renal failure index (RFI), an assessment of acute renal failure that compares the sodium clearance with the creatinine clearance: RFI |m= UNa UCr/PCr, where PCr |m= plasma concentration of creatinine, UCr |m= urinary concentration of creatinine, and UNa |m= urinary concentration of sodium. A value below 1.0 indicates renal failure because of prerenal azotemia, and a value above 2.0 suggests that it is caused by acute tubular necrosis.
