amendment to Supply Agreement dated as of July 22, 2013 between Medisystems Corporation and Laboratorios PiSA SA de C.V.	10-Q		10.1	11/7/2013
10.26†	Extracorporeal Disposables Distribution Agreement dated June 15, 2009 between Medisystems Corporation and Gambro Renal Products, Inc.	10-Q		10.46	8/7/2009
10.27†	Amendment to Extracorporeal Disposables Distribution Agreement dated January 2, 2014 between the Registrant and Gambro Renal Products, Inc.	10-Q		10.20	5/8/2014
10.28†	Technology and Trademark License Agreement effective June 15, 2009 between the Registrant and Asahi Kasei Kuraray Medical Co., Ltd.	10-Q		10.48	8/7/2009
10.29†	Lease dated as of June 22, 2011 between Registrant and 350 Riverwalk, LLC	10-Q/A		10.33	10/7/2011
*21	List of Subsidiaries
*23	Consent of Ernst & Young LLP
*31.1	Certification of Chief Executive Officer pursuant to Exchange Act Rules 13a-14a or 15d-14a, as adopted pursuant to Section 302 of Sarbanes-Oxley Act of 2002
*31.2	Certification of Chief Financial Officer pursuant to Exchange Act Rules 13a-14a or 15d-14a, as adopted pursuant to Section 302 of Sarbanes-Oxley Act of 2002
**32.1	Certification of Chief Executive Officer pursuant to Exchange Act Rules 13a-14(b) or 15d-14(b) and 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of Sarbanes-Oxley Act of 2002
**32.2	Certification of Chief Financial Officer pursuant to Exchange Act Rules 13a-14(b) or 15d-14(b) and 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of Sarbanes-Oxley Act of 2002

114

			Incorporated by Reference to^
Exhibit Number	Description	Form or Schedule	Exhibit No.	Filing Date with SEC
*101.INS	XBRL Instance Document
*101.SCH	XBRL Taxonomy Extension Schema
*101.CAL	XBRL Taxonomy Extension Calculation Linkbase
*101.DEF	XBRL Taxonomy Extension Definition Linkbase
*101.LAB	XBRL Taxonomy Extension Label Linkbase
*101.PRE	XBRL Taxonomy Extension Presentation Linkbase

^ Exhibits previously filed with the Securities and Exchange Commission as exhibits to Form S-1 or S-1/A were filed under Commission File Number 333-126711. All other previously filed exhibits were filed under Commission File Number 0-51567.

* Filed herewith.

** Furnished herewith.

† Confidential treatment has been granted or requested with respect to portions of this exhibit. Confidential portions are omitted and filed separately with the Securities and Exchange Commission.

# Management contract or compensatory plan or arrangement.

115

EX-10.9

Exhibit 10.9

Stock Option Agreement

Granted Under NxStage Medical, Inc. 2014 Omnibus Incentive Plan

1. Grant of Option.

This agreement evidences the grant by NxStage Medical, Inc., a Delaware corporation (“Company”), to the Grantee listed below of an option to purchase shares of the Company’s Stock (“Shares”), as outlined below:

Grantee: <first_name> <middle_name> <last_name>

Shares: <shares_awarded>

Option Price per Share: <award_price>

Option Type: <award_type_code>

Grant Date: <award_date>

Final Exercise Date: 5:00 p.m. ET on <expire_date>

Except as otherwise indicated by the context, “Grantee” shall be deemed to include any person who acquires the right to exercise this option validly under its terms. If the Option Type listed above is “Non-qualified Stock Option” or “NQ,” then this option shall not be an incentive stock option as defined in Section 422 of the Code. If the Option Type listed above is “Incentive Stock Option” or “ISO,” then this option is intended to qualify as an incentive stock option as defined in Section 422 of the Code. Notwithstanding the foregoing, if the Grantee ceases to be an Employee of the Company or any corporate Subsidiary but continues to provide Service, this option will be deemed a Non-qualified Stock Option as of the date 3 months and 1 day after the Grantee ceases to be an Employee of the Company or any corporate Subsidiary. In addition, to the extent that all or part of an option intended to be an “Incentive Stock Option” exceeds the “$100,000 per year limitation” rule of Section 422(d) of the Code, the option or the lesser excess part will be deemed to be a Non-qualified Stock Option.

This option is granted in consideration of Service rendered and to be rendered by the Grantee to the Company or an Affiliate. This option is subject to the terms of this agreement and the Company’s 2014 Omnibus Incentive Plan (“Plan”), a copy of which is furnished to the Grantee with this agreement. Any capitalized term that is not defined in this agreement shall have the meaning ascribed to it in the Plan.

2. Vesting Schedule.

This option will become exercisable (“vest”) for the Shares and on the dates indicated on Schedule A to this agreement, provided that the Grantee continues to provide Service to the Company or an Affiliate on such dates and has provided Service at all times since the Grant Date.

3. Exercise of Option.

(a) Right of Exercise. The Grantee’s right of exercise will be cumulative so that to the extent this option is not exercised in any period to the maximum extent permissible, this option will continue to be exercisable with respect to any remaining Shares for which it is vested until this option terminates. No partial exercise of this option may be for any fractional Share or for fewer than ten whole Shares.

1

(b) Form of Exercise. Each election to exercise this option must be in writing on the form specified by the Company and received by the Company at its principal office.

(c) Payment of Option Price and Withholding Taxes. The Grantee must pay to the Company the Option Price and, if the Grantee is an Employee, all applicable federal, state or local withholding taxes required by law to be withheld in respect of this option or the Shares:

– in cash;

– by delivery (on a form acceptable to the Company) of an irrevocable direction to a licensed securities broker acceptable to the Company to sell Shares and to deliver proceeds from such sale to the Company in payment of the Option Price and all applicable withholding taxes; or

– if the Grantee is a director or officer of the Company subject to Section 16 of the Exchange Act, by tender of previously acquired and unencumbered shares of the Company’s Stock equal in value to the Option Price and all applicable withholding taxes.

In addition, the Company may deduct from payments of any kind otherwise due to the Grantee the Option Price and all applicable withholding taxes in respect of this option or the Shares. The Company may, in its discretion, permit the Grantee to make alternative arrangements for payment of such amounts. The Grantee understands that the Grantee (and not the Company) shall be responsible for the Grantee’s own tax liability that may result from this investment or the transactions contemplated by this agreement.

(d) Issued Shares. All Shares will be issued in the name of the Grantee in book entry form only.

4. Termination – Employees and Consultants.

The termination provisions in this section apply to Grantees who are Employees of, or consultants or advisors to (excluding Outside Directors), the Company or an Affiliate as of the Grant Date.

(a) Continuous Relationship with the Company or an Affiliate Required. Except as otherwise provided in this section, this option will terminate on the earlier of (1) the Grantee ceasing to provide Service to the Company or an Affiliate for any reason and (2) the Final Exercise Date.

(b) Death or Disability. If the Grantee ceases to provide Service due to his or her death or disability (within the meaning of Section 22(e)(3) of the Code) and the Company has not terminated the Grantee for Cause, this option will terminate on the earlier of (1) 5:00 p.m. ET on the date that is exactly 1 year after the Grantee ceases to provide Service due to his or her death or disability and (2) the Final Exercise Date.

(c) Certain Other Terminations. If the Grantee ceases to provide Service for any reason other than due to his or her death or disability (within the meaning of Section 22(e)(3) of the Code) and the Company has not terminated the Grantee for Cause, this option will terminate on the earlier of (1) 5:00 p.m. ET on the date that is exactly 3 months after the Grantee ceases to provide Service and (2) the Final Exercise Date. Notwithstanding the foregoing, if the Grantee violates the non-competition, confidentiality or non-solicitation provisions of any employment contract, confidentiality and nondisclosure agreement, or other agreement between the Grantee and the Company, this option will terminate immediately upon such violation.

2

5. Termination – Directors.

The termination provisions in this section apply to Grantees who are Outside Directors of the Company as of the Grant Date.

(a) 3+ Years of Service. If the Grantee ceases to provide Service and at such time has completed three or more full years of Service as a member of the Board, this option will terminate on the Final Exercise Date.

(b) < 3 Years of Service. If the Grantee ceases to provide Service and at such time has completed less than three full years of Service as a member of the Board, this option will terminate on the earlier of (1) 5:00 p.m. ET on the date that is exactly 3 months after the Grantee ceases to provide Service and (2) the Final Exercise Date.

6. Transfer Restrictions.

This option may not be sold, assigned, transferred, pledged or otherwise encumbered by the Grantee, either voluntarily or by operation of law, except by will or the laws of descent and distribution, and during the lifetime of the Grantee this option shall be exercisable only by the Grantee. If the Option Type listed above is “Non-qualified Stock Option” or “NQ,” then this option may be transferred pursuant to a domestic relations order in settlement of marital property rights.

7. Disqualifying Dispositions of Incentive Stock Option Shares.

If the Option Type listed above is “Incentive Stock Option” or “ISO,” the Grantee understands that in order to obtain the benefits of an incentive stock option under Section 422 of the Code, among other conditions, no sale or other disposition may be made of any Shares acquired upon exercise of this option within 1 year after such Shares were acquired pursuant to such exercise, nor within 2 years after the Grant Date. If the Grantee intends to dispose, or does dispose (whether by sale, exchange, gift, transfer or otherwise, including “sell-to-cover” dispositions), of any such Shares within said periods, the Grantee must notify the Company about such disposition in writing within 10 days after such disposition, and provide any other information regarding such disposition that the Company may require.

IN WITNESS WHEREOF, the Company has caused this agreement to be executed by its duly authorized officer.

NxStage Medical, Inc.
By:
	Jeffrey H. Burbank
	Chief Executive Officer

3

Grantee’s Acceptance

The undersigned hereby accepts the terms of this agreement and acknowledges receipt of a copy of the Company’s 2014 Omnibus Incentive Plan and related prospectus.

Grantee: /s/ <first_name> <middle_name> <last_name>

Address:

<address_1>

<address_2>

<city>, <state>

<zip>

<country>

4

Schedule A to Stock Option Agreement

Subject to the terms of this Stock Option Agreement and the Plan, this option will become exercisable (“vest”) for the Shares and on the dates indicated on this Schedule A, provided that the Grantee continues to provide Service to the Company or an Affiliate on such dates and has provided Service at all times since the Grant Date:

<vesting_schedule>

5

EX-10.10

Exhibit 10.10

Restricted Stock Unit Agreement

Granted Under NxStage Medical, Inc. 2014 Omnibus Incentive Plan

1. Grant of Restricted Stock Units.

This agreement evidences the grant by NxStage Medical, Inc., a Delaware corporation (“Company”), to the Grantee listed below of restricted stock units (“RSUs”) representing the conditional right to receive shares of the Company’s Stock (“Shares”), as outlined below:

Grantee: <first_name> <middle_name> <last_name>

Shares: <shares_awarded>

Grant Date: <award_date>

Except as otherwise indicated by the context, “Grantee” shall be deemed to include any person who acquires these RSUs validly under their terms.

These RSUs are granted in consideration of Service rendered and to be rendered by the Grantee to the Company or an Affiliate. These RSUs are subject to the terms of this agreement and the Company’s 2014 Omnibus Incentive Plan (“Plan”), a copy of which is furnished to the Grantee with this agreement. Any capitalized term that is not defined in this agreement shall have the meaning ascribed to it in the Plan.

2. Vesting.

(a) Schedule. These RSUs will become nonforfeitable (“vest”) with respect to the Shares and on the dates indicated on Schedule A to this agreement, provided that the Grantee continues to provide Service to the Company or an Affiliate on such dates and has provided Service at all times since the Grant Date.

(b) Issued Shares. Promptly following any vesting of these RSUs, the Company will issue the portion of Shares listed above that corresponds to the applicable vesting date in full settlement of such vested RSUs. All Shares will be issued in the name of the Grantee in book entry form only.

3. Withholding Taxes.

This Section 3 only applies to Grantees who are Employees. Paragraph (a) below applies to a Grantee who is an officer of the Company subject to Section 16 of the Exchange Act and Paragraph (b) below applies to all other Grantees.

(a) Certain Officers. The Grantee acknowledges and agrees, as a condition of this grant, that the Grantee will pay all applicable federal, state or local withholding taxes required by law to be withheld in respect of these RSUs or the Shares by hereby directing the Company to withhold, from the Shares otherwise issuable to the Grantee, a number of Shares in an amount reasonably determined by the Company to be materially sufficient to satisfy such withholding taxes.

(b) All Other Employees. The Grantee acknowledges and agrees, as a condition of this grant, that the Grantee will pay all applicable federal, state or local withholding taxes required by law to be withheld in respect of these RSUs or the Shares by the sale of Shares in an amount reasonably determined by the Company to be materially sufficient to satisfy such withholding taxes and to deliver proceeds from such sale to the Company in payment of such withholding taxes. In order to authorize such sale, this agreement constitutes an irrevocable direction by the Grantee to a licensed securities broker selected from time to time by the Company, which as of the Grant Date is Charles Schwab & Co, to sell such Shares at the market price on or about the applicable vesting date (with the date of such sale to be at the sole discretion of the selected broker), deliver such sale proceeds to the Company in payment of such withholding taxes, and provide to the Company a duplicate confirmation of such sale. The Grantee must establish the necessary account with the selected broker before the first vesting date for this grant. The Grantee is responsible for providing to the selected broker all applicable forms necessary to facilitate this transaction.

In addition, the Company may deduct from payments of any kind otherwise due to the Grantee all applicable withholding taxes in respect of these RSUs or the Shares. The Company may, in its discretion, permit the Grantee to make alternative arrangements for payment of such amounts. The Grantee understands that the Grantee (and not the Company) shall be responsible for the Grantee’s own tax liability that may result from this investment or the transactions contemplated by this agreement.

4. Termination.

If the Grantee ceases to provide Service to the Company or an Affiliate for any reason, all of the then unvested RSUs will be forfeited immediately and automatically, without the payment of any consideration to the Grantee, effective as of the time that the Grantee ceases to provide Service.

5. Transfer Restrictions.

These RSUs may not be sold, assigned, transferred, pledged or otherwise encumbered by the Grantee, either voluntarily or by operation of law, except by will or the laws of descent and distribution or pursuant to a domestic relations order in settlement of marital property rights.

IN WITNESS WHEREOF, the Company has caused this agreement to be executed by its duly authorized officer.

NxStage Medical, Inc.
By:
	Jeffrey H. Burbank Chief Executive Officer

2

Grantee’s Acceptance

The undersigned hereby accepts the terms of this agreement and acknowledges receipt of a copy of the Company’s 2014 Omnibus Incentive Plan and related prospectus.

Grantee: /s/ <first_name> <middle_name> <last_name>

Address:

<address_1>

<address_2>

<city>, <state>

<zip>

<country>

3

Schedule A to Restricted Stock Unit Agreement

Subject to the terms of this Restricted Stock Unit Agreement and the Plan, these RSUs will become nonforfeitable (“vest”) with respect to the Shares and on the dates indicated on this Schedule A, provided that the Grantee continues to provide Service to the Company or an Affiliate on such dates and has provided Service at all times since the Grant Date:

<vesting_schedule>

4

EX-10.11

Exhibit 10.11

Performance Share Award Agreement

Granted Under NxStage Medical, Inc. 2014 Omnibus Incentive Plan

1. Grant of Performance Shares.

This agreement evidences the grant by NxStage Medical, Inc., a Delaware corporation (the “Company”), to the Participant listed below of performance shares representing the conditional right to receive restricted stock units (“RSUs”), as outlined below:

Participant:	<first_name> <middle_name> <last_name>
RSUs:	<RSUs_awarded>
Grant Date:	<award_date>

Except as otherwise indicated by the context, “Participant” shall be deemed to include any person who acquires these performance shares validly under their terms.

These performance shares are granted in consideration of employment services rendered and to be rendered by the Participant to the Company. These performance shares are subject to the terms of this agreement and the Company’s 2014 Omnibus Incentive Plan (the “Plan”), a copy of which is furnished to the Participant with this agreement. Any capitalized term that is not defined in this agreement shall have the meaning ascribed to it in the Plan.

2. Vesting.

(a) Performance Shares. These performance shares will become nonforfeitable (“vest”), and result in the following number of RSUs to be earned, upon achieving the following performance goals for <performance_period>:

[Targets]

RSUs

*Targets are in millions. Performance goals exclude non-operating activities such as divestitures, and other non-operating items that may arise that were not included in the plan. Performance goals should be measured by applying the same accounting principles, tax laws or other laws or provisions in effect at the time of preparing the performance goals set forth above, without regard to whether there was a change in application of accounting principles, tax laws or other laws or provisions at a later date.

Performance in-between specific goals will result in the number of RSUs earned to be interpolated between the corresponding amounts in the table above.

(b) RSUs. Any earned RSUs will in turn represent the conditional right to receive shares of the Company’s common stock, $0.001 par value per share (the “Shares”), on a one-for-one basis, and will vest on the dates and with respect to the portion of Shares indicated below, provided that the Participant is an Eligible Participant on such dates:

Date	Portion of Shares Vesting On Such Date
The date the Company’s Compensation Committee determines the achievement of the performance goals described in Section 2(a) (the “Determination Date”)	1/3
The first anniversary of the Determination Date	1/3
The second anniversary of the Determination Date	1/3

“Eligible Participant” means a Participant that is, and at all times since the Grant Date has been, an employee, officer or director of, or consultant or advisor to, the Company or an Affiliate of the Company.

Any earned RSUs will be granted pursuant to, and be subject to the terms and conditions set forth in, a separate restricted stock unit agreement to be entered into between the Company and the Participant.

3. Withholding Taxes.

This Section 3 only applies to Participants who are Employees. The Company may deduct from payments of any kind otherwise due to the Participant all applicable federal, state or local withholding taxes required by law to be withheld in respect of these performance shares or the RSUs.

4. Termination.

If the Participant ceases to be an Eligible Participant for any reason, all of the then unvested performance shares, unearned RSUs and unvested Shares will be forfeited immediately and automatically, without the payment of any consideration to the Participant, effective as of the time that the Participant ceases to be an Eligible Participant.

5. Transfer Restrictions.

These performance shares may not be sold, assigned, transferred, pledged or otherwise encumbered by the Participant, either voluntarily or by operation of law, except by will or the laws of descent and distribution or pursuant to a domestic relations order in settlement of marital property rights.

*  *  *

IN WITNESS WHEREOF, the Company has caused this agreement to be executed by its duly authorized officer under its corporate seal.

NxStage Medical, Inc.
By:
	Jeffrey H. Burbank Chief Executive Officer

2

PARTICIPANT’S ACCEPTANCE

The undersigned hereby accepts the terms and conditions of this agreement and acknowledges receipt of a copy of the Company’s 2014 Omnibus Incentive Plan and related prospectus.

Participant:

Address:

3

EX-21

Exhibit 21

Subsidiaries of the Registrant

Name	Jurisdiction of Incorporation
EIR Medical, Inc.	Massachusetts
MediMexico S. de R.L. de C.V.	Mexico
Medisystems Corporation	Washington
Medisystems Europe S.p.A	Italy
Medisystems Services, Inc.	Nevada
NKC Boca Raton, LLC	Delaware
NxStage Boston North, LLC	Delaware
NxStage Boston South, LLC	Delaware
NxStage Cincinnati, LLC	Delaware
NxStage Cleveland, LLC	Delaware
NxStage Columbus, LLC	Delaware
NxStage GmbH & Co. KG	Germany
NxStage Greenbelt, LLC	Delaware
NxStage Jacksonville, LLC	Delaware
NxStage Kidney Care, Inc.	Delaware
NxStage Medical Canada, Inc.	British Columbia
NxStage Medical UK, LTD	United Kingdom
NxStage Oak Brook, LLC	Delaware
NxStage Orlando North, LLC	Delaware
NxStage Orlando South, LLC	Delaware
NxStage Pittsburgh East, LLC	Delaware
NxStage St. Louis, LLC	Delaware
NxStage Tech GmbH	Germany
NxStage Verwaltungs—GmbH	Germany

* Pursuant to Item 601(b)(21)(ii) of Regulation S-K, the names of other subsidiaries of NxStage Medical, Inc. are omitted because, considered in the aggregate, they would not constitute a significant subsidiary as of the end of the year covered by this report.

