Fractional sodium excretion

The fractional sodium (FE _Na ) indicates how much of the sodium, which in the renal corpuscles (glomeruli) as part of the primary urine is actually excreted was filtered at the end of the urine. The rest is absorbed into the blood again in the kidneys together with other substances that are still required.

${\displaystyle FE_{Na}={U_{Na}\times P_{Krea} \over P_{Na}\times U_{Krea}}}$

U _Na : urinary sodium

P _Na : plasma sodium

U _Krea : urinary creatinine

P _Krea : plasma creatinine

Use in the context of the differential diagnosis of acute kidney failure (however limited usability after the use of diuretics , which is why in this case fractional urea excretion leads to more precise results):

FE Na <1%:	prerenal kidney failure (retention of sodium and thus water)
FE Na > 2%:	renal kidney failure (decreased ability of the kidneys to concentrate)

literature

Lameire N. Acute renal failure. Lancet 2005; 365: 417-430

See also

Fractional urea excretion , dose adjustment in renal insufficiency .

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !