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 FE Na+  



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Author3 Posts
  #1

what is fractional excretion of sodium?

what are the differences between pre renal and renal failure?




  #2

Fractional excretion of sodium is excreted load of sodium divided by filtered load of sodium or to put it in other way
FeNa+ = (V X UNa+) / (GFR X PNa+) where V is urine flow rate and PNa+ and UNa+ are plasma and urine Na+ conc.

In pre-renal failure due to decreased renal perfusion the kidneys try to conserve as much sodium so as to increase plasma volume and hence renal perfusion. So FENa+ will be less in pre-renal failure compared to intrinsic renal failure. I don't remember the values though.


  #3

thanks good explanation..FENa+ less than 1%is typical of pre-renal failure..
in renal (ATN)FENa+ is greater than 2% due to failure to reabsorb





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