Fractional Excretion of Urea (FEUrea)

Differentiate prerenal from intrinsic AKI when patient is on diuretics. FEUrea < 35% suggests prerenal; > 50% suggests intrinsic AKI.

For educational and clinical reference. Not a substitute for medical judgment. See the medical disclaimer.
FEUrea
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Interpretation
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References

  1. Carvounis CP, Nisar S, Guro-Razuman S. Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Kidney Int. 2002;62(6):2223-2229.

How to use

  1. Enter urine and plasma urea and creatinine.
  2. FEUrea and interpretation update instantly.
  3. Use the copy button to copy results.

Frequently asked questions

When should I use FEUrea instead of FENa?

FEUrea is preferred over FENa in patients on diuretics, since diuretics increase urinary sodium and falsely elevate FENa.

How is FEUrea calculated?

FEUrea (%) = (Urine Urea × Plasma Cr) / (Plasma Urea × Urine Cr) × 100.

What thresholds matter?

FEUrea < 35% suggests prerenal AKI; > 50% suggests intrinsic AKI (ATN). Values between are indeterminate.

Is FEUrea always reliable?

FEUrea has limitations and should be interpreted alongside the clinical picture, urinalysis, and FENa where applicable.

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