ToolsCalculators
Fractional excretion of urea (FEUrea)
Prerenal vs intrinsic AKI, valid after diuretics.
Fractional excretion of urea (FEUrea)
Urine urea nitrogen
mg/dL
Serum urea nitrogen (BUN)
mg/dL
Urine creatinine
mg/dL
Serum creatinine
Complete the fields above to see the result.
When to use
- Distinguishing prerenal azotaemia from intrinsic renal failure, especially when the patient has received diuretics (which invalidate FENa).
Formula
FEUrea = (urine urea x serum creatinine) / (serum urea x urine creatinine) x 100. Units cancel, so use any consistent unit for each pair.
Pearls and pitfalls
- More reliable than FENa in diuretic-treated patients because urea handling is less affected by loop and thiazide diuretics.