Nephrology

Fractional Excretion of Urea (FEUrea)

Differentiates prerenal vs intrinsic acute kidney injury.

Parameters

mg/dL
mg/dL
mg/dL
mg/dL

Fractional Excretion of Urea (FEUrea) Result

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FormulaFEUrea = (Urine Urea × Serum Creatinine) / (Serum BUN × Urine Creatinine) × 100%

Clinical Pearls

Urea transport in the kidneys is relatively unaffected by diuretic therapy, making FEUrea highly superior to FeNa for diagnosing the cause of AKI in patients actively taking loop diuretics (e.g., Furosemide).

Limitations

May be inaccurate in patients taking osmotic diuretics, or those with severe hypercatabolism or upper GI bleeding (which independently raises BUN).