Fractional Excretion of Urea FeUrea Calculator

Fractional Excretion of Urea FeUrea Explanation and Clinical Context Fractional Excretion of Urea FeUrea estimates the percentage of filtered urea that is excreted in urine. The calculation uses urine urea concentration serum urea concentration urine creatinine concentration and serum creatinine concentration. The formula is FeUrea equals Uurea times Scr divided by Surea times Ucr multiplied by 100 percent.

FeUrea complements other urine indices for differential diagnosis of azotemia in patients with acute kidney injury. It is particularly useful when diuretics have been administered because FeUrea is less affected by diuretic use than fractional excretion of sodium. Clinically FeUrea values less than 35 percent are commonly interpreted as consistent with prerenal azotemia in the appropriate clinical setting while values equal to or above 35 percent suggest intrinsic renal tubular injury.

Interpretation must always consider clinical context urine sediment and trends in renal function. Reference Bennett M et al. Use of fractional excretion of urea in the evaluation of acute kidney injury.

Clinical Nephrology publications and review articles provide further discussion of cutoff values and limitations. Please consult primary nephrology literature for detailed evidence and guidance.