Review Note

FENA
The {{c1::fractional excretion of sodium}} (FENa) measures {{c1::the percent of filtered sodium that is excreted in the urine.}}
• This calculation is widely used to help differentiate {{c1::prerenal disease}} (decreased renal perfusion) from acute tubular necrosis (ATN) as the cause of acute kidney injury (AKI, formerly called acute renal failure).
• Compares {{c2::urinary sodium}} and {{c2::creatinine}} to {{c2::serum sodium and creatinine

FENa {{c2::< 1 %}} - seen in {{c3::pre-renal disease}}
• Kidneys are {{c4::reabsorbing Na to preserve volume}}
• OR are inappropriately {{c5::retaining sodium such as in CHF}}
• Not diagnostic {{c5::by itself}}
• GFR should also be reduced in {{c5::pre-renal disease}}

FENa {{c2::>2%}} - associated with {{c3::acute tubular necrosis (ATN)}}
FENa between {{c2::1 and 2 %}}- ??? Can be seen with {{c3::either of the above}}

This test is useless when the patient is on {{c5::diuretic therapy!!}}