GUARANTY

Exhibit 10.2

GUARANTY

FOR VALUE RECEIVED, the sufficiency of which is hereby acknowledged, and in consideration of credit and/or financial accommodation heretofore or hereafter from time to time made or granted to C.P. ATLAS ACQUISITION CORP. (the “Borrower”) which shall be merged with and into AMERICAN RENAL HOLDINGS INC. (the “Company”) on the Closing Date by BANK OF AMERICA, N.A. (the “Administrative Agent”) and the other Secured Parties, the undersigned Guarantors (whether one or more the “Guarantor”, and if more than one jointly and severally) hereby furnishes its guaranty of the Guaranteed Obligations (as hereinafter defined) as set forth below.

Reference is made to that certain Credit Agreement dated as of May 7, 2010 (as amended, supplemented or otherwise modified from time to time, the “Credit Agreement”) among the Borrower, Bank of America, N.A., as Administrative Agent, Swing Line Lender and L/C Issuer, each lender from time to time party thereto (the “Lenders”) and the other parties thereto. Capitalized terms used and not defined herein (including, without limitation, the term “Obligations”, as used in Section 1 and elsewhere herein) are used with the meanings assigned to such terms in the Credit Agreement.

1. Guaranty. The Guarantor hereby absolutely and unconditionally guarantees, as a guaranty of payment and performance and not merely as a guaranty of collection, prompt payment when due, whether at stated maturity, by required prepayment, upon acceleration, demand or otherwise, and at all times thereafter, of any and all of the Obligations whether for principal, interest, premiums, fees, indemnities, damages, costs, expenses or otherwise, of the Borrower to the Secured Parties, and whether arising under the Credit Agreement or under any other Loan Document, or under any Secured Cash Management Agreement or any Secured Hedge Agreement (including all renewals, extensions, amendments, refinancings and other modifications thereof and all costs, attorneys’ fees and expenses incurred by the Secured Parties in connection with the collection or enforcement thereof), and whether recovery upon such indebtedness and liabilities may be or hereafter become unenforceable or shall be an allowed or disallowed claim under any proceeding or case commenced by or against the Guarantor or the Borrower under the Debtor Relief Laws, and including interest that accrues after the commencement by or against the Borrower of any proceeding under any Debtor Relief Laws (collectively, the “Guaranteed Obligations”). The Administrative Agent’s books and records showing the amount of the Guaranteed Obligations shall be admissible in evidence in any action or proceeding, and shall be binding upon the Guarantor for the purpose of establishing the amount of the Guaranteed Obligations and conclusive absent manifest error. This Guaranty shall not be affected by the genuineness, validity, regularity or enforceability of the Guaranteed Obligations or any instrument or agreement evidencing any Guaranteed Obligations, or by the existence, validity, enforceability, perfection, non-perfection or extent of any collateral therefor, or by any fact or circumstance relating to the Guaranteed Obligations which might otherwise constitute a defense (other than a defense of payment in full of the Guaranteed Obligations) to the obligations of the Guarantor under this Guaranty, and the Guarantor hereby irrevocably waives any defenses it may now have or hereafter acquire in any way relating to any or all of the foregoing.

2. Rights of Lenders. The Guarantor consents and agrees that the Secured Parties may, at any time and from time to time, without notice or demand, and without affecting the enforceability or continuing effectiveness hereof: (a) amend, extend, renew, compromise, discharge, accelerate or otherwise change the time for payment or the terms of the Guaranteed Obligations or any part thereof; (b) take, hold, exchange, enforce, waive, release, fail to perfect, sell, or otherwise dispose of any security for the payment of this Guaranty or any Guaranteed Obligations; (c) apply such security and direct the order or manner of sale thereof as the Administrative Agent, the L/C Issuer and the Lenders in their sole discretion may determine; and (d) release or substitute one or more of any endorsers or other guarantors of any of the Guaranteed Obligations. Without limiting the generality of the foregoing, the Guarantor consents to the taking of, or failure to take, any action which might in any manner or to any extent vary the risks of the Guarantor under this Guaranty or which, but for this provision, might operate as a discharge of the Guarantor.

