In postrenal disease, the fractional excretion of sodium (FENa) is usually?

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Multiple Choice

In postrenal disease, the fractional excretion of sodium (FENa) is usually?

FENa shows how well the tubules reclaim sodium. In prerenal states, the kidney conserves Na, so FENa is typically very low (usually <1%). In intrinsic renal disease, tubular damage prevents Na reabsorption, pushing FENa higher (often >2–3%). Postrenal obstruction causes backpressure that lowers GFR and, over time, damages tubules; as tubular reabsorption of Na declines, more Na is lost in urine, causing FENa to rise. While early obstruction can resemble prerenal with a low FENa, established postrenal obstruction commonly yields a FENa above 3%. Thus, postrenal disease is usually associated with a FENa >3%.

FENa shows how well the tubules reclaim sodium. In prerenal states, the kidney conserves Na, so FENa is typically very low (usually <1%). In intrinsic renal disease, tubular damage prevents Na reabsorption, pushing FENa higher (often >2–3%). Postrenal obstruction causes backpressure that lowers GFR and, over time, damages tubules; as tubular reabsorption of Na declines, more Na is lost in urine, causing FENa to rise. While early obstruction can resemble prerenal with a low FENa, established postrenal obstruction commonly yields a FENa above 3%. Thus, postrenal disease is usually associated with a FENa >3%.

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