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.