3. Certain Waivers. The Guarantor waives (a) any defense arising by reason of any disability or other defense of the Borrower or any other guarantor, or the cessation from any cause whatsoever (including any act or omission of any Secured Party) of the liability of the Borrower; (b) any defense based on any claim that the Guarantor’s obligations exceed or are more burdensome than those of the Borrower; (c) the benefit of any statute of limitations affecting the Guarantor’s liability hereunder; (d) any right to proceed against the Borrower, proceed against or exhaust any security for the Guaranteed Obligations, or pursue any other remedy in the power of any Secured Party whatsoever; (e) any benefit of and any right to participate in any security now or hereafter held by any Secured Party; and (f) to the fullest extent permitted by law, any and all other defenses or benefits that may be derived from or afforded by applicable law limiting the liability of or exonerating guarantors or sureties. The Guarantor expressly waives all setoffs and counterclaims and all presentments, demands for payment or performance, notices of nonpayment or nonperformance, protests, notices of protest, notices of dishonor and all other notices or demands of any kind or nature whatsoever with respect to the Guaranteed Obligations, and all notices of acceptance of this Guaranty or of the existence, creation or incurrence of new or additional Guaranteed Obligations.

4. Obligations Independent. The obligations of the Guarantor hereunder are those of primary obligor, and not merely as surety, and are independent of the Guaranteed Obligations and the obligations of any other guarantor, and a separate action may be brought against the Guarantor to enforce this Guaranty whether or not the Borrower or any other person or entity is joined as a party.

5. Subrogation. The Guarantor shall not exercise any right of subrogation, contribution, indemnity, reimbursement or similar rights with respect to any payments it makes under this Guaranty until all of the Guaranteed Obligations and any amounts payable under this Guaranty (other than obligations and liabilities under Secured Cash Management Agreements and Secured Hedge Agreements) have been paid and performed in full in cash and the Commitments and the Facility are terminated. If any amounts are paid to the Guarantor in violation of the foregoing limitation, then such amounts shall be held in trust for the benefit of the Secured Parties and shall forthwith be paid to the Secured Parties to reduce the amount of the Guaranteed Obligations, whether matured or unmatured.

6. Termination; Reinstatement. This Guaranty is a continuing and irrevocable guaranty of all Guaranteed Obligations now or hereafter existing and shall remain in full force and effect until all Guaranteed Obligations and any other amounts payable under this Guaranty (other than obligations and liabilities under Secured Cash management Agreements and Secured Hedge Agreements) are paid in full in cash and the Commitments are terminated. Notwithstanding the foregoing, this Guaranty shall continue in full force and effect or be revived, as the case may be, if any payment by or on behalf of the Borrower or the Guarantor is made, or any of the Secured Parties exercises its right of setoff, in respect of the Guaranteed Obligations and such payment or the proceeds of such setoff or any part thereof is subsequently invalidated, declared to be fraudulent or preferential, set aside or required (including pursuant to any settlement entered into by any of the Secured Parties in their discretion) to be repaid to a trustee, receiver or any other party, in connection with any proceeding under any Debtor Relief Laws or otherwise, all as if such payment had not been made or such setoff had not occurred and whether or not the Secured Parties are in possession of or have released this Guaranty and regardless of any prior revocation, rescission, termination or reduction. The obligations of the Guarantor under this paragraph shall survive termination of this Guaranty.

7. Subordination. The Guarantor hereby subordinates the payment of all obligations and indebtedness of the Borrower owing to the Guarantor, whether now existing or hereafter arising, including but not limited to any obligation of the Borrower to the Guarantor as subrogee of the Secured Parties or resulting from the Guarantor’s performance under this Guaranty, to the payment in full in cash of all Guaranteed Obligations (other than obligations and liabilities under Secured Cash Management Agreements and Secured Hedge Agreements). If the Secured Parties so request, any such obligation or indebtedness of the Borrower to the Guarantor shall be enforced and performance received by the Guarantor as trustee for the Secured Parties and the proceeds thereof shall be paid over to the Secured Parties on account of the Guaranteed Obligations, but without reducing or affecting in any manner the liability of the Guarantor under this Guaranty.

8. Stay of Acceleration. In the event that acceleration of the time for payment of any of the Guaranteed Obligations is stayed, in connection with any case commenced by or against the Guarantor or the Borrower under any Debtor Relief Laws, or otherwise, all such amounts shall nonetheless be payable by the Guarantor immediately upon demand by the Secured Parties.