EX-23

Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the following Registration Statements:

(1) Registration Statement and related prospectus (Form S-3 Nos. 333-141808, 333-152904, and 333-170654) of NxStage Medical, Inc., and

(2) Registration Statements (Form S-8 Nos. 333-130241, 333-141804, 333-149225, 333-151857, 333-158142, 333-160109, 333-176014, and 333-196414) pertaining to the NxStage Medical, Inc. 1999 Stock Option and Grant Plan, the NxStage Medical, Inc. 2005 Stock Incentive Plan, the NxStage Medical, Inc. 2014 Omnibus Incentive Plan, and the NxStage Medical, Inc. 2005 Employee Stock Purchase Plan;

of our reports dated February 26, 2015, with respect to the consolidated financial statements of NxStage Medical, Inc. and the effectiveness of internal control over financial reporting of NxStage Medical, Inc., included in this Annual Report (Form 10-K) of NxStage Medical, Inc. for the year ended December 31, 2014.

/s/ Ernst & Young LLP

Boston, Massachusetts

February 26, 2015

EX-31.1

Exhibit 31.1

CERTIFICATION PURSUANT TO RULE 13A-14(A)/15D-14(A),

AS ADOPTED PURSUANT TO

SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Jeffrey H. Burbank, certify that:

1. I have reviewed this Annual Report on Form 10-K of NxStage Medical, Inc. for the year ended December 31, 2014 (this “report”);

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal controls over financial reporting.

/s/ Jeffrey H. Burbank

Jeffrey H. Burbank

Chief Executive Officer

Date: February 26, 2015

EX-31.2

Exhibit 31.2

CERTIFICATION PURSUANT TO RULE 13A-14(A)/15D-14(A),

AS ADOPTED PURSUANT TO

SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Matthew W. Towse, certify that:

1. I have reviewed this Annual Report on Form 10-K of NxStage Medical, Inc. for the year ended December 31, 2014 (this “report”);

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal controls over financial reporting.

/s/ Matthew W. Towse

Matthew W. Towse

Chief Financial Officer and Senior Vice President

Date: February 26, 2015

EX-32.1

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report on Form 10-K of NxStage Medical, Inc. (the “Company”) for the year ended December 31, 2014 as filed with the Securities and Exchange Commission on the date hereof (this “report”), I, Jeffrey H. Burbank, Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to my knowledge:

(1) This report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in this report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Jeffrey H. Burbank

Jeffrey H. Burbank

Chief Executive Officer

Date: February 26, 2015

EX-32.2

Exhibit 32.2

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report on Form 10-K of NxStage Medical, Inc. (the “Company”) for the year ended December 31, 2014 as filed with the Securities and Exchange Commission on the date hereof (this “report”), I, Matthew W. Towse, Chief Financial Officer and Senior Vice President of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to my knowledge:

(1) This report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in this report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ Matthew W. Towse

Matthew W. Towse

Chief Financial Officer and Senior Vice President

Date: February 26, 2015

XML

Business Combination (Tables)

12 Months Ended

Dec. 31, 2014

Business Combinations [Abstract]

Allocation of Purchase Price to Estimated Fair Value of Assets Acquired

The following table presents the allocation of the purchase price to the estimated fair value of the assets acquired (in thousands):

Assets purchased:
Inventory	$	523
Field Equipment		3,298
Customer relationships		170
Assets acquired	$	3,991

XML

Intangible Assets - Summary of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	$ 34,675	$ 34,685
Finite-Lived Intangible Assets, Accumulated Amortization	(20,305)	(17,491)
Bloodline Needle and Other Patented and Unpatented Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	6,200	6,200
Finite-Lived Intangible Assets, Accumulated Amortization	(5,619)	(4,844)
Finite-Lived Intangible Assets, Estimated Useful Life	8 years
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	2,300	2,300
Finite-Lived Intangible Assets, Accumulated Amortization	(1,191)	(1,026)
Finite-Lived Intangible Assets, Estimated Useful Life	14 years
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	26,175	26,185
Finite-Lived Intangible Assets, Accumulated Amortization	$ (13,495)	$ (11,621)
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Estimated Useful Life	8 years
Minimum [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Estimated Useful Life	10 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Estimated Useful Life	14 years
Maximum [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Estimated Useful Life	14 years

XML

Summary of Significant Accounting Policies - Schedule of Rollforward of Warranty Accrual (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Balance at Beginning of Year	$ 297	$ 324	$ 380
Provision	441	412	540
Usage	(451)	(439)	(596)
Balance at End of Year	$ 287	$ 297	$ 324

XML

Commitments and Contingencies - Future Minimum Rental Payments Under Operating Leases (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
2015	$ 4,412
2016	4,390
2017	4,244
2018	4,369
2019	3,535
Thereafter	8,523
Total	$ 29,473

XML

Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.8	$ 2.8	$ 2.8

XML

Stock Plans and Stock-Based Compensation - Summary of Status of Stock Options Granted Under All Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Beginning balance	4,825,880
Shares, granted	997,459
Shares, exercised	(1,524,601)
Shares, forfeited or expired	(196,313)
Ending balance	4,102,425
Shares, Fully vested and exercisable	2,822,955
Shares, fully vested, exercisable and expected to vest	3,956,565
Weighted average exercise price, outstanding at beginning of year	$ 10.73
Weighted average exercise price, granted	$ 14.35
Weighted average exercise price, exercised	$ 9.04
Weighted average exercise price, forfeited or expired	$ 15.17
Weighted average exercise price, outstanding at end of year	$ 12.02
Weighted average exercise price, fully vested and exercisable	$ 11.30
Weighted average exercise price, fully vested, exercisable and expected to vest	$ 11.96
Aggregate intrinsic value, outstanding at end of year	$ 24,832
Aggregate intrinsic value, fully vested and exercisable	19,264
Aggregate intrinsic value, fully vested, exercisable and expected to vest	$ 24,197
Average remaining contractual life, outstanding at end of year	5 years 2 months 5 days
Average remaining contractual life, fully vested and exercisable	3 years 8 months 23 days
Average remaining contractual life, fully vested, exercisable and expected to vest	5 years 22 days

XML

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Balance at Beginning of Year	$ 321	$ 424	$ 510
Provision (Recoveries)	219	47
Write-offs	(115)	(150)	(86)
Balance at End of Year	$ 425	$ 321	$ 424

XML

Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities (Tables)

12 Months Ended

Dec. 31, 2014

Payables and Accruals [Abstract]

Components of Accrued Expenses

The components of accrued expenses are as follows (in thousands):

	December 31,
	2014		2013
Payroll, compensation and related benefits	$	12,346	$	9,041
Distribution expenses		3,069		2,762
General and administrative expenses		3,075		2,207
Audit, legal, and consulting fees		1,394		2,725
Other		4,769		4,290
Total	$	24,653	$	21,025

Components of Other Current liabilities

The components of other current liabilities are as follows (in thousands):

	December 31,
	2014		2013
Deferred revenue, current portion	$	2,195	$	—
Capital lease obligations		2,246		1,471
Other		1,724		399
Total	$	6,165	$	1,870

Schedule of Other Long-term Liabilities

The components of other long term liabilities are as follows (in thousands):

	December 31,
	2014		2013
Capital lease obligations	$	11,876	$	14,133
Lease incentive obligations		4,569		3,589
Benefit plan obligations		1,745		1,770
Other		1,434		781
Total	$	19,624	$	20,273

XML

Stock Plans and Stock-Based Compensation - Estimated Fair Value of Options at Date of Grant (Detail) (Options to Purchase Common Stock [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)			4 years 6 months
Risk-free interest rate, Lower range	1.56%	0.75%	0.67%
Risk-free interest rate, Upper range	1.69%	1.04%	0.90%
Expected stock price volatility, Lower range	43.00%
Expected stock price volatility, Upper range	45.00%
Expected stock price volatility		62.00%	70.00%
Expected dividend yield	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	4 years 4 months 24 days	4 years 6 months
Expected dividend yield	0.00%	0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	5 years	4 years 8 months 12 days
Expected dividend yield	0.00%	0.00%

XML

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Income Tax [Line Items]
Provision for (benefit from) income taxes	$ 1,253,000	$ (245,000)	$ 1,033,000
Foreign tax expense (benefit)	(1,200,000)	(1,200,000)
Excess tax deductions related to stock-based compensation	54,200,000
Excess tax deductions related to stock-based compensation, state	27,700,000
Foreign tax credit carryforward expiration dates	Between 2018 and 2021 if not utilized
Increase in deferred tax valuation allowance	9,100,000
Gross unrecognized tax benefits	400,000	500,000	1,500,000
Interest and penalties		100,000	400,000
Federal [Member]
Schedule of Income Tax [Line Items]
Net operating loss carryforward	366,000,000
Expiry period of net operating loss carryforward	Between 2015 and 2034 if not utilized
Federal [Member] | Research [Member]
Schedule of Income Tax [Line Items]
Research and development credit carryforward	7,000,000
Expiration year of research and development tax credit carryforward	2020
State [Member]
Schedule of Income Tax [Line Items]
Net operating loss carryforward	187,000,000
Expiry period of net operating loss carryforward	Between 2015 and 2034 if not utilized
State [Member] | Research [Member]
Schedule of Income Tax [Line Items]
Research and development credit carryforward	1,900,000
Foreign [Member] | Research [Member]
Schedule of Income Tax [Line Items]
Research and development credit carryforward	$ 1,000,000

XML

Accumulated Other Comprehensive (Loss) Income - Summary of Additional Information on Accumulated Other Comprehensive (Loss) Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance net of tax	$ 212	$ 470	$ (68)
Other comprehensive loss before reclassifications	(2,662)	398	647
(Gain) Loss reclassified to earnings	258	(656)	(109)
Total other comprehensive loss	(2,404)	(258)	538
Ending balance net of tax	(2,192)	212	470
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance net of tax	335	81	(68)
Other comprehensive loss before reclassifications	(1,439)	254	149
Total other comprehensive loss	(1,439)	254	149
Ending balance net of tax	(1,104)	335	81
Unrealized Gain (Loss) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance net of tax	(123)	389
Other comprehensive loss before reclassifications	(1,223)	144	498
(Gain) Loss reclassified to earnings	258	(656)	(109)
Total other comprehensive loss	(965)	(512)	389
Ending balance net of tax	$ (1,088)	$ (123)	$ 389

XML

Net Loss per Share - Schedule of Anti-dilutive Net Loss Per Share (Detail) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share	1,112	1,165	2,719
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share	876	1,013	1,602
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share	236	152	196
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share			921

XML

Income Taxes - Changes in Unrecognized Tax Benefits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance at beginning of the year	$ 411	$ 1,067	$ 678
Increase in unrecognized tax benefits current year	88	411	389
Decrease in unrecognized tax benefits prior years	(110)
Reductions due to audit settlement	(42)	(1,067)
Balance at end of year	$ 347	$ 411	$ 1,067

XML

Business Combination - Allocation of Purchase Price to Estimated Fair Value of Assets Acquired (Detail) (Kimal PLC [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Kimal PLC [Member]
Assets purchased:
Inventory	$ 523
Field Equipment	3,298
Customer relationships	170
Assets acquired	$ 3,991

XML

Stock Plans and Stock-Based Compensation - Valuation Assumptions for ESPP (Detail) (Employee Stock Purchase Plan 2005 [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Stock Purchase Plan 2005 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in months)	6 months	6 months	6 months
Risk-free interest rate, Lower range	0.07%	0.09%	0.06%
Risk-free interest rate, Upper range	0.10%	0.12%	0.15%
Expected stock price volatility, Lower range	26.30%	20.10%	23.30%
Expected stock price volatility, Upper range	27.40%	33.60%	36.00%
Expected dividend yield	0.00%	0.00%	0.00%

XML

Derivative Instruments and Hedging - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Hedging Transactions And Derivative Financial Instruments [Line Items]
Period of cash flow hedges	12 months
Cash Flow Hedges [Member]
Hedging Transactions And Derivative Financial Instruments [Line Items]
Notional amount of outstanding contracts	12.5	$ 10.4
Fair value of outstanding contracts liability	1.3	$ 0.2

XML

Stock Plans and Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock vests over a requisite service period	3 years
Fair value of options vested	$ 4,900,000	$ 5,100,000	$ 5,100,000
Aggregate intrinsic value of options exercised	9,200,000	3,500,000	8,800,000
Share-based compensation expense	12,881,000	8,638,000	11,403,000
Weighted average period	2 years 7 months 6 days
Unrecognized stock compensation cost	19,000,000
Postemployment Benefits Liability, Noncurrent	1,745,000	1,770,000
2014 Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Stock option expiration period	10 years
Reduction in number of shares available for grant	1.62
Share available for grant	5,300,000
Number of shares authorized for grant	5,600,000
Expiration date description	Ten years from the date of grant
Employee Stock Purchase Plan 2005 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share available for grant	100,000
Number of shares authorized for grant	700,000
Offering period	6 months
Eligibility for the participation in the 2005 purchase plan	An employee becomes eligible to participate in the 2005 Purchase Plan once he or she has been employed for at least three months and is regularly employed for at least 20 hours per week for more than three months in a calendar year.
Price at which employee can purchase common stock in an offering	95 percent of the closing price of our common stock on the NASDAQ Global Select Market on the lower of the first or last day of the offering period
Price at which employee can purchase common stock in an offering percentage	95.00%
Weighted-average fair value of restricted stock granted	$ 1.46	$ 3.10	$ 4.57
Shares issued under employee stock purchase plan, Shares	70,899	75,301	56,691
Share-based compensation expense	100,000	100,000	200,000
Options to Purchase Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value of options granted	$ 5.80	$ 6.29	$ 9.23
Options to Purchase Common Stock [Member] | 2014 Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted stock	$ 3,200,000	$ 2,800,000	$ 3,700,000
Weighted-average fair value of restricted stock granted	$ 14.35	$ 11.97	$ 16.89
Restricted Stock Units (RSUs) [Member] | 2014 Omnibus Incentive Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted Stock Units (RSUs) [Member] | 2014 Omnibus Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years

XML

Income Taxes - Summary of Income (Loss) Before Income Taxes by Geography (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S.	$ (24,315)	$ (20,613)	$ (16,026)
Foreign	1,255	1,807	1,906
Net loss before income taxes	$ (23,060)	$ (18,806)	$ (14,120)

XML

Supplemental Cash Flow Information

12 Months Ended

Dec. 31, 2014

Supplemental Cash Flow Elements [Abstract]

Supplemental Cash Flow Information

19. Supplemental Cash Flow Information

The following additional information is provided with respect to the consolidated statements of cash flows (in thousands):

	Years Ended December 31,
	2014		2013		2012
Supplemental Disclosures:
Cash paid for interest	$	671	$	549	$	1,457
Cash paid for taxes		903		1,181		586
Noncash Investing and Financing Activities:
Transfers from inventory to field equipment	$	25,370	$	13,827	$	12,172
Transfers from field equipment to deferred cost of revenues		13,110		10,260		10,360
Payment of Corporate Bonus Plan in common stock		—		1,034		878
Market value of shares received in payment for exercise of stock options		3,026		412		513
Construction-in-process financed by construction liability		4,898		3,568		8,343
Settlement of debt through the issuance of common stock		—		—		45,219
Leasehold improvements paid by the landlord		—		—		4,300
Property and equipment acquired under capital lease		76		745		1,615
Acquisition of business		—		1,757		—
Increase in deferred revenues related to the new manufacturing facility in Germany		3,608		—		6,124
Deferred revenues and deferred costs related to acquiree recorded as a reduction of consideration paid		—		335		—

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Property and Equipment, Field Equipment and Deferred Cost of Revenues - Summary of Components of Property and Equipment, Net (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 94,454	$ 74,270
Less accumulated depreciation	(27,880)	(21,792)
Property and equipment, net	66,574	52,478
Manufacturing Equipment and Tooling [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	34,621	24,963
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	18,485	11,883
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,935	4,132
Molds [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,377	3,817
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,410	1,712
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,907	10,005
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,110	1,258
Construction-in-Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 14,609	$ 16,500

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Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables present assets and liabilities measured at fair value on a recurring basis and their level within the value hierarchy (in thousands):

December 31, 2014	Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)		Total Fair Value
Assets
Money market funds(1)	$	39,779	$	—	$	—	$	39,779
Liabilities
Foreign exchange forward contracts(2)	$	—	$	1,265	$	—	$	1,265

December 31, 2013	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value
Assets
Money market funds(1)	$	69,779	$	—	$	—	$	69,779
Foreign exchange forward contracts(2)		—		34		—		34
Liabilities
Foreign exchange forward contracts(2)	$	—	$	192	$	—	$	192
Contingent consideration liability(3)		—		—		540		540

(1) Money market funds are included within cash and cash equivalents.

(2) Foreign exchange forward contracts are included within prepaid expenses and other current assets or other current liabilities depending on the gain (loss) position.

(3) Net present value of expected payments under contingent consideration liability are reported in accrued expenses.

