Fractional Excretion of Sodium (SI units)

 

Input
 

Urine Na		mcmol/L mmol/L
Serum Na		mcmol/L mmol/L
Urine Cr		mcmol/L mmol/L
Serum Cr		mcmol/L mmol/L

 

Result
 

FENa		% fraction ratio
Decimal Precision   0 1 2 3

 

Notes

• For this caculation, the Urine Cr is entered as mcmol/L by default. Change the unit selector if you have a value in mmol/L.
• 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.

 
Equations used
 

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

 

 

References

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