🫘 Fractional Excretion of Urea (FEUrea)
Differentiate pre-renal AKI from ATN with the fractional excretion of urea (FEUrea).
Fractional Excretion of Urea (FEUrea)
Urine urea (mg/dL)
Serum urea (BUN) (mg/dL)
Urine creatinine (mg/dL)
Serum creatinine (mg/dL)
When to use
Assess acute kidney injury, especially after diuretics.
How it works
FEUrea = (urine urea × serum creatinine) / (serum urea × urine creatinine) × 100. < 35% pre-renal; > 50% intrinsic.
Key points
- More reliable than FENa when diuretics have been given.
- Urea handling is less affected by diuretics.
- Interpret with clinical context and urine microscopy.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.