9. Expenses. The Guarantor shall pay all reasonable and invoiced out-of-pocket expenses incurred by the Administrative Agent, any Lender or the L/C Issuer (including the reasonable and invoiced fees, charges and disbursements of any one counsel for the Administrative Agent, any Lender or the L/C Issuer, taken as a whole, and, if necessary, of one local counsel in any jurisdiction and one regulatory counsel in any jurisdiction), in connection with the enforcement or protection of its rights under this Guaranty. The agreements in this paragraph shall survive the resignation of the Administrative Agent, the L/C Issuer and the Swing Line Lender, the replacement of any Lender, the termination of the Guaranty and the repayment, satisfaction or discharge of all the other Guaranteed Obligations

10. Miscellaneous. No provision of this Guaranty may be waived, amended, supplemented or modified, except by a written instrument executed by the Administrative Agent

and the Guarantor (with the consent of the Lenders or the Required Lenders if required under the Credit Agreement). No failure by Administrative Agent to exercise, and no delay in exercising, any right, remedy or power hereunder shall operate as a waiver thereof; nor shall any single or partial exercise of any right, remedy or power hereunder preclude any other or further exercise thereof or the exercise of any other right, power or remedy. The remedies herein provided are cumulative and not exclusive of any remedies provided by law or in equity. The unenforceability or invalidity of any provision of this Guaranty shall not affect the enforceability or validity of any other provision herein. Unless otherwise agreed by the Administrative Agent and the Guarantor in writing, this Guaranty is not intended to supersede or otherwise affect any other guaranty now or hereafter given by the Guarantor for the benefit of the Secured Parties or any term or provision thereof.

11. Guarantor Supplements. Upon the execution and delivery by any Person of a Guaranty Supplement substantially in the form attached hereto as Exhibit A (a “Guarantor Supplement”), (a) such Person shall be referred to as an “Additional Guarantor” and shall become and be a Guarantor hereunder, and each reference in this Guaranty to a “Guarantor” shall also mean and be a reference to such Additional Guarantor, and each reference in any other Loan Document to a “Guarantor” shall also mean and be a reference to such Additional Guarantor, and (b) each reference herein to “this Guaranty”, “hereunder”, “hereof” or words of like import referring to this Guaranty, and each reference in any other Loan Document to the “Guaranty”, “thereunder”, “thereof” or words of like import referring to this Guaranty, shall mean and be a reference to this Guaranty as supplemented by such Guaranty Supplement.

12. Other Guarantors. To the extent that any Guarantor shall be required hereunder to pay a portion of the Guaranteed Obligations exceeding the greater of (a) the amount of the economic benefit actually received by such Guarantor from the Loans and (b) the amount such Guarantor would otherwise have paid if such Guarantor had paid the aggregate amount of the Guaranteed Obligations (excluding the amount thereof repaid by the Borrower) in the same proportion as such Guarantor’s net worth at the date enforcement is sought hereunder bears to the aggregate net worth of all the Guarantors (taken together with the aggregate net worth of all other “Guarantors” (as such term is defined in the Credit Agreement) obligated with respect to the Guaranteed Obligations (the “Other Guarantors”)) at the date of enforcement is sought hereunder, then each Other Guarantor shall reimburse such other Guarantors for the amount of such excess, pro rata, based on the respective net worths of such Other Guarantors at the date enforcement hereunder is sought.

13. Condition of Borrower. The Guarantor acknowledges and agrees that it has the sole responsibility for, and has adequate means of, obtaining from the Borrower and any other guarantor such information concerning the financial condition, business and operations of the Borrower and any such other guarantor as the Guarantor requires, and that none of the Secured Parties has any duty, and the Guarantor is not relying on the Secured Parties at any time, to disclose to the Guarantor any information relating to the business, operations or financial condition of the Borrower or any other guarantor (the Guarantor waiving any duty on the part of the Secured Parties to disclose such information and any defense relating to the failure to provide the same).

14. Setoff. If and to the extent any payment is not made when due hereunder, the Administrative Agent may setoff and charge from time to time any amount so due against any or all of the Guarantor’s accounts or deposits with the Administrative Agent.

15. Representations and Warranties. Each of the representations set forth in Credit Agreement set forth in Sections 5.01, 5.02, 5.03 and 5.04 of the Credit Agreement, insofar as they relate directly to any Guarantor, are true and correct in all material respects on and as of the Closing Date with the same effect as though made on and as of such date, except to the extent such representations and warranties expressly relate to an earlier date, in which case they shall be true and correct in all material respects as of such earlier date.

