Fractional Excretion of Urea =

((Urine Urea/Plasma Urea)*100
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(Urine Creatinine/Plasma Creatinine))

FE Urea is used to determine the type of renal failure in patients using diuretics, since the FeNa calculation can be inaccurate. Fractional excretion of urine less than 35% is consistent with a pre-renal acute renal failure. (1,2)

Related: FeNa Calculator

Sources:
1. E-medicine: Acute Renal Failure
2. Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Carvounis CP, Nisar S, Guro-Razuman S.

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