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  Fractional Excretion of Sodium (FENa)

Urine Na  
Serum Na  
Urine Cr  
Serum Cr  

FE Na  
Decimal Precision  

Include literature references: Yes   No
  • 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


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

Associated Logical Observation Identifiers Names and Codes [LOINC]
Parameter LOINC's and Suggested Units
Urine Na 2955-3 : mEq/L      35678-2 : mEq/L      2955-3 : mmol/L      35678-2 : mmol/L      
Serum Na 2951-2 : mmol/L      2947-0 : mEq/L      32340-2 : mEq/L      39791-9 : mEq/L      
Urine Cr 35674-1 : mg/dL      2161-8 : mg/dL      14683-7 : mmol/L      
Serum Cr 2160-0 : mg/dL      38483-4 : mg/dL      14682-9 : mcmol/L      22726-4 : mcmol/L      59826-8 : mcmol/L      
FE Na 49135-7 : %      

This material contains content from LOINC® (http://loinc.org). The LOINC table, LOINC codes, and LOINC panels and forms file are copyright © 1995-2014, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee and available at no cost under the license at http://loinc.org/terms-of-use.

Associated ICD10-CM Codes
   N17.2Acute kidney failure with medullary necrosis
   N19Unspecified kidney failure
   N25.9Disorder resulting from impaired renal tubular function, unspecified
   N17.9Acute kidney failure, unspecified

Associated ICD9-CM Codes
   584.9Acute renal failure nos
   588.8Impaired renal funct nec
   588.9Impaired renal funct nos
   586Renal failure nos
   583.7Nephr nos/medull necros

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