renal failure index (RFI)

Introduction

Defined as:

 (urine Na+  x urine creatinine) / urine creatinine

Indications

• acute renal failure
  • prerenal azotemia
  • acute tubular necrosis

Clinical significance

• useful for distinguishing prerenal azotemia from intrinsic renal disease in patients with acute renal failure (ARF):
• index (RFI)
  • < 0.01 (or 1%): prerenal
  • > 0.01 (or 1%): renal

More general terms

• urinary indices