Roll Forward of Contingent Consideration Liability Classified as Level 3 within Value Hierarchy

The following table presents the rollforward of the contingent consideration liability classified as Level 3 within the value hierarchy (in thousands):

Balance at December 31, 2013	$	540
Less Payments made		(540	)
Balance at December 31, 2014	$	—

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Income Taxes - Deferred Tax Assets (Liabilities) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Net operating loss carryforwards	$ 114,131	$ 108,772
Tax credits	10,078	9,464
Stock-based compensation	6,259	5,713
Capitalized research and development	3,120	3,677
Financing liabilities	6,281	5,007
Other	6,092	2,199
Total deferred tax assets	145,961	134,832
Deferred tax liabilities:
Fixed assets	(7,719)	(5,079)
Intangible assets	(5,326)	(6,509)
Other	(608)
Total deferred tax liabilities	(13,653)	(11,588)
Net deferred tax assets before valuation allowance	132,308	123,244
Less valuation allowance	(131,453)	(122,353)
Net deferred tax assets	$ 855	$ 891

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Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Summary of Income (Loss) Before Income Taxes by Geography

The following is a summary of income (loss) before income taxes by geography (in thousands):

	Years Ended December 31,
	2014			2013			2012
U.S.	$	(24,315	)	$	(20,613	)	$	(16,026	)
Foreign		1,255			1,807			1,906
Total	$	(23,060	)	$	(18,806	)	$	(14,120	)

Components of Provision for (Benefit from) Income Taxes

The components of the provision for (benefit from) income taxes are as follows (in thousands):

	Years Ended December 31,
	2014			2013			2012
Current:
U.S. - State	$	57		$	47		$	52
Foreign		1,278			(76	)		1,357
Total Current		1,335			(29	)		1,409
Deferred:
Foreign		(82	)		(216	)		(376	)
Total Deferred		(82	)		(216	)		(376	)
Total Provision (Benefit)	$	1,253		$	(245	)	$	1,033

Reconciliation of U.S. Federal Statutory Tax Rate to Effective Tax Rate

A reconciliation of the U.S. federal statutory tax rate to the effective tax rate is as follows:

	Years Ended December 31,
	2014			2013			2012
Federal statutory rate		34.0	%		34.0	%		34.0	%
Stock compensation		2.0	%		(2.5	)%		(5.6	)%
State income tax, net of federal tax benefit		1.9	%		3.2	%		2.0	%
U.S. research credits		4.1	%		11.7	%		3.3	%
Foreign income inclusion in the U.S.		(2.8	)%		(6.7	)%		(3.1	)%
Valuation allowance		(39.7	)%		(40.2	)%		(31.4	)%
Change in tax reserves		—	%		4.0	%		(5.6	)%
Other, net		(4.9	)%		(2.2	)%		(0.9	)%
Effective tax rate		(5.4	)%		1.3	%		(7.3	)%

Deferred Tax Assets (Liabilities)

Deferred income tax assets and liabilities reflect the tax effects of differences in the recognition of income and expense items for tax and financial reporting purposes. Deferred tax assets (liabilities), the majority of which are non-current, are made up of the following (in thousands):

	December 31,
	2014			2013
Deferred tax assets:
Net operating loss carryforwards	$	114,131		$	108,772
Tax credits		10,078			9,464
Stock-based compensation		6,259			5,713
Capitalized research and development		3,120			3,677
Financing liabilities		6,281			5,007
Other		6,092			2,199
Total deferred tax assets		145,961			134,832
Deferred tax liabilities:
Fixed assets		(7,719	)		(5,079	)
Intangible assets		(5,326	)		(6,509	)
Other		(608	)		—
Total deferred tax liabilities		(13,653	)		(11,588	)
Net deferred tax assets before valuation allowance		132,308			123,244
Less valuation allowance		(131,453	)		(122,353	)
Net deferred tax assets	$	855		$	891

Changes in Unrecognized Tax Benefits

The below table details the changes in unrecognized tax benefits, which if recognized would favorably impact our effective tax rate (in thousands):

	Years Ended December 31,
	2014			2013			2012
Balance at beginning of the year	$	411		$	1,067		$	678
Increase in unrecognized tax benefits current year		88			411			389
Decrease in unrecognized tax benefits prior years		(110	)		—			—
Reductions due to audit settlement		(42	)		(1,067	)		—
Balance at end of year	$	347		$	411		$	1,067

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Property and Equipment, Field Equipment and Deferred Cost of Revenues - Components of Assets Subject to Capital Leases (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Less accumulated depreciation	$ (2,905)
Assets subject to capital leases, net	22,283
Manufacturing Facility [Member] | Germany [Member]
Property, Plant and Equipment [Line Items]
Manufacturing facility in Germany/Other assets subject to capital leases	22,750
Assets Held under Capital Leases [Member]
Property, Plant and Equipment [Line Items]
Manufacturing facility in Germany/Other assets subject to capital leases	$ 2,438

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Business Segment and Geographic Information - Total Long-Lived Tangible Assets by Geographic Area (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	$ 87,692	$ 65,519	$ 46,421
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	45,501	26,082	20,967
Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	12,689	10,578	3,949
Other Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	482	94
Total Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	58,672	36,754	24,916
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	21,246	20,235	17,058
Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	7,774	8,530	4,447
Total Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-Lived Assets	$ 29,020	$ 28,765	$ 21,505

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Debt and Capital Lease Obligations - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jun. 10, 2014	May 31, 2013
Debt Instrument [Line Items]
Current portion of long-term debt	$ 93,000	$ 102,000
Revolving line of credit	35,000,000
Outstanding borrowings under revolving line of credit	0
Credit commitment available for borrowing	28,000,000
Silicon Valley Bank [Member]
Debt Instrument [Line Items]
Revolving line of credit	15,000,000
Revolving line of credit expiration date	Mar. 31, 2014
General Electric Capital Corporation [Member]
Debt Instrument [Line Items]
Revolving line of credit expiration date	Jun. 30, 2019
Maximum amount borrowed under new revolving line of credit			35,000,000
Line of credit facility interest rate description	(1) a LIBOR rate plus 2.5% or (2) a base rate plus 1.5%, where the base rate is the highest of (a) the Prime Rate, (b) the Federal Funds Rate plus 0.5% and (c) a LIBOR rate plus 1%, at our election
Mortgage One [Member]
Debt Instrument [Line Items]
Current portion of long-term debt				600,000
Interest rate on mortgage loan	6.00%
Mortgage Loan Period	10 years
Frequency of periodic payments	Payable quarterly over a 10 year period
Mortgage Two [Member]
Debt Instrument [Line Items]
Current portion of long-term debt				$ 500,000
Interest rate on mortgage loan	2.00%
Mortgage Loan Period	10 years
Frequency of periodic payments	Payable biannually over a 10 year period

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Summary of Significant Accounting Policies - Estimated Useful Lives of Property and Equipment and Field Equipment (Detail)	12 Months Ended
	Dec. 31, 2014
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Leasehold improvements	Lesser of the lease term (including any renewal periods if appropriate) or estimated useful life of the asset
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	30 years
Manufacturing Equipment and Tooling [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	3 years
Manufacturing Equipment and Tooling [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	12 years
Computer and Office Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	3 years
Computer and Office Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	5 years
Molds [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	5 years
Molds [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	7 years
Furniture [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	5 years
Furniture [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	7 years
Field Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	5 years
Field Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Life	7 years

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Inventory

12 Months Ended

Dec. 31, 2014

Inventory Disclosure [Abstract]

Inventory

3. Inventory

Inventory includes material, labor and overhead. The components of inventory are as follows (in thousands):

	December 31,
	2014		2013
Purchased components	$	19,238	$	15,946
Work in process		9,981		10,762
Finished goods		16,182		11,093
	$	45,401	$	37,801

XML

Debt and Capital Lease Obligations - Schedule of Future Minimum Payments Under Capital Leases (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Debt Disclosure [Abstract]
2015	$ 2,326
2016	2,312
2017	1,925
2018	1,506
2019	851
Thereafter	9,065
Total minimum lease payments	17,985
Less amount representing interest	(3,863)
Present value of future minimum lease payments	$ 14,122

XML

Supplemental Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2014

Supplemental Cash Flow Elements [Abstract]

Summary of Supplemental Cash Flow Information

The following additional information is provided with respect to the consolidated statements of cash flows (in thousands):

	Years Ended December 31,
	2014		2013		2012
Supplemental Disclosures:
Cash paid for interest	$	671	$	549	$	1,457
Cash paid for taxes		903		1,181		586
Noncash Investing and Financing Activities:
Transfers from inventory to field equipment	$	25,370	$	13,827	$	12,172
Transfers from field equipment to deferred cost of revenues		13,110		10,260		10,360
Payment of Corporate Bonus Plan in common stock		—		1,034		878
Market value of shares received in payment for exercise of stock options		3,026		412		513
Construction-in-process financed by construction liability		4,898		3,568		8,343
Settlement of debt through the issuance of common stock		—		—		45,219
Leasehold improvements paid by the landlord		—		—		4,300
Property and equipment acquired under capital lease		76		745		1,615
Acquisition of business		—		1,757		—
Increase in deferred revenues related to the new manufacturing facility in Germany		3,608		—		6,124
Deferred revenues and deferred costs related to acquiree recorded as a reduction of consideration paid		—		335		—

XML

Inventory (Tables)

12 Months Ended

Dec. 31, 2014

Inventory Disclosure [Abstract]

Components of Inventory

The components of inventory are as follows (in thousands):

	December 31,
	2014		2013
Purchased components	$	19,238	$	15,946
Work in process		9,981		10,762
Finished goods		16,182		11,093
	$	45,401	$	37,801

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Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Allowance for Doubtful Accounts

Activity related to allowance for doubtful accounts consisted of the following (in thousands):

Year Ended	Balance at Beginning of Year		Provision (Recoveries)		Write-offs			Balance at End of Year
December 31, 2014	$	321	$	219	$	(115	)	$	425
December 31, 2013	$	424	$	47	$	(150	)	$	321
December 31, 2012	$	510	$	—	$	(86	)	$	424

Estimated Useful Lives of Property and Equipment and Field Equipment

The estimated useful lives of property and equipment and field equipment are as follows:

	Estimated Useful Life
Buildings	30 years
Manufacturing equipment and tooling	3 to 12 years
Leasehold improvements	Lesser of the lease term (including any renewal periods if appropriate) or estimated useful life of the asset
Computer and office equipment	3 to 5 years
Molds	5 to 7 years
Furniture	5 to 7 years
Field equipment	5 to 7 years

Schedule of Rollforward of Warranty Accrual

The following is a rollforward of our warranty accrual (in thousands):

Year Ended	Balance at Beginning of Year		Provision		Usage			Balance at End of Year
December 31, 2014	$	297	$	441	$	(451	)	$	287
December 31, 2013	$	324	$	412	$	(439	)	$	297
December 31, 2012	$	380	$	540	$	(596	)	$	324

XML

Intangible Assets - Estimated Aggregated Amortization Expense for Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
2015	$ 2,621
2016	2,040
2017	2,040
2018	2,040
2019	2,040
Thereafter	3,589
Total	$ 14,370	$ 17,194

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Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

The following table sets forth selected quarterly information (unaudited) (in thousands, except per share data):

	Three Months Ended
	March 31, 2014			June 30, 2014			September 30, 2014			December 31, 2014
Revenues	$	72,221		$	74,083		$	75,286		$	79,911
Gross profit		28,934			27,530			28,587			30,852
Loss from operations		(4,789	)		(6,651	)		(6,274	)		(4,473	)
Net loss attributable to stockholders of NxStage Medical, Inc.		(5,275	)		(7,113	)		(6,706	)		(4,852	)
Net loss per share, basic and diluted	$	(0.09	)	$	(0.12	)	$	(0.11	)	$	(0.08	)

	Three Months Ended
	March 31, 2013			June 30, 2013			September 30, 2013			December 31, 2013
Revenues	$	61,644		$	65,462		$	66,873		$	69,450
Gross profit		24,000			25,087			25,528			27,888
Loss from operations		(4,536	)		(4,271	)		(4,413	)		(4,578	)
Net loss attributable to stockholders of NxStage Medical, Inc.		(4,994	)		(3,405	)		(4,986	)		(5,176	)
Net loss per share, basic and diluted	$	(0.08	)	$	(0.06	)	$	(0.08	)	$	(0.08	)

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Property and Equipment, Field Equipment and Deferred Cost of Revenues (Tables)

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Summary of Components of Property and Equipment, Net

The components of property and equipment, net are as follows (in thousands):

	December 31,
	2014			2013
Manufacturing equipment and tooling	$	34,621		$	24,963
Leasehold improvements		18,485			11,883
Computer and office equipment		8,935			4,132
Molds		5,377			3,817
Furniture		2,410			1,712
Buildings		8,907			10,005
Land		1,110			1,258
Construction-in-process		14,609			16,500
		94,454			74,270
Less accumulated depreciation		(27,880	)		(21,792	)
Property and equipment, net	$	66,574		$	52,478

Components of Assets Subject to Capital Leases

Our property and equipment includes the following amounts for assets subject to capital leases (amounts in thousands):

	December 31, 2014
Manufacturing facility in Germany	$	22,750
Other assets subject to capital leases		2,438
Less accumulated depreciation		(2,905	)
Assets subject to capital leases, net	$	22,283

Components of Field Equipment, Net

The components of field equipment, net are as follows (in thousands):

	December 31,
	2014			2013
Field equipment	$	61,132		$	49,695
Less accumulated depreciation		(40,014	)		(36,654	)
Field equipment, net	$	21,118		$	13,041

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Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Intangible Assets

The components of intangible assets, net are as follows (in thousands):

	December 31, 2014					December 31, 2013					Estimated Useful Life
	Cost		Accumulated Amortization			Cost		Accumulated Amortization
Bloodline, needle and other patented and unpatented technology	$	6,200	$	(5,619	)	$	6,200	$	(4,844	)		8 years
Trade names		2,300		(1,191	)		2,300		(1,026	)		14 years
Customer relationships		26,175		(13,495	)		26,185		(11,621	)		10/14 years
Intangible assets, net	$	34,675	$	(20,305	)	$	34,685	$	(17,491	)

Estimated Future Aggregated Amortization Expense for Intangible Assets

The estimated future aggregated amortization expense for intangible assets as of December 31, 2014 is as follows (in thousands):

2015	$	2,621
2016		2,040
2017		2,040
2018		2,040
2019		2,040
Thereafter		3,589
	$	14,370

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Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Principles of Consolidation and Basis of Presentation

The accompanying consolidated financial statements include the accounts of NxStage Medical, Inc. and our wholly-owned and majority-owned subsidiaries. All material intercompany transactions and balances have been eliminated in consolidation.

Use of Estimates

The preparation of our consolidated financial statements in conformity with GAAP requires our management to make estimates and assumptions that affect reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Revenue Recognition

We recognize revenue from product sales and services when earned. Revenues are recognized when: (a) there is persuasive evidence of an arrangement, (b) the product has been shipped or services and supplies have been provided to the customer, (c) the sales price is fixed or determinable and (d) collection is reasonably assured.

Certain agreements with distributors allow for product returns and credits. For shipment of product sold to distributors, revenue is recognized at the time of sale if a reasonable estimate of future returns or credit can be made. If a reasonable estimate of future returns or credit cannot be made, we recognize revenue using the “sell-through” method. Under the “sell-through” method, revenue and related costs of revenue is deferred until the final resale of such products to end customers.

In addition to contractually determined volume discounts, in many agreements we offer rebates based on sales to specific end customers and discounts for early payment. Rebates and discounts are recorded as a reduction of sales and trade accounts receivable, based on our best estimate of the amount of probable future rebate or discount on current sales.

We enter into multiple-element arrangements that may include a combination of equipment, related disposables and services. Revenue arrangements with multiple elements are divided into separate units of accounting if specified criteria are met, including whether the delivered element has stand-alone value to the customer, the consideration received is allocated among the separate units based on their respective selling price, and the applicable revenue recognition criteria are applied to each of the separate units.

We determine selling price using vendor specific objective evidence (“VSOE”), if it exists, otherwise third-party evidence of selling price is used. If neither VSOE nor third-party evidence of selling price exists for a unit of accounting, we use best estimated selling price (“BESP”). We generally expect that we will not be able to establish third-party evidence due to the nature of our products and the markets in which we compete, and, as such, we typically will determine selling price using VSOE or BESP.

We determine BESP for an individual element based on consideration of both market and Company-specific factors, including the selling price and profit margin for similar products, the cost to produce the deliverable and the anticipated margin on that deliverable and the characteristics of the varying markets in which the deliverable is sold.

System One Segment

We derive revenue in the home market from the sales of hemodialysis therapy to customers in which the customer either purchases or rents the System One and/or PureFlow SL hardware and purchases a specified number of disposable products and service.

For customers that purchase the System One and PureFlow SL hardware, in the U.S. home market, due to the depot service model whereby equipment requiring service is picked up and a replacement device is shipped to the site of care, we recognize fees received from equipment sale as revenue on a straight-line basis over the expected term of our remaining service obligation and direct costs relating to the delivered equipment are deferred and amortized over the same expected period as the related revenue. Disposable products revenue is recognized on a monthly basis upon delivery.

Under the rental arrangements, revenue is recognized on a monthly basis in accordance with agreed upon contract terms and pursuant to binding customer purchase orders and fixed payment terms.

Our sales arrangements with our international distributors are structured as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms.

In the critical care market, we structure sales of the System One and disposable products as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Certain of these arrangements provide for training, technical support and extended warranty services to our customers. We recognize training and technical support revenue when the related services are performed. In the case of extended warranty, the service revenue is recognized ratably over the extended warranty period.

In-Center Segment

Our In-Center segment sales are structured as direct product sales primarily through distributors, and we have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Some of our distribution contracts for the In-Center segment contain minimum volume commitments with negotiated pricing discounts at different volume tiers. Each agreement may be canceled upon a material breach, subject to certain curing rights, and in many instances minimum volume commitments can be reduced or eliminated upon certain events.

Services Segment

Revenues in our Services segment are derived from dialysis care services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

Revenues are recognized based on a customary fee schedule, net of estimated contractual allowances to reflect the estimated amounts to be received from the payor. Revenues are recognized in the period in which services are provided when we have the ability to reasonably estimate amounts ultimately collectible from the payor. In instances where we do not have the ability to reasonably estimate amounts ultimately collectible, as is often the case with non-contracted commercial health plans and amounts due from patients (including co-pay and deductible amounts), revenue is recognized in the period in which cash is received.

Foreign Currency Translation and Transactions

Assets and liabilities of our foreign operations are translated into U.S. dollars at current exchange rates, and income and expense items are translated at average rates of exchange prevailing during the year. Foreign exchange gains and (losses) on intercompany loans considered permanent investments are recorded in other comprehensive loss. Gains and (losses) realized from transactions denominated in foreign currencies, including intercompany balances not considered permanent investments, are included in the consolidated statements of comprehensive loss within other (expense) income, net.

Cash and Cash Equivalents

We consider all highly-liquid investments purchased with original maturities of 90 days or less to be cash equivalents. Cash equivalents include amounts invested in treasury obligation money market funds. Cash equivalents are stated at cost plus accrued interest, which approximates market value.

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk consist principally of cash equivalents, derivatives and accounts receivable. To mitigate such risk, with respect to cash and cash equivalents, we place our cash in bank deposit accounts with financial institutions that have investment grade ratings and capital ratios exceeding minimum Federal Reserve Adequacy Guidelines and in treasury obligation money market funds. To mitigate concentration of credit risk with respect to derivatives we enter into transactions with highly-rated financial institutions and frequently monitor the credit worthiness of our counterparties.

Concentration of credit risk with respect to accounts receivable is primarily limited to certain customers to whom we make substantial sales. Two customers represented 18% and 16% of accounts receivable at December 31, 2014 and one customer represented 19% of accounts receivable at December 31, 2013. To reduce risk, we routinely assess the financial strength of our customers and closely monitor their amounts due and, as a result of our assessment, believe that our accounts receivable credit risk exposure is limited. Historically, we have not experienced any significant credit losses related to an individual customer or group of customers in any particular market or geographic area. We maintain an allowance for doubtful accounts based on an analysis of historical losses from uncollectible accounts, aging of unpaid accounts receivable balances and risks identified for specific customers who may not be able to make required payments. Provisions for the allowance for doubtful accounts are recorded in general and administrative expenses in the accompanying consolidated statements of comprehensive loss.

Activity related to allowance for doubtful accounts consisted of the following (in thousands):

Year Ended	Balance at Beginning of Year		Provision (Recoveries)		Write-offs			Balance at End of Year
December 31, 2014	$	321	$	219	$	(115	)	$	425
December 31, 2013	$	424	$	47	$	(150	)	$	321
December 31, 2012	$	510	$	—	$	(86	)	$	424

We use and are dependent upon a number of single source suppliers of raw materials, components, finished goods and sterilization services. We are dependent on the ability of our suppliers to provide products on a timely basis and on favorable pricing terms. The loss of certain principal suppliers or a significant reduction in product availability from principal suppliers would have a material adverse effect on us, at least in the near term. We believe that our relationships with our suppliers are satisfactory.

Fair Value Measures

Certain financial and non financial assets and liabilities recorded at fair value have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standard. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable such as quoted prices, interest rates and yield curves for similar instruments and model-derived valuations whose inputs are observable. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability.

Derivative Instruments and Hedging

Derivative instruments, namely our foreign exchange forward contracts, are recognized on the balance sheet at fair value at the balance sheet date. Changes in the fair value of derivatives that are designated and highly effective as cash flow hedges are deferred in accumulated other comprehensive income (loss) and subsequently recognized in cost of revenues in the same period the hedged items are recognized. The ineffective portion of derivative instruments designated as cash flow hedges, are recorded in other income (expense), net. If the underlying forecasted transaction does not occur, or it becomes probable that it will not occur, the gains and losses on the related derivative instrument are recognized in earnings and any related gains and losses recorded in other comprehensive income (loss) are reclassified into earnings.

Inventory

Inventory is stated at the lower of cost, determined using the first-in first-out method (FIFO), or market (net realizable value). We record a provision for any excess or obsolete inventory when warranted based on remaining shelf-life and estimated future demand. We also review our inventory value to determine if it reflects the lower of cost or market based on factors such as inventory items sold at negative gross margins and purchase commitments.

Property and Equipment and Field Equipment

Property and equipment and field equipment are recorded at cost less accumulated depreciation. Depreciation is provided over the estimated useful lives of the related assets using the straight-line method for financial statement purposes. The estimated useful life of our assets are periodically reviewed for reasonableness. Changes in useful lives are accounted for prospectively. Repairs and maintenance are expensed as incurred. When property and equipment are retired, sold or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in operations. When field equipment is sold, the asset’s carrying amount and related accumulated depreciation is removed from the accounts and any gain or loss is deferred and recognized in operations on a straight-line basis over the same period as the related revenues.

