Fractional Excretion of Urea (FEUrea)

Fractional Excretion of Urea (FEUrea)
mg/dL
mg/dL
mg/dL
mg/dL
Determines the cause of renal failure. Similar to the FENa, but can be used on patients on diuretics.

Formula

Fractional Excretion of Urea (FEUrea) = (Serum Cr * U Urea ) / (Serum Urea x U Cr ) %

Pearls / Pitfalls

While lesser known than FENa, the FEUrea can be used in patients on diuretics, since urea excretion is not significantly affected by diuretics.

Management

In patients with acute kidney and suspected obstructive uropathy, consider bedside ultrasound to evaluate for hydronephrosis, bladder distention, etc. Empiric Foley catheter placement may also be valid in some settings, though it may also be associated with complications, and does not rule out ureteral obstructions above the bladder.

More Information

This test can provide similar information to the FENa equation, but can still be used in patients on diuretic therapy (diuretics alter the sodium concentration, making the FENa equation unusable). Prerenal Intrinsic renal Postrenal FENa <1% >1% >4% FEUrea ≤ 35% >50% N/A

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