FENa Calculator — Fractional Excretion of Sodium
Compute the fractional excretion of sodium (FENa) to help separate pre-renal acute kidney injury from intrinsic tubular injury (acute tubular necrosis).
When to use it
Use in oliguric acute kidney injury. FENa below 1 percent suggests a pre-renal cause; above 2 percent suggests acute tubular necrosis. Diuretics invalidate FENa — use fractional excretion of urea instead.
Formula
FENa (percent) = (urine sodium x plasma creatinine) / (plasma sodium x urine creatinine) x 100.
Category
Acute Kidney Injury
References
- Espinel CH. The FENa test. Use in the differential diagnosis of acute renal failure. JAMA. 1976;236:579-581.
About NephroMind
This calculator is part of NephroMind, a free clinical decision-aid platform from the Arab Society of Nephrology and Renal Transplantation (ASNRT) — over 128 bedside nephrology calculators plus a renal drug-dosing database, coded by a practicing transplant nephrologist.