We capitalize certain costs, including internal payroll and external direct project costs, incurred in connection with developing or obtaining software designated for internal use. These costs are included in property and equipment and are amortized over the estimated useful lives of the related software.

Construction-in-process is stated at cost, which includes the cost of construction and other direct costs attributable to the construction. No provision for depreciation is made on construction-in-process until such time as the relevant assets are completed and put into use. Construction-in-process at December 31, 2014 and 2013 primarily represents the costs of building, machinery, equipment under installation and software and computer costs.

Field equipment consists of equipment being utilized under disposable-based rental agreements as well as “service pool” equipment. Service pool equipment is equipment owned and maintained by us that are swapped for equipment that need repairs or maintenance by us while being rented or owned by a customer. We record a provision for any excess, lost or damaged equipment when warranted based on an assessment of the equipment in the service pool. Write-downs for equipment are included in distribution expenses.

The estimated useful lives of property and equipment and field equipment are as follows:

	Estimated Useful Life
Buildings	30 years
Manufacturing equipment and tooling	3 to 12 years
Leasehold improvements	Lesser of the lease term (including any renewal periods if appropriate) or estimated useful life of the asset
Computer and office equipment	3 to 5 years
Molds	5 to 7 years
Furniture	5 to 7 years
Field equipment	5 to 7 years

Intangibles and Other Long-Lived Assets

Intangible assets are carried at cost less accumulated amortization. For assets with determinable useful lives, amortization is computed using the straight-line method over the estimated economic lives of the respective intangible assets, ranging from eight to fourteen years. Long-lived assets, including intangible assets, are tested for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. The amount of impairment, if any, is measured based on fair value, which is determined using estimated discounted cash flows to be generated from such assets or group of assets. During 2014, 2013 and 2012, no such impairment was recognized. Assets to be disposed of are reported at the lower of the carrying amount or fair value less selling costs.

Goodwill

Goodwill represents the excess of the cost of an acquired business over the fair value of the related net assets at the date of acquisition. We test goodwill at least annually for impairment, or more frequently when events or changes in circumstances indicate that the goodwill might be impaired. This impairment test is performed annually during the fourth quarter. This test includes first a qualitative assessment and then, if necessary, a quantitative assessment to determine if the fair value of a reporting unit is less than its carrying amount. Factors considered in the qualitative assessment include, but are not limited to, both macroeconomic conditions and entity-specific conditions. For the quantitative assessment the reporting unit’s fair value is estimated using a discounted cash flow or other fair value measurement. Our reporting units with goodwill are our System One and In-center operating segments. During both 2014 and 2012, we utilized the qualitative assessment and concluded that it was more likely than not that the fair value of our reporting units was greater than their carrying value. During 2013, we utilized the quantitative assessment and concluded the fair value of the reporting units exceeds their carrying value, indicating that goodwill was not impaired. We estimated the fair value of our reporting units using a discounted cash flow approach which involves significant judgment with respect to future revenue growth, operating income, capital expenditures, changes in working capital use and the selection of a discount rate.

Stock-Based Compensation

Stock-based compensation expense is estimated as of the grant date based on the fair value of the award. We use the Black-Scholes option pricing model to estimate the fair value of stock options and quoted market prices of our common stock to estimate fair value of restricted stock. The expected term is estimated based on the contractual term of each grant and takes into account the historical experience and relevant factors concerning expected exercise and termination behavior of participants. The risk free interest rate for each grant is equal to the U.S. Treasury rate in effect at the time of grant for instruments with an expected life similar to the expected term. The stock volatility assumption is based solely on our historical volatility over the expected term of the award. The dividend yield of zero is based upon the fact that we have not historically granted cash dividends, and do not expect to issue dividends in the foreseeable future.

We recognize stock-based compensation expense over the requisite service period, which generally equals the vesting period, net of forfeitures. Forfeiture rates are estimated based on historical pre-vesting forfeiture history and are updated on a quarterly basis to reflect actual forfeitures of unvested awards and other known events. For awards that vest based on employment, we recognize the associated compensation expense on a straight-line basis. For performance based awards, we recognize expense using the graded vesting methodology based on the number of shares expected to vest. Compensation expense associated with these performance based awards is adjusted quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date the results are determined.

Warranty Costs

We accrue estimated costs that we may incur under our product warranty programs at the time the product revenue is recognized, based on contractual rights and historical experience. Warranty expense is included in cost of revenues in the consolidated statements of comprehensive loss. The following is a rollforward of our warranty accrual (in thousands):

Year Ended	Balance at Beginning of Year		Provision		Usage			Balance at End of Year
December 31, 2014	$	297	$	441	$	(451	)	$	287
December 31, 2013	$	324	$	412	$	(439	)	$	297
December 31, 2012	$	380	$	540	$	(596	)	$	324

Distribution Expenses

Distribution expenses are charged to operations as incurred and consist of costs incurred in shipping product to and from customers and the cost of any equipment lost or damaged in the distribution process. Shipping and handling costs billed to customers are included in revenues.

Research and Development Costs

Research and development costs are charged to operations as incurred.

Income Taxes

We record the tax effect of transactions when such transactions are recorded in our consolidated statement of comprehensive loss. We record a deferred tax asset or liability based on the difference between the financial statement and tax basis of assets and liabilities, as measured by the enacted tax rates. Our provision for income taxes represents the amount of taxes currently payable, if any, plus the change in the amount of net deferred tax assets or liabilities. A valuation allowance is provided against net deferred tax assets if recoverability is uncertain on a more likely than not basis.

We periodically assess our exposures related to our provisions for income taxes and accrue for contingencies that may result in potential tax obligations. For those positions where it is more likely than not that a tax benefit will be sustained, we record the largest amount of tax benefit with a greater than 50 percent likelihood of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the financial statements. We recognize interest and penalties for uncertain tax positions in income tax expense.

We conduct business globally and file income tax returns in the U.S. federal jurisdiction, various states and foreign jurisdictions. We have accumulated significant losses since our inception in 1998. Utilization of the net operating losses may be subject to limitations and certain tax years in the respective tax jurisdictions remain open to examination.

Subsequent Events

Events occurring subsequent to December 31, 2014 have been evaluated for potential recognition or disclosure in the consolidated financial statements.

Recent Accounting Pronouncements

Effective January 1, 2014, we adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists,” which impacts the presentation of unrecognized tax benefits on the statement of financial position. As a result, unrecognized tax benefits are presented as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. To the extent the tax benefit is not available at the reporting date under the governing tax law or if we do not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit is presented as a liability and not combined with deferred tax assets. The adoption of this standard did not impact our condensed consolidated financial statements, as our practice was consistent with this standard prior to its effective date.

In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers,” which provides guidance for revenue recognition. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. Early application is not permitted. We are currently assessing the potential impact the adoption of this standard will have on our financial statements.

In August 2014, the FASB issued ASU No. 2014-15, “Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern” (“ASU 2014-15”), which expands upon principles that are currently in U.S. auditing standards by providing guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and by providing related footnote disclosure requirements. The new guidance is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early adoption is permitted. We are currently evaluating the impact of this update but it is not expected to have a material impact on our financial statement disclosures.

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Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Schedule of Anti-dilutive Net Loss Per Share

The following potential common stock equivalents, as calculated using the treasury stock method, were not included in the computation of diluted net loss per share as their effect would have been anti-dilutive due to the net loss incurred (in thousands):

	Years Ended December 31,
	2014		2013		2012
Options to purchase common stock		876		1,013		1,602
Unvested restricted stock		236		152		196
Warrants to purchase common stock		—		—		921
Total		1,112		1,165		2,719

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Employee Benefit Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Percentage contribution by participant to the 401(k) Plan, maximum	75.00%
Employer Contribution of First Specific Employee Contribution Percentage	100.00%
Employee Contribution Used to Determine Employer First Contribution	3.00%
Employer Contribution of Next Specific Employee Contribution Percentage	50.00%
Employee Contribution Used to Determine Employer Next Contribution	2.00%
Company's contribution	100% of the first 3% of the employee's contribution and 50% of the next 2% of the employee's contribution
Company's contribution cost recognized	$ 1.7	$ 1.5	$ 1.3

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Derivative Instruments and Hedging (Tables)

12 Months Ended

Dec. 31, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Effect of Contracts Designated as Cash Flow Hedges on Consolidated Financial Statements

The following table presents the effect of these contracts designated as cash flow hedges on our consolidated financial statements (in thousands):

	Gain (Loss) Recognized in OCI (Effective Portion)			Gain (Loss) Reclassified from OCI into Income (Effective Portion)			Classification within the Condensed Consolidated Statement of Comprehensive Loss
Year Ended December 31, 2014	$	(1,223	)	$	(258	)	Cost of revenues
Year Ended December 31, 2013	$	144		$	656		Cost of revenues
Year Ended December 31, 2012	$	498		$	109		Cost of revenues

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Property and Equipment, Field Equipment and Deferred Cost of Revenues - Components of Field Equipment, Net (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Field equipment, net	$ 21,118	$ 13,041
Field Equipment [Member]
Property, Plant and Equipment [Line Items]
Field equipment	61,132	49,695
Less accumulated depreciation	(40,014)	(36,654)
Field equipment, net	$ 21,118	$ 13,041

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Income Taxes - Components of Provision for (Benefit from) Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
U.S. - State	$ 57	$ 47	$ 52
Foreign	1,278	(76)	1,357
Total Current	1,335	(29)	1,409
Deferred:
Foreign	(82)	(216)	(376)
Total Deferred	(82)	(216)	(376)
Total Provision (Benefit)	$ 1,253	$ (245)	$ 1,033

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Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 52,884	$ 84,134
Accounts receivable, net	24,099	20,158
Inventory	45,401	37,801
Prepaid expenses and other current assets	6,767	4,027
Total current assets	129,151	146,120
Property and equipment, net	66,574	52,478
Field equipment, net	21,118	13,041
Deferred cost of revenues	34,039	34,730
Intangible assets, net	14,370	17,194
Goodwill	41,817	41,817
Other assets	2,657	1,582
Total assets	309,726	306,962
Current liabilities:
Accounts payable	13,845	14,610
Accrued expenses	24,653	21,025
Current portion of long-term debt	93	102
Other current liabilities	6,165	1,870
Total current liabilities	44,756	37,607
Deferred revenues	52,943	53,277
Long-term debt	848	1,044
Other long-term liabilities	19,624	20,273
Total liabilities	118,171	112,201
Commitments and contingencies (Note 10)
Stockholders' equity:
Undesignated preferred stock: par value $0.001, 5,000,000 shares authorized; no shares issued and outstanding as of December 31, 2014 and 2013
Common stock: par value $0.001, 100,000,000 shares authorized; 63,429,005 and 61,666,048 shares issued as of December 31, 2014 and 2013, respectively	63	61
Additional paid-in capital	593,073	567,468
Accumulated deficit	(387,488)	(363,542)
Accumulated other comprehensive (loss) income	(2,192)	212
Treasury stock, at cost: 772,273 and 575,895 shares as of December 31, 2014 and 2013, respectively	(12,989)	(9,963)
Total NxStage Medical, Inc. stockholders' equity	190,467	194,236
Noncontrolling interest	1,088	525
Total stockholders' equity	191,555	194,761
Total liabilities and stockholders' equity	$ 309,726	$ 306,962

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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Line Items]
Impairment charges	$ 0	$ 0	$ 0
Goodwill impairment	0	0	0
Cash dividend	$ 0
Percentage of tax benefit realized upon ultimate settlement with taxing authority	50.00%
Minimum [Member]
Accounting Policies [Line Items]
Finite-Lived Intangible Assets, Estimated Useful Life	8 years
Maximum [Member]
Accounting Policies [Line Items]
Finite-Lived Intangible Assets, Estimated Useful Life	14 years
Major Customer One [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounting Policies [Line Items]
Percentage of accounts receivable	18.00%	19.00%
Major Customer Two [Member] | Customer Concentration Risk [Member] | Accounts Receivable [Member]
Accounting Policies [Line Items]
Percentage of accounts receivable	16.00%

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Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	$ (24,313)	$ (18,561)	$ (15,153)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	27,697	24,848	23,673
Stock-based compensation	12,881	8,638	11,403
Other	1,877	2,628	3,517
Changes in operating assets and liabilities:
Accounts receivable	(4,188)	(1,095)	(3,141)
Inventory	(35,063)	(20,076)	(14,545)
Prepaid expenses and other assets	(2,214)	(484)	(1,623)
Accounts payable	(212)	(2,233)	839
Accrued expenses and other liabilities	4,235	1,081	5,263
Deferred revenues	(973)	(4,887)	(3,992)
Net cash (used in) provided by operating activities	(20,273)	(10,141)	6,241
Cash flows from investing activities:
Cash paid for acquisition		(2,234)
Purchases of property and equipment	(20,097)	(16,246)	(7,694)
Net cash used in investing activities	(20,097)	(18,480)	(7,694)
Cash flows from financing activities:
Proceeds from exercise of stock options and warrants and employee stock purchase plans	11,133	5,484	5,248
Investment by noncontrolling interest holder	930	525
Purchase of treasury stock			(522)
Proceeds from loans and lines of credit		1,136
Repayments on loans and lines of credit	(98)	(38)
Payments on capital leases	(1,448)	(1,352)
Debt issuance costs	(1,056)
Net cash provided by financing activities	9,461	5,755	4,726
Foreign exchange effect on cash and cash equivalents	(341)	561	257
(Decrease) increase in cash and cash equivalents	(31,250)	(22,305)	3,530
Cash and cash equivalents, beginning of year	84,134	106,439	102,909
Cash and cash equivalents, end of year	$ 52,884	$ 84,134	$ 106,439

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Quarterly Financial Data (Unaudited) - Quarterly Financial Data (Unaudited) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 79,911	$ 75,286	$ 74,083	$ 72,221	$ 69,450	$ 66,873	$ 65,462	$ 61,644	$ 301,501	$ 263,429	$ 242,132
Gross profit	30,852	28,587	27,530	28,934	27,888	25,528	25,087	24,000	115,903	102,503	92,808
Loss from operations	(4,473)	(6,274)	(6,651)	(4,789)	(4,578)	(4,413)	(4,271)	(4,536)	(22,187)	(17,798)	(11,206)
Net loss attributable to stockholders of NxStage Medical, Inc.	$ (4,852)	$ (6,706)	$ (7,113)	$ (5,275)	$ (5,176)	$ (4,986)	$ (3,405)	$ (4,994)	$ (23,946)	$ (18,561)	$ (15,153)
Net loss per share, basic and diluted	$ (0.08)	$ (0.11)	$ (0.12)	$ (0.09)	$ (0.08)	$ (0.08)	$ (0.06)	$ (0.08)	$ (0.39)	$ (0.31)	$ (0.26)

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Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities - Components of Other Current Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Other Liabilities Disclosure [Abstract]
Deferred revenue, current portion	$ 2,195
Capital lease obligations	2,246	1,471
Other	1,724	399
Total	$ 6,165	$ 1,870

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Business Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2014

Segment Reporting [Abstract]

Summary of Operating Performance of Reportable Segments

The following summarizes the operating performance of our reportable segments (in thousands):

	System One		In-Center		Other			Services			Intersegment Revenue Elimination			Total
Year Ended December 31, 2014
Revenues from external customers	$	212,585	$	78,885	$	8,282		$	1,749		$	—		$	301,501
Intersegment Revenues		846		—		—			—			(846	)		—
Revenues		213,431		78,885		8,282			1,749			(846	)		301,501
Segment profit (loss)		36,802		12,815		(56,878	)		(14,926	)		—			(22,187	)
Depreciation and amortization		20,205		1,608		4,829			1,055			—			27,697
Segment assets		127,212		29,613		136,041			16,860			—			309,726
Year Ended December 31, 2013
Revenues from external customers	$	176,756	$	81,852	$	4,469		$	352		$	—		$	263,429
Intersegment Revenues		—		—		—			—			—			—
Revenues		176,756		81,852		4,469			352			—			263,429
Segment profit (loss)		24,036		16,447		(52,591	)		(5,690	)		—			(17,798	)
Depreciation and amortization		18,041		1,389		5,283			135			—			24,848
Segment assets		110,124		26,414		166,151			4,273			—			306,962
Year Ended December 31, 2012
Revenues from external customers	$	163,129	$	76,927	$	2,076		$	—		$	—		$	242,132
Intersegment Revenues		—		—		—			—			—			—
Revenues		163,129		76,927		2,076			—			—			242,132
Segment profit (loss)		24,349		11,051		(45,388	)		(1,218	)		—			(11,206	)
Depreciation and amortization		18,245		1,461		3,967			—			—			23,673
Segment assets		80,041		20,582		211,326			—			—			311,949

Reconciliation of Total Segment Assets to Total Assets

The following table presents a reconciliation of the total segment assets to total assets (in thousands):

	December 31,
	2014		2013
Total segment assets	$	173,685	$	140,811
Corporate assets:
Cash and cash equivalents		52,884		84,134
Accounts Receivable, net		277		397
Property and equipment, net		17,269		17,000
Intangible assets, net		14,370		17,194
Goodwill		41,817		41,817
Prepaid and other assets		9,424		5,609
Total assets	$	309,726	$	306,962

Total Long-Lived Tangible Assets by Geographic Area

 The following table presents total long-lived tangible assets by geographic area (in thousands):

	December 31,
	2014		2013		2012
United States	$	45,501	$	26,082	$	20,967
Mexico		12,689		10,578		3,949
Other Americas		482		94		—
Total Americas		58,672		36,754		24,916
Germany		21,246		20,235		17,058
Other Europe		7,774		8,530		4,447
Total Europe		29,020		28,765		21,505
Total	$	87,692	$	65,519	$	46,421

Summary of Number of Customers Who Individually Make Up Greater than 10% of Total Revenues

The following table summarizes the number of customers who individually make up greater than ten percent of total revenues:

	Years Ended December 31,
	2014			2013			2012
DaVita		21	%		21	%		21	%
Fresenius		16	%		14	%		11	%
Gambro		9	%		12	%		12	%
Schein		8	%		10	%		11	%

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Business Segment and Geographic Information - Summary of Operating Performance of Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues									$ 301,501	$ 263,429	$ 242,132
Revenues	79,911	75,286	74,083	72,221	69,450	66,873	65,462	61,644	301,501	263,429	242,132
Segment profit (loss)	(4,473)	(6,274)	(6,651)	(4,789)	(4,578)	(4,413)	(4,271)	(4,536)	(22,187)	(17,798)	(11,206)
Depreciation and amortization									27,697	24,848	23,673
Segment assets	309,726				306,962				309,726	306,962	311,949
Operating Segments [Member]
Segment Reporting Information [Line Items]
Segment assets	173,685				140,811				173,685	140,811
Operating Segments [Member] | System One [Member]
Segment Reporting Information [Line Items]
Revenues									212,585	176,756	163,129
Revenues									846
Revenues									213,431	176,756	163,129
Segment profit (loss)									36,802	24,036	24,349
Depreciation and amortization									20,205	18,041	18,245
Segment assets	127,212				110,124				127,212	110,124	80,041
Operating Segments [Member] | In-Center [Member]
Segment Reporting Information [Line Items]
Revenues									78,885	81,852	76,927
Revenues									78,885	81,852	76,927
Segment profit (loss)									12,815	16,447	11,051
Depreciation and amortization									1,608	1,389	1,461
Segment assets	29,613				26,414				29,613	26,414	20,582
Operating Segments [Member] | Services [Member]
Segment Reporting Information [Line Items]
Revenues									1,749	352
Revenues									1,749	352
Segment profit (loss)									(14,926)	(5,690)	(1,218)
Depreciation and amortization									1,055	135
Segment assets	16,860				4,273				16,860	4,273
Other Member]
Segment Reporting Information [Line Items]
Revenues									8,282	4,469	2,076
Revenues									8,282	4,469	2,076
Segment profit (loss)									(56,878)	(52,591)	(45,388)
Depreciation and amortization									4,829	5,283	3,967
Segment assets	136,041				166,151				136,041	166,151	211,326
Intersegment Revenue Elimination [Member]
Segment Reporting Information [Line Items]
Revenues									(846)
Revenues									$ (846)

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Derivative Instruments and Hedging

12 Months Ended

Dec. 31, 2014

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments and Hedging

16. Derivative Instruments and Hedging

We operate a manufacturing and service facility in Mexico and we purchase materials and pay our employees at that facility in pesos, and as such, we are potentially exposed to adverse as well as beneficial movements in foreign currency exchange rates. We enter into foreign exchange forward contracts to minimize the impact of foreign currency exchange rate fluctuations on these peso denominated expenses. These contracts have a duration of up to twelve months and are designated as cash flow hedges. The counterparties to these foreign exchange forward contracts are creditworthy financial institutions; therefore, we do not consider the risk of counterparty nonperformance to be material. The notional amount of our outstanding contracts that are designated as cash flow hedges was $12.5 million and $10.4 million at December 31, 2014 and December 31, 2013, respectively. The fair value of these contracts was recorded on the balance sheet within prepaid expenses and other current assets or other current liabilities depending on the gain (loss) position. The fair value of these contracts was a liability of $1.3 million and $0.2 million at December 31, 2014 and December 31, 2013, respectively.

