Although conventional hemodialysis removes waste products and corrects fluid imbalance, it does not replace critical absorptive, metabolic, endocrine, and immunologic functions performed by healthy renal tubule cells. This trial involving patients with acute renal failure evaluates the efficacy and safety of an extracorporeal renal assist device (RAD) containing human renal tubule cells connected to a conventional hemodialysis circuit. It is hypothesized that short-term (72-h) use of this cell therapeutic device will improve survival of ARF patients compared to patients receiving only conventional continuous renal replacement therapy.

Acute Renal Failure (ARF) is a severe inflammatory disease state often accompanied by Multi-Organ Failure (MOF) and Systemic Inflammatory Response Syndrome (SIRS). ARF is precipitated by many factors and is most often linked to the loss of kidney tubule cell function. Patients with ARF are treated in the intensive care units of hospitals, and recovery of renal function is vitally important to their survival. Current therapy for ARF involves conventional kidney support with continuous renal replacement therapies (CRRT). Despite advances in treating patients with CRRT, ARF has an extremely high mortality rate (55-70%) and requires extensive hospital stays, predominantly in the ICU. The RAD is designed to both treat ARF with MOF and/or SIRs and facilitate the natural recovery of a patient's own kidney function. The RAD is intended for use for short periods of time in conventional extracorporeal therapeutic systems that are already available in the hospital. The RAD therapy operates outside the body and is designed to mimic the structure and function of the natural kidney. In this manner it is intended to replace the missing metabolic, endocrine, and immunologic functions of the kidney and allow time for the patient's own kidneys to resume normal functions.

Inclusion Criteria:

• Non-pregnant.
• Requiring continuous renal replacement therapy for treatment of acute renal failure secondary to acute tubular necrosis in ICU setting.
• At least one non-renal organ failure or presence of sepsis.

Exclusion Criteria:

• Contraindications to systemic anticoagulation with heparin.
• Irreversible brain damage.
• Presence of any organ transplant.
• Presence of preexisting chronic renal failure prior to this episode of acute renal failure.
• Acute renal failure occurring in the setting of burns, obstructive uropathy, allergic interstitial nephritis, acute or rapidly progressive glomerulonephritis, vasculitis, hemolytic-uremic syndrome, thrombotic thrombocytopenic purpura (TTP), malignant hypertension, scleroderma renal crisis, atheroembolism, functional or surgical nephrectomy, hepatorenal syndrome, cyclosporine or tacrolimus nephrotoxicity.
• Metastatic malignancy which is actively being treated or may be treated by chemotherapy or radiation during the subsequent three month period after RAD therapy.
• Chronic immunosuppression.
• Receiving Xigris therapy at time of randomization.
• Severe liver failure as documented by a Pugh Liver Failure Score.
• Do Not Resuscitate (DNR) status.
• Platelet count 35,000/mm3 within 4 hours of platelet transfusion.
• Patient not expected to survive 28-days because of an irreversible medical condition.
• Any medical condition that the investigator thinks may interfere with the study objectives.
• Concurrent enrollment in another clinical trial that could affect the outcome of this study protocol.
• Use of any other Investigational drug or device within the previous 30 days.