Fractionated Excretion of Sodium

Fractionated Excretion of Sodium

Alternate Test Name

FENA

Epic Mnemonic
Sunquest Mnemonic

LAB3153
FENA

Category

Chemistry

Methodology

Calculation

Test Performance Schedule

Sunday - Saturday

Result Availability

Within 24 hours – STAT upon request

Container

Gold top (SST) or Green top (lithium heparin) tube
and Urine tube without preservative

Volume

Pref. Vol.: 1.0 mL serum, 1.0 mL urine
Min. Vol.: 0.5 mL serum, 0.5 mL urine

Collection Instructions

• Collect Plasma or Serum concurrently with Random Urine

Transportation Instructions

Refrigerated or on ice

Stability

• Refrigerated: 5 days

CPT Codes

n/a

Effective/Revised

2/25/2019

Urine sodium excretions are helpful when the urine output is low (<500 mL/24 hr). However, a more accurate test to determine the cause of reduced urine output is the fractional excretion of sodium (FE_na). This is the fraction of sodium actually excreted relative to the amount filtered by the kidney. FENA is a calculation based on the concentrations of sodium and creatinine in the plasma (or serum) and the urine.

A low FENA (<1%) is associated with conditions like Prerenal Azotemia, Acute Glomerular Nephritis and Hepatorenal Syndrome. A high FENA (>2%) is associated with Acute Tubular Necrosis, Uirinary Obstruction, Chronic Uremia and Diuretics.