Gains or losses related to hedge ineffectiveness recognized in earnings were not material during 2014 or 2013. Given the short-term nature of our contracts any gains or losses recorded within accumulated other comprehensive income (loss) will be recognized in earnings within the next twelve months.

The following table presents the effect of these contracts designated as cash flow hedges on our consolidated financial statements (in thousands):

	Gain (Loss) Recognized in OCI (Effective Portion)			Gain (Loss) Reclassified from OCI into Income (Effective Portion)			Classification within the Condensed Consolidated Statement of Comprehensive Loss
Year Ended December 31, 2014	$	(1,223	)	$	(258	)	Cost of revenues
Year Ended December 31, 2013	$	144		$	656		Cost of revenues
Year Ended December 31, 2012	$	498		$	109		Cost of revenues

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Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies Disclosure [Abstract]

Future Minimum Rental Payments under Operating Leases

The future minimum rental payments as of December 31, 2014 under our operating leases are as follows (in thousands):

2015	$	4,412
2016		4,390
2017		4,244
2018		4,369
2019		3,535
Thereafter		8,523
	$	29,473

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Fair Value Measurements

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Measurements

18. Fair Value Measurements

The following tables present assets and liabilities measured at fair value on a recurring basis and their level within the value hierarchy (in thousands):

December 31, 2014	Quoted Prices in Active  Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable  Inputs (Level 3)		Total Fair Value
Assets
Money market funds(1)	$	39,779	$	—	$	—	$	39,779
Liabilities
Foreign exchange forward contracts(2)	$	—	$	1,265	$	—	$	1,265

December 31, 2013	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Fair Value
Assets
Money market funds(1)	$	69,779	$	—	$	—	$	69,779
Foreign exchange forward contracts(2)		—		34		—		34
Liabilities
Foreign exchange forward contracts(2)	$	—	$	192	$	—	$	192
Contingent consideration liability(3)		—		—		540		540

(1) Money market funds are included within cash and cash equivalents.

(2) Foreign exchange forward contracts are included within prepaid expenses and other current assets or other current liabilities depending on the gain (loss) position.

(3) Net present value of expected payments under contingent consideration liability are reported in accrued expenses.

We did not have any transfers between Level 1 and Level 2 during the twelve months ended December 31, 2014 or 2013.

The following table presents the rollforward of the contingent consideration liability classified as Level 3 within the value hierarchy (in thousands):

Balance at December 31, 2013	$	540
Less Payments made		(540	)
Balance at December 31, 2014	$	—

Our contingent consideration liability related to deferred payments made in January and April 2014 in connection with our acquisition of substantially all of the System One assets of Kimal PLC, a distributor of our products in the United Kingdom, on April 2, 2013. The liability recorded at December 31, 2013 was measured using probability weighted discounted cash flow method and includes certain significant unobservable inputs, namely, a discount rate of 11.5% and patient growth rates.

We measure the fair value of our foreign exchange forward contracts classified as derivative instruments using an income approach, based on prevailing market forward rates less the contract rate multiplied by the notional amount. The product of this calculation is then adjusted for counterparty risk.

The carrying amount of our long-term debt approximates fair value at December 31, 2014. The fair value of our long-term debt was estimated using inputs derived principally from market observable data, including current rates offered to us for debt of the same or similar remaining maturities. Within the hierarchy of fair value measurements, these are level 2 inputs.

The carrying amounts reflected in the consolidated balance sheets for cash and cash equivalents, accounts receivable, prepaid expenses and other current and non-current assets, accounts payable and accrued expenses approximate fair value due to their short-term nature.

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Business Segment and Geographic Information - Summary of Number of Customers Who Individually Make Up Greater than 10% of Total Revenues (Detail) (Sales Revenue, Net [Member], Customer Concentration Risk [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
DaVita [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues	21.00%	21.00%	21.00%
Fresenius [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues	16.00%	14.00%	11.00%
Gambro [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues	9.00%	12.00%	12.00%
Schein [Member]
Revenue, Major Customer [Line Items]
Percentage of revenues	8.00%	10.00%	11.00%

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Nature of Operations

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Nature of Operations

1. Nature of Operations

We are a medical device company that develops, manufactures and markets innovative products for the treatment of kidney failure, fluid overload and related blood treatments and procedures. Our primary product, the System One, was designed to satisfy an unmet clinical need for a system that can deliver the therapeutic flexibility and clinical benefits associated with traditional dialysis machines in a smaller, portable, easy-to-use form that can be used by healthcare professionals and trained lay users alike in a variety of settings, including patient homes, as well as more traditional care settings such as hospitals and dialysis centers. Given its design, the System One is particularly well-suited for home hemodialysis and a range of dialysis therapies including more frequent dialysis and nocturnal dialysis, which clinical literature suggests provides patients better clinical outcomes and improved quality of life. The System One is cleared or approved for commercial sale in the U.S., Canada and certain other markets, and is CE marked in the EU, for the treatment of acute and chronic kidney failure and fluid overload. The System One is cleared specifically by the U.S. Food and Drug Administration (FDA) for home hemodialysis and home nocturnal hemodialysis, as well as therapeutic plasma exchange in a clinical environment. The System One is also CE marked in the EU for home nocturnal hemodialysis. In February 2013, we received CE Mark approval and in April 2013 we received clearance from the FDA for the new high flow capabilities with the NxStage System One. We began selling the System One with this feature to both U.S. customers and international distributors in 2014. We also sell, through our Medisystems subsidiary, blood tubing sets and needles primarily to dialysis centers for the treatment of end-stage renal disease (ESRD). These products are cleared or approved for commercial sale in the U.S., Canada and certain other markets and are CE marked in the EU. We believe our largest market opportunity is for the System One used in the home dialysis market for the treatment of ESRD. We operate a small number of NxStage Kidney Care dialysis centers focused on supporting home therapy and providing flexible in-center options with NxStage technology as part of our market development activities to increase home therapy access. We continue to make significant investments in marketing, research and development, and these dialysis centers, all of which are intended to help us to further penetrate and expand the market for our products.

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Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Undesignated preferred stock, par value	$ 0.001	$ 0.001
Undesignated preferred stock, shares authorized	5,000,000	5,000,000
Undesignated preferred stock, shares issued	0	0
Undesignated preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	63,429,005	61,666,048
Treasury stock, shares	772,273	575,895

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Income Taxes

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

The following is a summary of income (loss) before income taxes by geography (in thousands):

	Years Ended December 31,
	2014			2013			2012
U.S.	$	(24,315	)	$	(20,613	)	$	(16,026	)
Foreign		1,255			1,807			1,906
Total	$	(23,060	)	$	(18,806	)	$	(14,120	)

The components of the provision for (benefit from) income taxes are as follows (in thousands):

	Years Ended December 31,
	2014			2013			2012
Current:
U.S. - State	$	57		$	47		$	52
Foreign		1,278			(76	)		1,357
Total Current		1,335			(29	)		1,409
Deferred:
Foreign		(82	)		(216	)		(376	)
Total Deferred		(82	)		(216	)		(376	)
Total Provision (Benefit)	$	1,253		$	(245	)	$	1,033

We recognized a provision for income taxes of $1.3 million during 2014, a benefit from income taxes of $0.2 million during 2013 and a provision for income taxes of $1.0 million during 2012. We recorded income tax expense during 2014, 2013 and 2012 for certain profitable foreign subsidiaries. The net benefit from income taxes recorded during 2013 includes the favorable conclusion of a foreign income tax audit which resulted in the recognition of a $1.2 million income tax benefit and a gain related to a foreign legislative change.

A reconciliation of the U.S. federal statutory tax rate to the effective tax rate is as follows:

	Years Ended December 31,
	2014			2013			2012
Federal statutory rate		34.0	%		34.0	%		34.0	%
Stock compensation		2.0	%		(2.5	)%		(5.6	)%
State income tax, net of federal tax benefit		1.9	%		3.2	%		2.0	%
U.S. research credits		4.1	%		11.7	%		3.3	%
Foreign income inclusion in the U.S.		(2.8	)%		(6.7	)%		(3.1	)%
Valuation allowance		(39.7	)%		(40.2	)%		(31.4	)%
Change in tax reserves		—	%		4.0	%		(5.6	)%
Other, net		(4.9	)%		(2.2	)%		(0.9	)%
Effective tax rate		(5.4	)%		1.3	%		(7.3	)%

The 2013 effective tax rate included a $1.2 million income tax benefit from the favorable conclusion of a foreign income tax audit.

Deferred income tax assets and liabilities reflect the tax effects of differences in the recognition of income and expense items for tax and financial reporting purposes. Deferred tax assets (liabilities), the majority of which are non-current, are made up of the following (in thousands):

	December 31,
	2014			2013
Deferred tax assets:
Net operating loss carryforwards	$	114,131		$	108,772
Tax credits		10,078			9,464
Stock-based compensation		6,259			5,713
Capitalized research and development		3,120			3,677
Financing liabilities		6,281			5,007
Other		6,092			2,199
Total deferred tax assets		145,961			134,832
Deferred tax liabilities:
Fixed assets		(7,719	)		(5,079	)
Intangible assets		(5,326	)		(6,509	)
Other		(608	)		—
Total deferred tax liabilities		(13,653	)		(11,588	)
Net deferred tax assets before valuation allowance		132,308			123,244
Less valuation allowance		(131,453	)		(122,353	)
Net deferred tax assets	$	855		$	891

As of December 31, 2014, we had U.S. federal and state net operating loss carryforwards of approximately $366 million and $187 million, respectively, available to offset future taxable income. A portion of the federal net operating loss, $54.2 million, and state net operating loss, $27.7 million, is attributable to excess tax deductions related to stock-based compensation. We will realize the benefit of these excess tax deductions through increases in shareholder’s equity in future periods when and if the losses are utilized to reduce future tax payments. The federal and state net operating loss carryforwards will expire between 2015 and 2034 if not utilized. Utilization of the net operating loss carryforwards may be subject to annual limitations due to the ownership percentage change limitations provided by the Internal Revenue Code Section 382 and similar state provisions. To date, we have not completed an analysis in accordance with §382. In the event of a deemed change in control under Internal Revenue Code Section 382, an annual limitation imposed on the utilization of net operating losses may result in the expiration of all or a portion of the net operating loss carryforwards. We also had federal and state research and development credit carryforwards of $7.0 million and $1.9 million, respectively, which begin to expire in 2020 if not utilized. We also had foreign tax credits of approximately $1.0 million that will expire between 2018 and 2021 if not utilized. As of December 31, 2014, we have not been subject to a federal income tax audit in the U.S.

During 2014, the deferred tax valuation allowance increased by approximately $9.1 million, primarily as the result of increases to federal, state, and foreign net operating losses. A full valuation allowance has been recorded in the accompanying consolidated financial statements to offset our U.S. and specific foreign deferred tax assets because the future realizability of such assets is uncertain. We believe that the future realization of these assets is not more likely than not given the expected future tax losses in these jurisdictions.

The below table details the changes in unrecognized tax benefits, which if recognized would favorably impact our effective tax rate (in thousands):

	Years Ended December 31,
	2014			2013			2012
Balance at beginning of the year	$	411		$	1,067		$	678
Increase in unrecognized tax benefits current year		88			411			389
Decrease in unrecognized tax benefits prior years		(110	)		—			—
Reductions due to audit settlement		(42	)		(1,067	)		—
Balance at end of year	$	347		$	411		$	1,067

As of December 31, 2014 we had gross unrecognized tax benefits of $0.4 million that, if recognized, would result in a reduction of our effective tax rate. As of December 31, 2013 and 2012 we had gross unrecognized tax benefits of $0.5 million and $1.5 million, respectively, including interest and penalties of $0.1 million and $0.4 million.

We monitor the undistributed earnings of foreign subsidiaries and, as necessary, provide for income taxes on those earnings that are not deemed permanently invested. As of December 31, 2014, there were no significant undistributed earnings of foreign subsidiaries that were deemed permanently invested.

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Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental Disclosures:
Cash paid for interest	$ 671	$ 549	$ 1,457
Cash paid for taxes	903	1,181	586
Noncash Investing and Financing Activities:
Transfers from inventory to field equipment	25,370	13,827	12,172
Transfers from field equipment to deferred cost of revenues	13,110	10,260	10,360
Payment of Corporate Bonus Plan in common stock		1,034	878
Market value of shares received in payment for exercise of stock options	3,026	412	513
Construction-in-process financed by construction liability	4,898	3,568	8,343
Settlement of debt through the issuance of common stock			45,219
Leasehold improvements paid by the landlord	4,300		4,300
Property and equipment acquired under capital lease	76	745	1,615
Acquisition of business		1,757
Increase in deferred revenues related to the new manufacturing facility in Germany	3,608		6,124
Deferred revenues and deferred costs related to acquiree recorded as a reduction of consideration paid		$ 335

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Fair Value Measurements - Roll Forward of Contingent Consideration Liability Classified as Level 3 within Value Hierarchy (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Debt Instrument Fair Value Carrying Value [Abstract]
Balance at December 31, 2013	$ 540
Less: Payments made	(540)
Balance at December 31, 2014	$ 0

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Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Feb. 17, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	NXTM
Entity Registrant Name	NxStage Medical, Inc.
Entity Central Index Key	0001333170
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,707,290
Entity Public Float			$ 870

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Stock Plans and Stock-Based Compensation

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock Plans and Stock-Based Compensation

12. Stock Plans and Stock-Based Compensation

Stock Incentive Plans

We maintain the 2014 Omnibus Incentive Plan (2014 Plan) that governs awards to both employees and non-employees. The 2014 Plan replaced and superseded our 2005 Stock Incentive Plan (2005 Plan) except that awards granted under the 2005 Plan remain in effect pursuant to their original terms. While the 2014 Plan authorizes a variety of equity-based and cash awards, we generally offer equity incentives under the 2014 Plan in the form of restricted stock units, stock options and performance shares. Restricted stock units customarily vest over a period of three or four years. Stock options expire ten years from the date of grant and customarily vest over a period of four years for employees and are fully vested for directors. Performance shares are issued to certain employees and executive officers and entitle recipients to earn restricted stock units based on the achievement of annual corporate financial performance metrics; any earned restricted stock units customarily vest over a period of three years. We settle stock option exercises and the vesting of restricted stock units with newly issued common shares. Pursuant to the 2014 Plan, each share award other than options or stock appreciation rights will reduce the number of total shares available for grant by 1.62 shares. A total of 5.6 million shares, together with any unissued shares that may carry over from the 2005 Plan, have been authorized for grant under the 2014 Plan and at December 31, 2014, 5.3 million shares remained available for future grant.

We offer a corporate bonus plan for the benefit of our employees. Payout under the bonus plan is based on individual performance and the achievement of certain annual corporate financial performance metrics. Bonus awards are paid in cash or, at the discretion of the Compensation Committee of the Board, in shares of our common stock. The estimated payout under our bonus plan is recognized as compensation expense during the performance year and is classified as a liability, until settlement, on our consolidated balance sheet. The compensation expense associated with our bonus plan for the 2014, 2013 and 2012 performance years that has been or is expected to be paid in shares of our common stock has been classified as stock-based compensation expense.

We also maintain the 2005 Employee Stock Purchase Plan (2005 Purchase Plan), which authorizes the issuance of up to 0.7 million shares of common stock to participating employees through a series of periodic offerings. Each six-month offering period begins in January and July. An employee becomes eligible to participate in the 2005 Purchase Plan once he or she has been employed for at least three months and is regularly employed for at least 20 hours per week for more than three months in a calendar year. The price at which employees can purchase common stock in an offering is 95 percent of the closing price of our common stock on the NASDAQ Global Select Market on the lower of the first or last day of the offering period, unless otherwise determined by the Board of Directors or Compensation Committee of the Board. As of December 31, 2014, 0.1 million shares were available for future issuance under the 2005 Purchase Plan.

Stock Options

A summary of the status of stock options granted under all of our plans at December 31, 2014, and changes during the year then ended, is as follows:

Stock Options	Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value		Average Remaining Contractual  Life
						(In thousands)		(In years)
Outstanding at beginning of year		4,825,880		$	10.73
Granted		997,459		$	14.35
Exercised		(1,524,601	)	$	9.04
Forfeited or expired		(196,313	)	$	15.17
Outstanding at end of year		4,102,425		$	12.02	$	24,832		5.18
Fully vested and exercisable		2,822,955		$	11.30	$	19,264		3.73
Fully vested, exercisable and expected to vest		3,956,565		$	11.96	$	24,197		5.06

The aggregate intrinsic value for stock options is calculated based on the market price of our common stock as of December 31, 2014, less the exercise price of the underlying awards, excluding out-of-the-money awards. The total fair value of options that vested during 2014, 2013 and 2012 was $4.9 million, $5.1 million and $5.1 million, respectively. The aggregate intrinsic value of options exercised during 2014, 2013 and 2012 was $9.2 million, $3.5 million and $8.8 million, respectively. The aggregate intrinsic value of options exercised is calculated based on the market price of our common stock on the exercise date, less the exercise price of underlying award.

The weighted-average fair value of options granted during 2014, 2013 and 2012 was $5.80, $6.29 and $9.23 per option, respectively. The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Years Ended December 31,
	2014	2013	2012
Expected life (in years)	4.40 to 5.00	4.50 to 4.70	4.50
Risk-free interest rate	1.56% to 1.69%	0.75% to 1.04%	0.67% to 0.90%
Expected stock price volatility	43% to 45%	62%	70%
Expected dividend yield	—	—	—

Restricted Stock

The total fair value of restricted stock that vested was $3.2 million, $2.8 million and $3.7 million during 2014, 2013 and 2012, respectively. The weighted-average fair value of restricted stock granted during 2014, 2013 and 2012 was $14.35, $11.97 and $16.89 per unit, respectively. The following table summarizes the status of the unvested restricted stock:

	Shares			Weighted  Average Grant-date Fair Value		Aggregate Intrinsic  Value		Weighted  Average Remaining Contractual Life
						(In thousands)		(In years)
Unvested at December 31, 2013		734,221		$	14.72
Granted		699,913		$	14.35
Vested		(192,741	)	$	16.64
Forfeited		(51,548	)	$	13.94
Unvested at December 31, 2014		1,189,845		$	14.23	$	21,334		1.89

The aggregate intrinsic value for restricted stock is calculated based on the market price of our common stock as of December 31, 2014.

