Fractional excretion of sodium (FeNa) is used to distinguish prerenal from intrinsic AKI. Which FeNa value suggests prerenal AKI?

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Multiple Choice

Fractional excretion of sodium (FeNa) is used to distinguish prerenal from intrinsic AKI. Which FeNa value suggests prerenal AKI?

FeNa measures how much filtered sodium the kidneys excrete in the urine. In prerenal AKI, reduced blood flow to the kidneys causes the tubules to avidly reabsorb sodium to conserve volume, so urinary sodium is low and the fractional excretion of sodium stays very low—typically under 1%. In intrinsic AKI, like tubular injury, the reabsorptive ability is impaired, so more sodium is lost in urine and FeNa is higher, usually above 2%. So a FeNa less than 1% best points to prerenal AKI.

FeNa measures how much filtered sodium the kidneys excrete in the urine. In prerenal AKI, reduced blood flow to the kidneys causes the tubules to avidly reabsorb sodium to conserve volume, so urinary sodium is low and the fractional excretion of sodium stays very low—typically under 1%. In intrinsic AKI, like tubular injury, the reabsorptive ability is impaired, so more sodium is lost in urine and FeNa is higher, usually above 2%. So a FeNa less than 1% best points to prerenal AKI.

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