Sodium, Fractional Excretion

Abbrev Code:FENA   
Order Code:LAB3469Order Name:Fractional Excretion of Sodium
Order Instructions:Plasma Na and Creat must be ordered separately.
Synonyms:Fractional Excretion of Sodium; FENA
Methodology:Calculation of FENA based on urine and blood sodium and creatinine.
CPT Codes: 84300 x1, 84300 x1, 82570 x1, 82570 x1
Test Includes:Urinary sodium and creatinine; blood sodium and creatinine must be collected within 6 hours (before or after).
Turnaround Time:Performed and reported 24 hours/day.
Associated Links:

Urine Collection Procedure, Roche Go Live Schedule

Collection Instructions

Specimen:Random urine specimen collected within 6 hours of blood specimen.
Optimal Volume:Submit entire urine collection (analysis requires 0.2 mL) in plastic leakproof container.
Container:Plastic leakproof container, sterile

Processing and Shipping

Specimen Processing:Mix urine collection well before aliquot is taken; aliquot 1.25 mL, 0.2 mL minimum. Store in refrigerator.
Shipping Instructions:Ship at refrigerated temperature.
Stability:Roche: 2 days at room temperature; 6 days refrigerated; 6 months frozen.
Test Performed at or Referral Lab Chemistry  (Roche-Grand Itasca, Roche-Lakes, Roche-Northland, Roche-Ridges, Roche-Southdale, Roche-St. John's, Roche-UMMC East, Roche-UMMC West)


Reference Range:



Prerenal Azotemia

Acute Tubular Necrosis


less than 2.5%

greater than 2.5%


less than 1%

greater than 3%



Use:Evaluate suspected renal diseases that affect sodium clearance.

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