Fractional Excretion of Sodium

 
FENa = (UrineNa / SerumNa) / (UrineCr / SerumCr) * 100

 
Input:
 
Urine Na  
Serum Na  
Urine Cr  
Serum Cr  

 
Result:
 
FENa  
 
Decimal Precision  
 
Notes
  • In this calculator, mcg is the abbreviation for micrograms.
  • The FENa helps differentiate acute tubular necrosis from a prerenal state.
  • FENa >2 % usually indicates ATN.
  • FENa <1% usually indicates a prerenal state such as dehydration or other forms of prerenal azotemia.
  • FENa's between 1% and 2% may be seen with either ATN or prerenal state.

 
References
  1. Stein JH, ed. Internal Medicine. 4th edition. Mosby-Year Book. 1994. NLMN ID: 9309759 NCBI Logo

 

 
 
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