Renal Failure Index (RFI)
Renal failure index = urine sodium x plasma creatinine / urine creatinine; < 1 favors prerenal azotemia, > 1 favors acute tubular necrosis.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Urine sodium
- 10 mEq/L
- Plasma creatinine
- 4 mg/dL
- Urine creatinine
- 60 mg/dL
Result: Renal failure index 0.67 — favors prerenal azotemia (< 1).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- < 1
- Favors prerenal azotemia.
- > 1
- Favors acute tubular necrosis (UNa x PCr / UCr). Unreliable with diuretics or CKD. A renal index, not a diagnosis.
What you enter
- Urine sodium
- Plasma creatinine
- Urine creatinine
How this is calculated
Espinel CH. The FENa test. Use in the differential diagnosis of acute renal failure. JAMA. 1976;236(6):579-581. (Renal failure index; Miller TR, et al. Ann Intern Med. 1978.) Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.