16. Indemnification and Survival. Without limitation on any other obligations of the Guarantor or remedies of the Administrative Agent under this Guaranty, the Guarantor shall, to the fullest extent permitted by law, indemnify, defend and save and hold harmless the Secured Parties from and against, and shall pay on demand, any and all damages, losses, liabilities and expenses (including attorneys’ fees and expenses and the allocated cost and disbursements of internal legal counsel) that may be suffered or incurred by the Secured Parties in connection with or as a result of any failure of any Guaranteed Obligations to be the legal, valid and binding obligations of the Borrower enforceable against the Borrower in accordance with their terms. The obligations of the Guarantor under this paragraph shall survive the payment in full of the Guaranteed Obligations and termination of this Guaranty.

17. GOVERNING LAW. THIS GUARANTY SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

18. SUBMISSION TO JURISDICTION. THE GUARANTOR IRREVOCABLY AND UNCONDITIONALLY SUBMITS, FOR ITSELF AND ITS PROPERTY, TO THE NONEXCLUSIVE JURISDICTION OF THE COURTS OF THE STATE OF NEW YORK SITTING IN NEW YORK COUNTY AND OF THE UNITED STATES DISTRICT COURT OF THE SOUTHERN DISTRICT OF NEW YORK, AND ANY APPELLATE COURT FROM ANY THEREOF, IN ANY ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS GUARANTY, OR FOR RECOGNITION OR ENFORCEMENT OF ANY JUDGMENT, AND EACH OF THE PARTIES HERETO IRREVOCABLY AND UNCONDITIONALLY AGREES THAT ALL CLAIMS IN RESPECT OF ANY SUCH ACTION OR PROCEEDING MAY BE HEARD AND DETERMINED IN SUCH NEW YORK STATE COURT OR, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, IN SUCH FEDERAL COURT. EACH OF THE PARTIES HERETO AGREES THAT A FINAL JUDGMENT IN ANY SUCH ACTION OR PROCEEDING SHALL BE CONCLUSIVE AND MAY BE ENFORCED IN OTHER JURISDICTIONS BY SUIT ON THE JUDGMENT OR IN ANY OTHER MANNER PROVIDED BY LAW. NOTHING IN THIS GUARANTY SHALL AFFECT ANY RIGHT THAT THE ADMINISTRATIVE AGENT, ANY LENDER OR THE L/C ISSUER MAY OTHERWISE HAVE TO BRING ANY ACTION OR PROCEEDING RELATING TO THIS GUARANTY AGAINST THE GUARANTOR OR ITS PROPERTIES IN THE COURTS OF ANY JURISDICTION.

19. WAIVER OF VENUE. THE GUARANTOR IRREVOCABLY AND UNCONDITIONALLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY

APPLICABLE LAW, ANY OBJECTION THAT IT MAY NOW OR HEREAFTER HAVE TO THE LAYING OF VENUE OF ANY ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS GUARANTY IN ANY COURT REFERRED TO IN SECTION 18. EACH OF THE PARTIES HERETO HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, THE DEFENSE OF AN INCONVENIENT FORUM TO THE MAINTENANCE OF SUCH ACTION OR PROCEEDING IN ANY SUCH COURT.

20. SERVICE OF PROCESS. EACH PARTY HERETO IRREVOCABLY CONSENTS TO SERVICE OF PROCESS IN THE MANNER PROVIDED FOR NOTICES IN SECTION 11.02 OF THE CREDIT AGREEMENT. NOTHING IN THIS GUARANTY WILL AFFECT THE RIGHT OF ANY PARTY HERETO TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED BY APPLICABLE LAW.

21. WAIVER OF JURY TRIAL. EACH PARTY HERETO HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY IN ANY LEGAL PROCEEDING DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING TO THIS GUARANTY OR THE TRANSACTIONS CONTEMPLATED HEREBY (WHETHER BASED ON CONTRACT, TORT OR ANY OTHER THEORY). EACH PARTY HERETO (A) CERTIFIES THAT NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY OTHER PERSON HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PERSON WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER AND (B) ACKNOWLEDGES THAT IT AND THE OTHER PARTIES HERETO HAVE BEEN INDUCED TO ENTER INTO THIS GUARANTY BY, AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION.

Executed as of the date first written above.