Employee Stock Purchase Plan

The weighted-average fair value of stock purchase rights granted as part of the 2005 Purchase Plan during 2014, 2013 and 2012 was $1.46, $3.10 and $4.57 per share, respectively. The fair value of the employees’ stock purchase rights was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Years Ended December 31,
	2014	2013	2012
Expected life (in months)	6	6	6
Risk-free interest rate	0.07% to 0.10%	0.09% to 0.12%	0.06% to 0.15%
Expected stock price volatility	26.3% to 27.4%	20.1% to 33.6%	23.3% to 36.0%
Expected dividend yield	—	—	—

There were 70,899, 75,301 and 56,691 shares issued under the 2005 Purchase Plan during 2014, 2013 and 2012, respectively, which resulted in share-based compensation expense of $0.1 million, $0.1 million, and $0.2 million in 2014, 2013 and 2012, respectively.

Stock-based Compensation Expense

The following table presents stock-based compensation expense included in the consolidated statements of comprehensive loss (in thousands):

	Years Ended December 31,
	2014		2013		2012
Cost of revenues	$	1,212	$	918	$	1,168
Selling and marketing		4,442		3,171		4,186
Research and development		1,726		1,331		1,372
General and administrative		5,501		3,218		4,677
Total stock-based compensation expense	$	12,881	$	8,638	$	11,403

As of December 31, 2014, approximately $19 million of unrecognized stock compensation cost related to nonvested stock options and restricted stock (net of estimated forfeitures) is expected to be recognized over a weighted-average period of 2.6 years.

Other Compensation Plans

We maintain postemployment benefit plans for employees in certain foreign subsidiaries. These unfunded plans provide lump sum benefits, payable based on statutory regulations for voluntary or involuntary termination. We have recorded a liability of $1.7 million and $1.8 million at December 31, 2014 and 2013, respectively, as other long-term liabilities for costs associated with these plans. The expense recorded in connection with these plans was not significant during 2014, 2013 and 2012.

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Stock Plans and Stock-Based Compensation - Summary of Status of Unvested Restricted Stock Units (Detail) (Restricted Stock [Member], USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested at December 31, 2013	734,221
Shares, granted	699,913
Shares, vested	(192,741)
Shares, Forfeited	(51,548)
Unvested at December 31, 2014	1,189,845	734,221
Weighted average grant date fair value unvested, Beginning balance	$ 14.72
Weighted average grant date fair value, granted	$ 14.35	$ 11.97	$ 16.89
Weighted average grant date fair value, vested	$ 16.64
Weighted average grant-date fair value, forfeited	$ 13.94
Weighted average grant date fair value unvested, Ending balance	$ 14.23	$ 14.72
Aggregate intrinsic value unvested, Beginning balance
Aggregate intrinsic value unvested, Ending balance	$ 21,334
Weighted average remaining contractual life unvested, Ending balance	1 year 10 months 21 days

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Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Fair Value Measurements, Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Liabilities
Contingent consideration liability		$ 540
Foreign Exchange Forward Contracts [Member]
Assets
Foreign exchange forward contracts		34
Liabilities
Foreign exchange forward contracts	1,265	192
Significant Other Observable Inputs (Level 2) [Member] | Foreign Exchange Forward Contracts [Member]
Assets
Foreign exchange forward contracts		34
Liabilities
Foreign exchange forward contracts	1,265	192
Significant Unobservable Inputs (Level 3) [Member]
Liabilities
Contingent consideration liability		540
Money Market Funds [Member]
Assets
Money market funds	39,779	69,779
Money Market Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets
Money market funds	$ 39,779	$ 69,779

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Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Revenues	$ 301,501	$ 263,429	$ 242,132
Cost of revenues	185,598	160,926	149,324
Gross profit	115,903	102,503	92,808
Operating expenses:
Selling and marketing	55,385	47,842	40,485
Research and development	22,635	18,887	17,111
Distribution	26,001	21,246	18,888
General and administrative	34,069	32,326	27,530
Total operating expenses	138,090	120,301	104,014
Loss from operations	(22,187)	(17,798)	(11,206)
Other expense:
Interest expense	(863)	(611)	(2,766)
Other expense, net	(10)	(397)	(148)
Total other expenses	(873)	(1,008)	(2,914)
Net loss before income taxes	(23,060)	(18,806)	(14,120)
Provision for (benefit from) income taxes	1,253	(245)	1,033
Net loss	(24,313)	(18,561)	(15,153)
Less: Net loss attributable to noncontrolling interests	(367)
Net loss attributable to stockholders of NxStage Medical, Inc.	(23,946)	(18,561)	(15,153)
Net loss per share, basic and diluted	$ (0.39)	$ (0.31)	$ (0.26)
Weighted-average shares outstanding, basic and diluted	61,700	60,261	57,890
Other comprehensive (loss) income, net of tax	(2,404)	(258)	538
Total comprehensive loss	(26,717)	(18,819)	(14,615)
Less: Comprehensive loss attributable to noncontrolling interests	(367)
Total comprehensive loss attributable to stockholders of NxStage Medical, Inc.	$ (26,350)	$ (18,819)	$ (14,615)

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Net Loss per Share

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Net Loss per Share

6. Net Loss per Share

Basic net loss per share is computed by dividing loss available to NxStage Medical, Inc. common stockholders (the numerator) by the weighted-average number of common shares outstanding (the denominator) for the period. The computation of diluted loss per share is similar to basic loss per share, except that the denominator is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued.

The following potential common stock equivalents, as calculated using the treasury stock method, were not included in the computation of diluted net loss per share as their effect would have been anti-dilutive due to the net loss incurred (in thousands):

	Years Ended December 31,
	2014		2013		2012
Options to purchase common stock		876		1,013		1,602
Unvested restricted stock		236		152		196
Warrants to purchase common stock		—		—		921
Total		1,112		1,165		2,719

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Intangible Assets

12 Months Ended

Dec. 31, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

5. Intangible Assets

The components of intangible assets, net are as follows (in thousands):

	December 31, 2014					December 31, 2013					Estimated Useful Life
	Cost		Accumulated Amortization			Cost		Accumulated Amortization
Bloodline, needle and other patented and unpatented technology	$	6,200	$	(5,619	)	$	6,200	$	(4,844	)		8 years
Trade names		2,300		(1,191	)		2,300		(1,026	)		14 years
Customer relationships		26,175		(13,495	)		26,185		(11,621	)		10/14 years
Intangible assets, net	$	34,675	$	(20,305	)	$	34,685	$	(17,491	)

We recognized amortization expense of $2.8 million during each of 2014, 2013 and 2012.

The estimated future aggregated amortization expense for intangible assets as of December 31, 2014 is as follows (in thousands):

2015	$	2,621
2016		2,040
2017		2,040
2018		2,040
2019		2,040
Thereafter		3,589
	$	14,370

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Accumulated Other Comprehensive (Loss) Income

12 Months Ended

Dec. 31, 2014

Equity [Abstract]

Accumulated Other Comprehensive (Loss) Income

17. Accumulated Other Comprehensive (Loss) Income

The following additional information is provided with respect to the accumulated other comprehensive (loss) income as presented on the condensed consolidated balance sheets (in thousands):

	Unrealized gain (loss) on derivative instruments			Other (2)			Total
Balance, net of tax, as of December 31, 2011	$	—		$	(68	)	$	(68	)
Other comprehensive income before reclassifications		498			149			647
Gain reclassified to earnings (1)		(109	)		—			(109	)
Total other comprehensive income		389			149			538
Balance, net of tax, as of December 31, 2012	$	389		$	81		$	470
Other comprehensive income before reclassifications		144			254			398
Gain reclassified to earnings (1)		(656	)		—			(656	)
Total other comprehensive income (loss)		(512	)		254			(258	)
Balance, net of tax, as of December 31, 2013	$	(123	)	$	335		$	212
Other comprehensive loss before reclassifications		(1,223	)		(1,439	)		(2,662	)
Loss reclassified to earnings (1)		258			—			258
Total other comprehensive loss		(965	)		(1,439	)		(2,404	)
Balance, net of tax, as of December 31, 2014	$	(1,088	)	$	(1,104	)	$	(2,192	)

(1) Reclassifications of gains (losses) on derivative instruments are included in cost of revenues on the consolidated statement of comprehensive loss. See Note 16 for further information.

(2) Other includes cumulative translation adjustments and, to a lesser extent, pension benefits.

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Employee Benefit Plan

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

Employee Benefit Plan

13. Employee Benefit Plan

We have a 401(k) retirement plan (401(k) Plan) for the benefit of eligible employees, as defined. Each participant may elect to contribute up to 75% of his or her compensation to the 401(k) Plan each year, subject to certain IRS limitations. We contribute 100% of the first 3% of the employee’s contribution and 50% of the next 2% of the employee’s contribution. We contributed $1.7 million, $1.5 million and $1.3 million to the 401(k) Plan during 2014, 2013 and 2012, respectively.

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Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Repayment of principal amount and interest			$ 45.2
Issuance of common stock for debt repayment			2,456,246
Number of shares retained for payment of minimum withholding taxes			28,351
Issuance of common stock for debt repayment, net			2,427,895
Warrants issued to purchase common stock		1,900,000
Exercise price of warrants, per share		$ 5.50
Shares delivered or surrendered in payment for the exercise of stock options	196,378	34,311	32,310

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Business Segment and Geographic Information

12 Months Ended

Dec. 31, 2014

Segment Reporting [Abstract]

Business Segment and Geographic Information

9. Business Segment and Geographic Information

With our continued investment in our NxStage Kidney Care dialysis centers, effective with the first quarter of 2014, it was determined that the operations of NxStage Kidney Care should be presented separately. Prior to 2014, its operations were included within the Other category. We now have three reportable business segments: System One, In-Center, and Services. The operating results of NxStage Kidney Care are included in our Services segment. We distribute our products in three markets: home, critical care and in-center. Prior period information has been updated to conform with the current presentation.

Our System One segment includes revenues from the sale and rental of the System One and PureFlow SL dialysate preparation equipment and the sale of disposable products in the home and critical care markets. The home market is devoted to the treatment of ESRD patients in the home or a home-like setting, while the critical care market is devoted to the treatment of hospital-based patients with acute kidney failure or fluid overload. Some of our largest customers in the home market provide outsourced renal dialysis services to some of our customers in the critical care market. Sales of product to both markets are made primarily through dedicated sales forces and distributed directly to the customer, or the patient, with certain products sold through distributors. The results of our international business are included in the System One segment.

Our In-Center segment includes revenues from the sale of blood tubing sets and needles for hemodialysis primarily for the treatment of ESRD patients at dialysis centers and needles for apheresis. Nearly all In-Center products are sold through national distributors.

Our Services segment includes revenues from dialysis services provided to patients at our NxStage Kidney Care dialysis centers.

The remainder of our operations and financial information, included within the Other category, relates primarily to the manufacturing of dialyzers for sale to Asahi and research and development and general and administrative expenses that are excluded from the segment operating performance measures.

The accounting policies of our reportable segments are the same as those described in Note 2. Our chief operating decision maker allocates resources to our business segments and assesses segment performance based on segment profit (loss), which consists of revenues less cost of revenues, selling and marketing and distribution expenses.

The following summarizes the operating performance of our reportable segments (in thousands):

	System One		In-Center		Other			Services			Intersegment Revenue Elimination			Total
Year Ended December 31, 2014
Revenues from external customers	$	212,585	$	78,885	$	8,282		$	1,749		$	—		$	301,501
Intersegment Revenues		846		—		—			—			(846	)		—
Revenues		213,431		78,885		8,282			1,749			(846	)		301,501
Segment profit (loss)		36,802		12,815		(56,878	)		(14,926	)		—			(22,187	)
Depreciation and amortization		20,205		1,608		4,829			1,055			—			27,697
Segment assets		127,212		29,613		136,041			16,860			—			309,726
Year Ended December 31, 2013
Revenues from external customers	$	176,756	$	81,852	$	4,469		$	352		$	—		$	263,429
Intersegment Revenues		—		—		—			—			—			—
Revenues		176,756		81,852		4,469			352			—			263,429
Segment profit (loss)		24,036		16,447		(52,591	)		(5,690	)		—			(17,798	)
Depreciation and amortization		18,041		1,389		5,283			135			—			24,848
Segment assets		110,124		26,414		166,151			4,273			—			306,962
Year Ended December 31, 2012
Revenues from external customers	$	163,129	$	76,927	$	2,076		$	—		$	—		$	242,132
Intersegment Revenues		—		—		—			—			—			—
Revenues		163,129		76,927		2,076			—			—			242,132
Segment profit (loss)		24,349		11,051		(45,388	)		(1,218	)		—			(11,206	)
Depreciation and amortization		18,245		1,461		3,967			—			—			23,673
Segment assets		80,041		20,582		211,326			—			—			311,949

The following table presents a reconciliation of the total segment assets to total assets (in thousands):

	December 31,
	2014		2013
Total segment assets	$	173,685	$	140,811
Corporate assets:
Cash and cash equivalents		52,884		84,134
Accounts Receivable, net		277		397
Property and equipment, net		17,269		17,000
Intangible assets, net		14,370		17,194
Goodwill		41,817		41,817
Prepaid and other assets		9,424		5,609
Total assets	$	309,726	$	306,962

Long-lived tangible assets consist of property and equipment, net and field equipment, net. The following table presents total long-lived tangible assets by geographic area (in thousands):

	December 31,
	2014		2013		2012
United States	$	45,501	$	26,082	$	20,967
Mexico		12,689		10,578		3,949
Other Americas		482		94		—
Total Americas		58,672		36,754		24,916
Germany		21,246		20,235		17,058
Other Europe		7,774		8,530		4,447
Total Europe		29,020		28,765		21,505
Total	$	87,692	$	65,519	$	46,421

Substantially all of our revenues are derived from the sale of the System One and related products, which cannot be used with any other dialysis system, and from needles and blood tubing sets to customers located in the U.S.

The following table summarizes the number of customers who individually make up greater than ten percent of total revenues:

	Years Ended December 31,
	2014			2013			2012
DaVita		21	%		21	%		21	%
Fresenius		16	%		14	%		11	%
Gambro		9	%		12	%		12	%
Schein		8	%		10	%		11	%

Sales to DaVita HealthCare Partners Inc. (DaVita) and Fresenius Medical Care (Fresenius) are in the System One segment. Sales to Gambro AB and Henry Schein, Inc. (Schein) are in the In-Center segment. All of Gambro’s sales of our products are to DaVita. A portion of Schein’s sales of our products are to DaVita.

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Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities - Components of Other Long-term Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Other Liabilities, Noncurrent [Abstract]
Capital lease obligations	$ 11,876	$ 14,133
Lease incentive obligations	4,569	3,589
Benefit plan obligations	1,745	1,770
Other	1,434	781
Total	$ 19,624	$ 20,273

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Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities

12 Months Ended

Dec. 31, 2014

Payables and Accruals [Abstract]

Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities

7. Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities

The components of accrued expenses are as follows (in thousands):

	December 31,
	2014		2013
Payroll, compensation and related benefits	$	12,346	$	9,041
Distribution expenses		3,069		2,762
General and administrative expenses		3,075		2,207
Audit, legal, and consulting fees		1,394		2,725
Other		4,769		4,290
Total	$	24,653	$	21,025

The components of other current liabilities are as follows (in thousands):

	December 31,
	2014		2013
Deferred revenue, current portion	$	2,195	$	—
Capital lease obligations		2,246		1,471
Other		1,724		399
Total	$	6,165	$	1,870

The components of other long term liabilities are as follows (in thousands):

	December 31,
	2014		2013
Capital lease obligations	$	11,876	$	14,133
Lease incentive obligations		4,569		3,589
Benefit plan obligations		1,745		1,770
Other		1,434		781
Total	$	19,624	$	20,273

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Debt and Capital Lease Obligations

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Debt and Capital Lease Obligations

8. Debt and Capital Lease Obligations

Manufacturing Facility in Italy

We entered into two euro denominated mortgages collateralized by a manufacturing facility in Italy that we acquired in May 2013. The first mortgage is in the principal amount of $0.6 million, subject to an annual interest rate of 6.0%, and payable quarterly over a 10 year period. The second mortgage is in the principal amount of $0.5 million, subject to an annual interest rate of 2.0%, and payable biannually over a 10 year period.

Loan and Security Agreements

We had a loan and security agreement with Silicon Valley Bank, or SVB, that provided for a $15.0 million revolving line of credit. This agreement matured as of March 31, 2014.

On June 10, 2014, we entered into a new revolving line of credit with General Electric Capital Corporation, or GECC, and SVB that allows for borrowings up to $35 million. Availability of credit is subject to a borrowing base that is calculated with reference to certain of our accounts receivable, inventory and equipment, and adjustments to such borrowing base are at the discretion of the lenders. The new revolving line of credit is secured by substantially all of our assets and expires in June 2019. Borrowings bear interest at an annual rate equal to (1) a LIBOR rate plus 2.5% or (2) a base rate plus 1.5%, where the base rate is the highest of (a) the Prime Rate, (b) the Federal Funds Rate plus 0.5% and (c) a LIBOR rate plus 1%, at our election. The new revolving credit facility requires us to comply with certain covenants while borrowings are outstanding and contains events of default customary for a transaction of this type.

As of December 31, 2014, there were no outstanding borrowings under the $35 million revolving line of credit, we were in compliance with all applicable covenants and, subject to the lenders’ adjustments described above, we had approximately $28 million of credit commitment available for borrowing.

Capital Lease Obligations

Our capital lease obligations consist of certain property and equipment financed through capital leases and our capital lease obligation due to Asahi related to the manufacturing facility in Germany. Approximate future minimum payments under our capital leases as of December 31, 2014 are as follows (in thousands):

2015	$	2,326
2016		2,312
2017		1,925
2018		1,506
2019		851
Thereafter (1)		9,065
Total minimum lease payments		17,985
Less amount representing interest		(3,863	)
Present value of future minimum lease payments	$	14,122

(1) Amount includes $6.6 million representing the estimated residual value of the manufacturing facility in Germany at the end of the estimated lease term, which only becomes due and payable at Asahi’s option if we terminate our agreement with Asahi.

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Commitments and Contingencies

12 Months Ended

Dec. 31, 2014

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. Commitments and Contingencies

Purchase Commitments

We have agreements with certain of our suppliers, primarily for the purchase of certain System One components and fluids along with needles for our In-Center segment that include minimum purchase commitments. As of December 31, 2014, we had a total of $62.3 million in minimum purchase commitments under these agreements over the next one to five years.

Operating Leases

Our operating leases relate to our corporate headquarters and NxStage Kidney Care facilities, as well as our foreign leased manufacturing facilities in Mexico, Germany and Italy.

Our corporate headquarters lease has an initial term of eleven years through mid-2023 with an early termination provision after seven years, subject to certain terms and conditions, with two 5-year options to extend beyond the initial term on substantially the same terms and at rent equal to ninety-five percent of the then fair market value. The lease included a tenant improvement allowance of $4.3 million.

Our NxStage Kidney Care facility lease agreements have initial lease terms through 2018 to 2022, contain renewal options ranging from five to ten years at the fair rental value at the time of renewal. The leases are generally subject to periodic consumer price index increases or contain fixed escalation clauses and include tenant improvement allowances ranging from $0.1million to $0.3 million per facility.

Our foreign leased manufacturing facilities are subject to lease agreements with termination dates through December 2015 to 2018 and contain renewal options at the fair rental value at the time of renewal.

Our lease agreements contain certain provisions that require us to pay executory costs such as real estate taxes, operating expenses and common utilities. Rent expense is recorded on a straight-line basis over the lease term. Tenant improvement allowances are recorded as a deferred rent obligation and amortized to rent expense over the term of the lease.

Rent expense under our operating leases was $3.8 million during 2014, $2.2 million during 2013 and $2.2 million during 2012.

The future minimum rental payments as of December 31, 2014 under our operating leases are as follows (in thousands):

2015	$	4,412
2016		4,390
2017		4,244
2018		4,369
2019		3,535
Thereafter		8,523
	$	29,473

Contingencies

A civil complaint was filed against us on February 28, 2012 by Gambro Renal Products, Inc., or Gambro. The complaint alleged that we made false and misleading statements about our and Gambro’s allegedly competing products in the critical care market in commercial and promotional activities. The complaint also alleged that we wrongfully interfered with contractual and advantageous relationships of Gambro in its critical care business.

Effective January 2, 2014, we and Gambro agreed to a settlement of this litigation without any admission of wrongdoing or liability. The settlement required us to pay a one-time cash payment to Gambro which was primarily offset by reimbursement from our insurance company. At the same time, we entered into a patent cross-license agreement and a distribution agreement amendment that amended the length and other terms of the agreement between us and Gambro. We recorded the settlement, reimbursement and consideration within general and administrative expense on the consolidated statements of comprehensive loss.

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Business Segment and Geographic Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014 Markets Segment
Segment Reporting [Abstract]
Number of reporting segments	3
Number of markets product distributed	3

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Business Combination - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Business acquisition, cash paid		$ 2,234,000
Discount rate used in determining fair value of customer relationships	11.50%
Customer Relationships [Member]
Business Acquisition [Line Items]
Discount rate used in determining fair value of customer relationships	11.50%
Kimal PLC [Member]
Business Acquisition [Line Items]
Business acquisition, aggregate purchase price		4,000,000
Business acquisition, cash paid	100,000	2,200,000
Business acquisition, liabilities assumed		1,500,000
Business acquisition, contingent consideration		500,000
Business acquisition,reclassification of deferred revenues		$ 300,000

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Business Segment and Geographic Information - Reconciliation of Total Segment Assets to Total Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 309,726	$ 306,962	$ 311,949
Cash and cash equivalents	52,884	84,134	106,439	102,909
Property and equipment, net	66,574	52,478
Intangible assets, net	14,370	17,194
Goodwill	41,817	41,817
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	173,685	140,811
Other Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	136,041	166,151	211,326
Cash and cash equivalents	52,884	84,134
Accounts Receivable, net	277	397
Property and equipment, net	17,269	17,000
Intangible assets, net	14,370	17,194
Goodwill	41,817	41,817
Prepaid and other assets	$ 9,424	$ 5,609

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Debt and Capital Lease Obligations - Schedule of Future Minimum Payments Under Capital Leases (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Debt Disclosure [Abstract]
Estimated residual value of manufacturing facility	$ 6.6

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Fair Value Measurements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Discount rate	11.50%

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Debt and Capital Lease Obligations (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Schedule of Future Minimum Payments under Capital Leases

Approximate future minimum payments under our capital leases as of December 31, 2014 are as follows (in thousands):

2015	$	2,326
2016		2,312
2017		1,925
2018		1,506
2019		851
Thereafter (1)		9,065
Total minimum lease payments		17,985
Less amount representing interest		(3,863	)
Present value of future minimum lease payments	$	14,122

(1) Amount includes $6.6 million representing the estimated residual value of the manufacturing facility in Germany at the end of the estimated lease term, which only becomes due and payable at Asahi’s option if we terminate our agreement with Asahi.

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Property and Equipment, Field Equipment and Deferred Cost of Revenues - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Depreciation expense for property and equipment	$ 7,100,000	$ 4,700,000	$ 3,700,000
Capitalized computer development costs	3,600,000
Amortization of capitalized computer development costs	900,000
Asset placed in service	66,574,000	52,478,000
Fair value in relation with incremental borrowing rate	50.00%
Amortization expense of deferred cost of revenue	13,500,000	13,300,000	13,500,000
Germany [Member]
Property, Plant and Equipment [Line Items]
Percentage of payments capped as cost of facility	50.00%
Percentage of purchase price to net book value of facility	100.00%
Capital lease obligation	12,700,000
Deferred revenues	8,200,000
Manufacturing Facility [Member]
Property, Plant and Equipment [Line Items]
Asset placed in service	6,400,000
Manufacturing Facility [Member] | Germany [Member]
Property, Plant and Equipment [Line Items]
Capital lease obligation	3,500,000
Deferred revenues	2,900,000
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Construction-in-process of capitalized computer development costs	0	4,500,000
Field Equipment [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense for field equipment	$ 4,200,000	$ 4,000,000	$ 3,700,000

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Business Combination

12 Months Ended

Dec. 31, 2014

Business Combinations [Abstract]

Business Combination

15. Business Combination

During 2013, we acquired substantially all of the System One assets of Kimal PLC, or Kimal, a distributor of our products in the United Kingdom. The acquisition was consistent with our move to a direct sales model in the United Kingdom. The aggregate purchase price of $4.0 million include cash payments of $0.1 million and $2.2 million paid in 2014 and 2013, respectively, the forgiveness of a capital lease liability due from Kimal of $1.5 million, contingent consideration of $0.5 million paid in 2014 and offset by the reclassification of deferred revenues of $0.3 million, net of related deferred cost of revenues, associated with sales of equipment to Kimal prior to January 1, 2011.

The following table presents the allocation of the purchase price to the estimated fair value of the assets acquired (in thousands):

Assets purchased:
Inventory	$	523
Field Equipment		3,298
Customer relationships		170
Assets acquired	$	3,991

The fair values of inventory and field equipment noted above approximated their net book value at the time of acquisition. The customer relationships were valued using the multi-period excess-earnings method, a form of the income approach, using certain significant unobservable inputs (classified as level 3 in the fair value hierarchy), namely, a discount rate of 11.5%, projected future cash flows, and patient growth rates.

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Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

20. Quarterly Financial Data (Unaudited)

The following table sets forth selected quarterly information (unaudited) (in thousands, except per share data):

	Three Months Ended
	March 31, 2014			June 30, 2014			September 30, 2014			December 31, 2014
Revenues	$	72,221		$	74,083		$	75,286		$	79,911
Gross profit		28,934			27,530			28,587			30,852
Loss from operations		(4,789	)		(6,651	)		(6,274	)		(4,473	)
Net loss attributable to stockholders of NxStage Medical, Inc.		(5,275	)		(7,113	)		(6,706	)		(4,852	)
Net loss per share, basic and diluted	$	(0.09	)	$	(0.12	)	$	(0.11	)	$	(0.08	)

	Three Months Ended
	March 31, 2013			June 30, 2013			September 30, 2013			December 31, 2013
Revenues	$	61,644		$	65,462		$	66,873		$	69,450
Gross profit		24,000			25,087			25,528			27,888
Loss from operations		(4,536	)		(4,271	)		(4,413	)		(4,578	)
Net loss attributable to stockholders of NxStage Medical, Inc.		(4,994	)		(3,405	)		(4,986	)		(5,176	)
Net loss per share, basic and diluted	$	(0.08	)	$	(0.06	)	$	(0.08	)	$	(0.08	)

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Inventory - Components of Inventory (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
Purchased components	$ 19,238	$ 15,946
Work in process	9,981	10,762
Finished goods	16,182	11,093
Total	$ 45,401	$ 37,801

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Accumulated Other Comprehensive (Loss) Income (Tables)

12 Months Ended

Dec. 31, 2014

Equity [Abstract]

Summary of Additional Information on Accumulated Other Comprehensive (Loss) Income

The following additional information is provided with respect to the accumulated other comprehensive (loss) income as presented on the condensed consolidated balance sheets (in thousands):

	Unrealized gain (loss) on derivative instruments			Other (2)			Total
Balance, net of tax, as of December 31, 2011	$	—		$	(68	)	$	(68	)
Other comprehensive income before reclassifications		498			149			647
Gain reclassified to earnings (1)		(109	)		—			(109	)
Total other comprehensive income		389			149			538
Balance, net of tax, as of December 31, 2012	$	389		$	81		$	470
Other comprehensive income before reclassifications		144			254			398
Gain reclassified to earnings (1)		(656	)		—			(656	)
Total other comprehensive income (loss)		(512	)		254			(258	)
Balance, net of tax, as of December 31, 2013	$	(123	)	$	335		$	212
Other comprehensive loss before reclassifications		(1,223	)		(1,439	)		(2,662	)
Loss reclassified to earnings (1)		258			—			258
Total other comprehensive loss		(965	)		(1,439	)		(2,404	)
Balance, net of tax, as of December 31, 2014	$	(1,088	)	$	(1,104	)	$	(2,192	)

(1) Reclassifications of gains (losses) on derivative instruments are included in cost of revenues on the consolidated statement of comprehensive loss. See Note 16 for further information.

(2) Other includes cumulative translation adjustments and, to a lesser extent, pension benefits.

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Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Parent [Member]	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2011	$ 151,186	$ 56	$ 489,542	$ (329,828)	$ (68)	$ (8,516)	$ 151,186
Beginning balance, Shares at Dec. 31, 2011		56,167,090
Net loss	(15,153)			(15,153)			(15,153)
Adjustments to other comprehensive loss, net of tax	538				538		538
Issuance of common stock, net of issuance costs	44,554	2	45,074			(522)	44,554
Issuance of common stock, net of issuance costs, Shares		2,456,246
Exercise of stock options	5,832	1	6,344			(513)	5,832
Exercise of stock options, Shares		913,066
Shares issued under employee restricted stock plans	(1,173)		(1,173)				(1,173)
Shares issued under employee restricted stock plans, Shares		200,587
Shares issued under employee bonus plans	878		878				878
Shares issued under employee bonus plans, Shares		47,533
Shares issued under employee stock purchase plan	731		731				731
Shares issued under employee stock purchase plan, Shares		56,691
Shares issued to Directors in lieu of cash	138		138				138
Shares issued to Directors in lieu of cash, Shares		8,904
Stock-based compensation expense	10,060		10,060				10,060
Ending balance at Dec. 31, 2012	197,591	59	551,594	(344,981)	470	(9,551)	197,591
Ending balance, Shares at Dec. 31, 2012		59,850,117
Net loss	(18,561)			(18,561)			(18,561)
Adjustments to other comprehensive loss, net of tax	(258)				(258)		(258)
Exercise of stock options	4,255	1	4,666			(412)	4,255
Exercise of stock options, Shares		662,767
Exercise of warrants	893	1	892				893
Exercise of warrants, Shares		874,921
Shares issued under employee restricted stock plans	(424)		(424)				(424)
Shares issued under employee restricted stock plans, Shares		105,573
Shares issued under employee bonus plans	1,034		1,034				1,034
Shares issued under employee bonus plans, Shares		93,778
Shares issued under employee stock purchase plan	759		759				759
Shares issued under employee stock purchase plan, Shares		75,301
Shares issued to Directors in lieu of cash	42		42				42
Shares issued to Directors in lieu of cash, Shares		3,591
Stock-based compensation expense	8,905		8,905				8,905
Contributions from noncontrolling interest	525							525
Ending balance at Dec. 31, 2013	194,761	61	567,468	(363,542)	212	(9,963)	194,236	525
Ending balance, Shares at Dec. 31, 2013		61,666,048
Net loss	(24,313)			(23,946)			(23,946)	(367)
Adjustments to other comprehensive loss, net of tax	(2,404)				(2,404)		(2,404)
Exercise of stock options	10,751	2	13,775			(3,026)	10,751
Exercise of stock options, Shares	1,524,601	1,524,601
Shares issued under employee restricted stock plans	(422)		(422)				(422)
Shares issued under employee restricted stock plans, Shares		166,127
Shares issued under employee stock purchase plan	804		804				804
Shares issued under employee stock purchase plan, Shares		70,899
Shares issued to Directors in lieu of cash	18		18				18
Shares issued to Directors in lieu of cash, Shares		1,330
Stock-based compensation expense	11,430		11,430				11,430
Contributions from noncontrolling interest	930							930
Ending balance at Dec. 31, 2014	$ 191,555	$ 63	$ 593,073	$ (387,488)	$ (2,192)	$ (12,989)	$ 190,467	$ 1,088
Ending balance, Shares at Dec. 31, 2014		63,429,005

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Derivative Instruments and Hedging - Effect of Contracts Designated as Cash Flow Hedges on Consolidated Financial Statements (Detail) (Cost of Revenues [Member], Cash Flow Hedges [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cost of Revenues [Member] | Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ (1,223)	$ 144	$ 498
Gain (Loss) Reclassified from OCI into Income (Effective Portion)	$ (258)	$ 656	$ 109
Classification within the Condensed Consolidated Statement of Comprehensive Loss	Cost of revenues

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Property and Equipment, Field Equipment and Deferred Cost of Revenues

12 Months Ended

Dec. 31, 2014

Property, Plant and Equipment [Abstract]

Property and Equipment, Field Equipment and Deferred Cost of Revenues

4. Property and Equipment, Field Equipment and Deferred Cost of Revenues

Property and Equipment, net

The components of property and equipment, net are as follows (in thousands):

	December 31,
	2014			2013
Manufacturing equipment and tooling	$	34,621		$	24,963
Leasehold improvements		18,485			11,883
Computer and office equipment		8,935			4,132
Molds		5,377			3,817
Furniture		2,410			1,712
Buildings		8,907			10,005
Land		1,110			1,258
Construction-in-process		14,609			16,500
		94,454			74,270
Less accumulated depreciation		(27,880	)		(21,792	)
Property and equipment, net	$	66,574		$	52,478

Depreciation expense, including amortization of capital leases, for property and equipment was $7.1 million, $4.7 million and $3.7 million during 2014, 2013 and 2012, respectively.

Included in construction-in-process as of December 31, 2013 was $4.5 million of capitalized computer development costs. There were no such costs included in construction-in-process at December 31, 2014. Capitalized computer development costs, net was $3.6 million at December 31, 2014 and we recognized amortization expense of $0.9 million during 2014.

Our property and equipment includes the following amounts for assets subject to capital leases (amounts in thousands):

	December 31, 2014
Manufacturing facility in Germany	$	22,750
Other assets subject to capital leases		2,438
Less accumulated depreciation		(2,905	)
Assets subject to capital leases, net	$	22,283

Manufacturing Facility in Germany

Pursuant to our Dialyzer Production Agreement entered into in May 2009 with Asahi we agreed to oversee construction of a new manufacturing facility in Germany. Asahi funded construction costs of the facility, including land, building and equipment; however, given our involvement during construction we were considered the owner of the facility for accounting purposes and therefore, as required, we recorded the cost of the new facility within property and equipment on our consolidated balance sheet along with a corresponding liability within other long-term liabilities for the construction cost funded by Asahi.

Pursuant to the Dialyzer Production Agreement, we agreed to operate the facility and manufacture dialyzers for our own use and for sale to Asahi under a manufacturing agreement during the initial term of the agreement through June 2021 and thereafter, unless either party provides notice of its intent not to renew. Asahi agreed to pay us cost including material, labor and overhead (but excluding depreciation on the new facility), plus applicable statutory value added or turnover tax established or required by law for each dialyzer manufactured by us for Asahi. We are required to pay Asahi a fixed amount per dialyzer manufactured for our own use in the facility, with such payments capped at fifty percent of the cost of the facility paid by Asahi. If the agreement is terminated subsequent to completion of construction by us, Asahi has the option to require us to purchase the facility from them or if the agreement is terminated by Asahi, we have the option to purchase the facility from them. In either case the purchase price is equal to one hundred percent of the then net book value of the facility, as calculated in accordance with GAAP.

In December 2012 construction of the facility was completed, at which time the asset was placed in service. Given our continued involvement in the facility, we were precluded from derecognizing the cost of the facility or the corresponding liability. Therefore, the facility asset, including building and equipment, continued to be recorded within property and equipment, net, on our consolidated balance sheet and depreciated on a straight-line basis over its estimated useful life. The corresponding liability has been divided into two separate components, including a capital lease obligation and deferred revenue, based on their relative fair values at December 2012.

In December 2014, construction of an additional production line within the facility was completed, at which time additional assets were placed into service at a total cost of $6.4 million. Consistent with the facility completed in December 2012, we were precluded from derecognizing the cost of the additional production line or the corresponding liability. Therefore, the asset is being recorded within property and equipment, net, on our consolidated balance sheet and depreciated on a straight-line basis over its estimated useful life. The corresponding liability has been divided into two separate components, including a capital lease obligation and deferred revenue, based on their relative fair values at December 2014 of $3.5 million and $2.9 million, respectively.

The fair value of the capital lease obligation was determined based on the present value of the financing payments due plus the residual value guarantee. The key assumptions used to determine the fair value of this liability included our incremental borrowing rate, the fixed amount per dialyzer payment due to Asahi totaling fifty percent of the cost of the asset paid by Asahi, and the estimated residual value of the assets at the end of the estimated lease term all of which we determined to be Level 3 inputs within the fair value hierarchy. The capital lease obligation has been classified within other long-term liabilities within our consolidated balances sheet with the amount expected to be paid within one year classified within other current liabilities. The capital lease obligation is decreased by payments made to Asahi for dialyzers manufactured for our own use and increased by interest expense.

The fair value of the deferred revenue was determined using cost plus a reasonable margin for contract manufacturing in Germany, Level 3 inputs within the fair value hierarchy. The deferred revenue is recognized in revenues on a straight-line basis over the expected term of the Dialyzer Production Agreement.

The capital lease obligation and deferred revenue balances are $12.7 million and $8.2 million, respectively, at December 31, 2014.

Field Equipment, net

The components of field equipment, net are as follows (in thousands):

	December 31,
	2014			2013
Field equipment	$	61,132		$	49,695
Less accumulated depreciation		(40,014	)		(36,654	)
Field equipment, net	$	21,118		$	13,041

Depreciation expense for field equipment, which is recorded in costs of revenues in the consolidated statements of comprehensive loss, was $4.2 million, $4.0 million and $3.7 million during 2014, 2013 and 2012, respectively.

Deferred Costs of Revenues

Amortization expense of direct costs relating to deferred equipment revenues was $13.5 million, $13.3 million and $13.5 million during 2014, 2013 and 2012, respectively.

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Accrued Expenses, Other Current Liabilities, and Other Long Term Liabilities - Components of Accrued Expenses (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Payroll, compensation and related benefits	$ 12,346	$ 9,041
Distribution expenses	3,069	2,762
General and administrative expenses	3,075	2,207
Audit, legal, and consulting fees	1,394	2,725
Other	4,769	4,290
Total	$ 24,653	$ 21,025

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Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense in Consolidated Statements of Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 12,881	$ 8,638	$ 11,403
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,212	918	1,168
Selling and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	4,442	3,171	4,186
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,726	1,331	1,372
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 5,501	$ 3,218	$ 4,677

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Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies [Line Items]
Minimum purchase commitments	$ 62,300,000
Initial Lease period	11 years
Period for early termination provision of lease	After seven years
Rental description	Two 5-year options to extend beyond the initial term on substantially the same terms and at rent equal to ninety-five percent of the then fair market value
Leasehold improvements allowance	4,300,000		4,300,000
Lease expiry period	2023
Rent expense	3,800,000	2,200,000	2,200,000
NxStage Kidney Care Facility [Member]
Commitments and Contingencies [Line Items]
Lease expiration year start	2018
Lease expiration year end	2022
Foreign Leased Manufacturing Facilities [Member]
Commitments and Contingencies [Line Items]
Lease expiration year start	2015
Lease expiration year end	2018
Minimum [Member]
Commitments and Contingencies [Line Items]
Purchase commitment period	1 year
Minimum [Member] | NxStage Kidney Care Facility [Member]
Commitments and Contingencies [Line Items]
Leasehold improvements allowance	100,000
Period of renewal of options	5 years
Maximum [Member]
Commitments and Contingencies [Line Items]
Purchase commitment period	5 years
Maximum [Member] | NxStage Kidney Care Facility [Member]
Commitments and Contingencies [Line Items]
Leasehold improvements allowance	$ 300,000
Period of renewal of options	10 years

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Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Principles of Consolidation and Basis of Presentation

Principles of Consolidation and Basis of Presentation

The accompanying consolidated financial statements include the accounts of NxStage Medical, Inc. and our wholly-owned and majority-owned subsidiaries. All material intercompany transactions and balances have been eliminated in consolidation.

Use of Estimates

Use of Estimates

The preparation of our consolidated financial statements in conformity with GAAP requires our management to make estimates and assumptions that affect reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Revenue Recognition

Revenue Recognition

We recognize revenue from product sales and services when earned. Revenues are recognized when: (a) there is persuasive evidence of an arrangement, (b) the product has been shipped or services and supplies have been provided to the customer, (c) the sales price is fixed or determinable and (d) collection is reasonably assured.

Certain agreements with distributors allow for product returns and credits. For shipment of product sold to distributors, revenue is recognized at the time of sale if a reasonable estimate of future returns or credit can be made. If a reasonable estimate of future returns or credit cannot be made, we recognize revenue using the “sell-through” method. Under the “sell-through” method, revenue and related costs of revenue is deferred until the final resale of such products to end customers.

In addition to contractually determined volume discounts, in many agreements we offer rebates based on sales to specific end customers and discounts for early payment. Rebates and discounts are recorded as a reduction of sales and trade accounts receivable, based on our best estimate of the amount of probable future rebate or discount on current sales.

We enter into multiple-element arrangements that may include a combination of equipment, related disposables and services. Revenue arrangements with multiple elements are divided into separate units of accounting if specified criteria are met, including whether the delivered element has stand-alone value to the customer, the consideration received is allocated among the separate units based on their respective selling price, and the applicable revenue recognition criteria are applied to each of the separate units.

We determine selling price using vendor specific objective evidence (“VSOE”), if it exists, otherwise third-party evidence of selling price is used. If neither VSOE nor third-party evidence of selling price exists for a unit of accounting, we use best estimated selling price (“BESP”). We generally expect that we will not be able to establish third-party evidence due to the nature of our products and the markets in which we compete, and, as such, we typically will determine selling price using VSOE or BESP.

We determine BESP for an individual element based on consideration of both market and Company-specific factors, including the selling price and profit margin for similar products, the cost to produce the deliverable and the anticipated margin on that deliverable and the characteristics of the varying markets in which the deliverable is sold.

System One Segment

We derive revenue in the home market from the sales of hemodialysis therapy to customers in which the customer either purchases or rents the System One and/or PureFlow SL hardware and purchases a specified number of disposable products and service.

For customers that purchase the System One and PureFlow SL hardware, in the U.S. home market, due to the depot service model whereby equipment requiring service is picked up and a replacement device is shipped to the site of care, we recognize fees received from equipment sale as revenue on a straight-line basis over the expected term of our remaining service obligation and direct costs relating to the delivered equipment are deferred and amortized over the same expected period as the related revenue. Disposable products revenue is recognized on a monthly basis upon delivery.

Under the rental arrangements, revenue is recognized on a monthly basis in accordance with agreed upon contract terms and pursuant to binding customer purchase orders and fixed payment terms.

Our sales arrangements with our international distributors are structured as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms.

In the critical care market, we structure sales of the System One and disposable products as direct product sales and have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Certain of these arrangements provide for training, technical support and extended warranty services to our customers. We recognize training and technical support revenue when the related services are performed. In the case of extended warranty, the service revenue is recognized ratably over the extended warranty period.

In-Center Segment

Our In-Center segment sales are structured as direct product sales primarily through distributors, and we have no significant post delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Some of our distribution contracts for the In-Center segment contain minimum volume commitments with negotiated pricing discounts at different volume tiers. Each agreement may be canceled upon a material breach, subject to certain curing rights, and in many instances minimum volume commitments can be reduced or eliminated upon certain events.

Services Segment

Revenues in our Services segment are derived from dialysis care services provided to patients at our recently opened NxStage Kidney Care dialysis centers.

Revenues are recognized based on a customary fee schedule, net of estimated contractual allowances to reflect the estimated amounts to be received from the payor. Revenues are recognized in the period in which services are provided when we have the ability to reasonably estimate amounts ultimately collectible from the payor. In instances where we do not have the ability to reasonably estimate amounts ultimately collectible, as is often the case with non-contracted commercial health plans and amounts due from patients (including co-pay and deductible amounts), revenue is recognized in the period in which cash is received.

Foreign Currency Translation and Transactions

Foreign Currency Translation and Transactions

Assets and liabilities of our foreign operations are translated into U.S. dollars at current exchange rates, and income and expense items are translated at average rates of exchange prevailing during the year. Foreign exchange gains and (losses) on intercompany loans considered permanent investments are recorded in other comprehensive loss. Gains and (losses) realized from transactions denominated in foreign currencies, including intercompany balances not considered permanent investments, are included in the consolidated statements of comprehensive loss within other (expense) income, net.

Cash and Cash Equivalents

Cash and Cash Equivalents

We consider all highly-liquid investments purchased with original maturities of 90 days or less to be cash equivalents. Cash equivalents include amounts invested in treasury obligation money market funds. Cash equivalents are stated at cost plus accrued interest, which approximates market value.

Concentration of Credit Risk

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk consist principally of cash equivalents, derivatives and accounts receivable. To mitigate such risk, with respect to cash and cash equivalents, we place our cash in bank deposit accounts with financial institutions that have investment grade ratings and capital ratios exceeding minimum Federal Reserve Adequacy Guidelines and in treasury obligation money market funds. To mitigate concentration of credit risk with respect to derivatives we enter into transactions with highly-rated financial institutions and frequently monitor the credit worthiness of our counterparties.

Concentration of credit risk with respect to accounts receivable is primarily limited to certain customers to whom we make substantial sales. Two customers represented 18% and 16% of accounts receivable at December 31, 2014 and one customer represented 19% of accounts receivable at December 31, 2013. To reduce risk, we routinely assess the financial strength of our customers and closely monitor their amounts due and, as a result of our assessment, believe that our accounts receivable credit risk exposure is limited. Historically, we have not experienced any significant credit losses related to an individual customer or group of customers in any particular market or geographic area. We maintain an allowance for doubtful accounts based on an analysis of historical losses from uncollectible accounts, aging of unpaid accounts receivable balances and risks identified for specific customers who may not be able to make required payments. Provisions for the allowance for doubtful accounts are recorded in general and administrative expenses in the accompanying consolidated statements of comprehensive loss.

Activity related to allowance for doubtful accounts consisted of the following (in thousands):

Year Ended	Balance at Beginning of Year		Provision (Recoveries)		Write-offs			Balance at End of Year
December 31, 2014	$	321	$	219	$	(115	)	$	425
December 31, 2013	$	424	$	47	$	(150	)	$	321
December 31, 2012	$	510	$	—	$	(86	)	$	424

We use and are dependent upon a number of single source suppliers of raw materials, components, finished goods and sterilization services. We are dependent on the ability of our suppliers to provide products on a timely basis and on favorable pricing terms. The loss of certain principal suppliers or a significant reduction in product availability from principal suppliers would have a material adverse effect on us, at least in the near term. We believe that our relationships with our suppliers are satisfactory.

Fair Value Measures

Fair Value Measures

Certain financial and non financial assets and liabilities recorded at fair value have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standard. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable such as quoted prices, interest rates and yield curves for similar instruments and model-derived valuations whose inputs are observable. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability.

Derivative Instruments and Hedging

Derivative Instruments and Hedging

Derivative instruments, namely our foreign exchange forward contracts, are recognized on the balance sheet at fair value at the balance sheet date. Changes in the fair value of derivatives that are designated and highly effective as cash flow hedges are deferred in accumulated other comprehensive income (loss) and subsequently recognized in cost of revenues in the same period the hedged items are recognized. The ineffective portion of derivative instruments designated as cash flow hedges, are recorded in other income (expense), net. If the underlying forecasted transaction does not occur, or it becomes probable that it will not occur, the gains and losses on the related derivative instrument are recognized in earnings and any related gains and losses recorded in other comprehensive income (loss) are reclassified into earnings.

Inventory

Inventory

Inventory is stated at the lower of cost, determined using the first-in first-out method (FIFO), or market (net realizable value). We record a provision for any excess or obsolete inventory when warranted based on remaining shelf-life and estimated future demand. We also review our inventory value to determine if it reflects the lower of cost or market based on factors such as inventory items sold at negative gross margins and purchase commitments.

Property and Equipment and Field Equipment

Property and Equipment and Field Equipment

Property and equipment and field equipment are recorded at cost less accumulated depreciation. Depreciation is provided over the estimated useful lives of the related assets using the straight-line method for financial statement purposes. The estimated useful life of our assets are periodically reviewed for reasonableness. Changes in useful lives are accounted for prospectively. Repairs and maintenance are expensed as incurred. When property and equipment are retired, sold or otherwise disposed of, the asset’s carrying amount and related accumulated depreciation are removed from the accounts and any gain or loss is included in operations. When field equipment is sold, the asset’s carrying amount and related accumulated depreciation is removed from the accounts and any gain or loss is deferred and recognized in operations on a straight-line basis over the same period as the related revenues.

We capitalize certain costs, including internal payroll and external direct project costs, incurred in connection with developing or obtaining software designated for internal use. These costs are included in property and equipment and are amortized over the estimated useful lives of the related software.

Construction-in-process is stated at cost, which includes the cost of construction and other direct costs attributable to the construction. No provision for depreciation is made on construction-in-process until such time as the relevant assets are completed and put into use. Construction-in-process at December 31, 2014 and 2013 primarily represents the costs of building, machinery, equipment under installation and software and computer costs.

Field equipment consists of equipment being utilized under disposable-based rental agreements as well as “service pool” equipment. Service pool equipment is equipment owned and maintained by us that are swapped for equipment that need repairs or maintenance by us while being rented or owned by a customer. We record a provision for any excess, lost or damaged equipment when warranted based on an assessment of the equipment in the service pool. Write-downs for equipment are included in distribution expenses.

The estimated useful lives of property and equipment and field equipment are as follows:

	Estimated Useful Life
Buildings	30 years
Manufacturing equipment and tooling	3 to 12 years
Leasehold improvements	Lesser of the lease term (including any renewal periods if appropriate) or estimated useful life of the asset
Computer and office equipment	3 to 5 years
Molds	5 to 7 years
Furniture	5 to 7 years
Field equipment	5 to 7 years

Intangibles and Other Long-Lived Assets

Intangibles and Other Long-Lived Assets

Intangible assets are carried at cost less accumulated amortization. For assets with determinable useful lives, amortization is computed using the straight-line method over the estimated economic lives of the respective intangible assets, ranging from eight to fourteen years. Long-lived assets, including intangible assets, are tested for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. The amount of impairment, if any, is measured based on fair value, which is determined using estimated discounted cash flows to be generated from such assets or group of assets. During 2014, 2013 and 2012, no such impairment was recognized. Assets to be disposed of are reported at the lower of the carrying amount or fair value less selling costs.

Goodwill

Goodwill

Goodwill represents the excess of the cost of an acquired business over the fair value of the related net assets at the date of acquisition. We test goodwill at least annually for impairment, or more frequently when events or changes in circumstances indicate that the goodwill might be impaired. This impairment test is performed annually during the fourth quarter. This test includes first a qualitative assessment and then, if necessary, a quantitative assessment to determine if the fair value of a reporting unit is less than its carrying amount. Factors considered in the qualitative assessment include, but are not limited to, both macroeconomic conditions and entity-specific conditions. For the quantitative assessment the reporting unit’s fair value is estimated using a discounted cash flow or other fair value measurement. Our reporting units with goodwill are our System One and In-center operating segments. During both 2014 and 2012, we utilized the qualitative assessment and concluded that it was more likely than not that the fair value of our reporting units was greater than their carrying value. During 2013, we utilized the quantitative assessment and concluded the fair value of the reporting units exceeds their carrying value, indicating that goodwill was not impaired. We estimated the fair value of our reporting units using a discounted cash flow approach which involves significant judgment with respect to future revenue growth, operating income, capital expenditures, changes in working capital use and the selection of a discount rate.

Stock-Based Compensation

Stock-Based Compensation

Stock-based compensation expense is estimated as of the grant date based on the fair value of the award. We use the Black-Scholes option pricing model to estimate the fair value of stock options and quoted market prices of our common stock to estimate fair value of restricted stock. The expected term is estimated based on the contractual term of each grant and takes into account the historical experience and relevant factors concerning expected exercise and termination behavior of participants. The risk free interest rate for each grant is equal to the U.S. Treasury rate in effect at the time of grant for instruments with an expected life similar to the expected term. The stock volatility assumption is based solely on our historical volatility over the expected term of the award. The dividend yield of zero is based upon the fact that we have not historically granted cash dividends, and do not expect to issue dividends in the foreseeable future.

We recognize stock-based compensation expense over the requisite service period, which generally equals the vesting period, net of forfeitures. Forfeiture rates are estimated based on historical pre-vesting forfeiture history and are updated on a quarterly basis to reflect actual forfeitures of unvested awards and other known events. For awards that vest based on employment, we recognize the associated compensation expense on a straight-line basis. For performance based awards, we recognize expense using the graded vesting methodology based on the number of shares expected to vest. Compensation expense associated with these performance based awards is adjusted quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date the results are determined.

Warranty Costs

Warranty Costs

We accrue estimated costs that we may incur under our product warranty programs at the time the product revenue is recognized, based on contractual rights and historical experience. Warranty expense is included in cost of revenues in the consolidated statements of comprehensive loss. The following is a rollforward of our warranty accrual (in thousands):

Year Ended	Balance at Beginning of Year		Provision		Usage			Balance at End of Year
December 31, 2014	$	297	$	441	$	(451	)	$	287
December 31, 2013	$	324	$	412	$	(439	)	$	297
December 31, 2012	$	380	$	540	$	(596	)	$	324

Distribution Expenses

Distribution Expenses

Distribution expenses are charged to operations as incurred and consist of costs incurred in shipping product to and from customers and the cost of any equipment lost or damaged in the distribution process. Shipping and handling costs billed to customers are included in revenues.

Research and Development Costs

Research and Development Costs

Research and development costs are charged to operations as incurred.

Income Taxes

Income Taxes

We record the tax effect of transactions when such transactions are recorded in our consolidated statement of comprehensive loss. We record a deferred tax asset or liability based on the difference between the financial statement and tax basis of assets and liabilities, as measured by the enacted tax rates. Our provision for income taxes represents the amount of taxes currently payable, if any, plus the change in the amount of net deferred tax assets or liabilities. A valuation allowance is provided against net deferred tax assets if recoverability is uncertain on a more likely than not basis.

We periodically assess our exposures related to our provisions for income taxes and accrue for contingencies that may result in potential tax obligations. For those positions where it is more likely than not that a tax benefit will be sustained, we record the largest amount of tax benefit with a greater than 50 percent likelihood of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, no tax benefit is recognized in the financial statements. We recognize interest and penalties for uncertain tax positions in income tax expense.

We conduct business globally and file income tax returns in the U.S. federal jurisdiction, various states and foreign jurisdictions. We have accumulated significant losses since our inception in 1998. Utilization of the net operating losses may be subject to limitations and certain tax years in the respective tax jurisdictions remain open to examination.

Subsequent Events

Subsequent Events

Events occurring subsequent to December 31, 2014 have been evaluated for potential recognition or disclosure in the consolidated financial statements.

Recent Accounting Pronouncements

Recent Accounting Pronouncements

Effective January 1, 2014, we adopted Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) No. 2013-11, “Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists,” which impacts the presentation of unrecognized tax benefits on the statement of financial position. As a result, unrecognized tax benefits are presented as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. To the extent the tax benefit is not available at the reporting date under the governing tax law or if we do not intend to use the deferred tax asset for such purpose, the unrecognized tax benefit is presented as a liability and not combined with deferred tax assets. The adoption of this standard did not impact our condensed consolidated financial statements, as our practice was consistent with this standard prior to its effective date.

In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers,” which provides guidance for revenue recognition. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The new guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. Early application is not permitted. We are currently assessing the potential impact the adoption of this standard will have on our financial statements.

In August 2014, the FASB issued ASU No. 2014-15, “Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern” (“ASU 2014-15”), which expands upon principles that are currently in U.S. auditing standards by providing guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and by providing related footnote disclosure requirements. The new guidance is effective for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. Early adoption is permitted. We are currently evaluating the impact of this update but it is not expected to have a material impact on our financial statement disclosures.

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Income Taxes - Reconciliation of U.S. Federal Statutory Tax Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Federal statutory rate	34.00%	34.00%	34.00%
Stock compensation	2.00%	(2.50%)	(5.60%)
State income tax, net of federal tax benefit	1.90%	3.20%	2.00%
U.S. research credits	4.10%	11.70%	3.30%
Foreign income inclusion in the U.S.	(2.80%)	(6.70%)	(3.10%)
Valuation allowance	(39.70%)	(40.20%)	(31.40%)
Change in tax reserves		4.00%	(5.60%)
Other, net	(4.90%)	(2.20%)	(0.90%)
Effective tax rate	(5.40%)	1.30%	(7.30%)

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Stock Plans and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Status of Stock Options Granted Under All Plans

A summary of the status of stock options granted under all of our plans at December 31, 2014, and changes during the year then ended, is as follows:

Stock Options	Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value		Average Remaining Contractual  Life
						(In thousands)		(In years)
Outstanding at beginning of year		4,825,880		$	10.73
Granted		997,459		$	14.35
Exercised		(1,524,601	)	$	9.04
Forfeited or expired		(196,313	)	$	15.17
Outstanding at end of year		4,102,425		$	12.02	$	24,832		5.18
Fully vested and exercisable		2,822,955		$	11.30	$	19,264		3.73
Fully vested, exercisable and expected to vest		3,956,565		$	11.96	$	24,197		5.06

Estimated Fair Value of Options at Date of Grant

The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Years Ended December 31,
	2014	2013	2012
Expected life (in years)	4.40 to 5.00	4.50 to 4.70	4.50
Risk-free interest rate	1.56% to 1.69%	0.75% to 1.04%	0.67% to 0.90%
Expected stock price volatility	43% to 45%	62%	70%
Expected dividend yield	—	—	—

Summary of Status of Unvested Restricted Stock Units

The following table summarizes the status of the unvested restricted stock:

	Shares			Weighted  Average Grant-date Fair Value		Aggregate Intrinsic  Value		Weighted  Average Remaining Contractual Life
						(In thousands)		(In years)
Unvested at December 31, 2013		734,221		$	14.72
Granted		699,913		$	14.35
Vested		(192,741	)	$	16.64
Forfeited		(51,548	)	$	13.94
Unvested at December 31, 2014		1,189,845		$	14.23	$	21,334		1.89

Valuation Assumptions for ESPP

The fair value of the employees’ stock purchase rights was estimated using the Black-Scholes option-pricing model with the following assumptions:

	Years Ended December 31,
	2014	2013	2012
Expected life (in months)	6	6	6
Risk-free interest rate	0.07% to 0.10%	0.09% to 0.12%	0.06% to 0.15%
Expected stock price volatility	26.3% to 27.4%	20.1% to 33.6%	23.3% to 36.0%
Expected dividend yield	—	—	—

Summary of Stock-Based Compensation Expense in Consolidated Statements of Comprehensive Loss

The following table presents stock-based compensation expense included in the consolidated statements of comprehensive loss (in thousands):

	Years Ended December 31,
	2014		2013		2012
Cost of revenues	$	1,212	$	918	$	1,168
Selling and marketing		4,442		3,171		4,186
Research and development		1,726		1,331		1,372
General and administrative		5,501		3,218		4,677
Total stock-based compensation expense	$	12,881	$	8,638	$	11,403

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Stockholders' Equity

12 Months Ended

Dec. 31, 2014

Equity [Abstract]

Stockholders' Equity

14. Stockholders’ Equity

We received 196,378, 34,311 and 32,310 shares of common stock that were surrendered in payment for the exercise of stock options during 2014, 2013 and 2012, respectively.

During 2012, we repaid in full all principal and interest in the aggregate amount of $45.2 million under our term loan and security agreement with Asahi through the issuance of 2,456,246 shares of our common stock, which, after the retention by us of 28,351 shares for the payment of certain minimum withholding taxes, resulted in a net issuance to Asahi of 2,427,895 shares.

In connection with the sale of our common stock in a private placement during 2008 we issued warrants to purchase 1,900,000 shares of our common stock. These warrants had an exercise price of $5.50 per share and contained a net share settlement feature. As of December 31, 2013, all warrants had been exercised or had expired.