Fractional_urea_excretion v.1
Fractional excretion of urea (FEUrea) is the percentage of blood urea nitrogen filtered by the kidney which is excreted in the urine. FEUrea helps distinguish between prerenal and intrinsic renal causes of acute renal failure, specifically prerenal azotemia and acute tubular nerosis (ATN). Though less common than fractional excretion of sodium (FENa), it is more specific and sensitive and potentially more useful because urea excretion (unlike sodium) is not significantly affected by diuretics. The calculation requires blood urea nitrogen (BUN) and urine urea (uUrea) concentrations (mmol/L or mg/dl), and serum (sCr) and urine (uCr) creatinine concentrations (umol/L or mg/dl). FEUrea <= 35% suggests kidney injury of prerenal etiology while FEUrea > 50% suggests an intrinsic renal etiology.
To determine the proportion of urea excreted in the urine compared with the total amount of urea filtered by the kidneys, and help differentiate between pre-renal and intrinsic renal causes of renal failure and acute kidney injury.
To calculate FEUrea (%) from given values of urea (mmol/L or mg/dl) and creatinine (umol/L or mg/dl) detected in serum and urine samples. To determine if acute renal failure/kidney injury is due to prerenal (FEUrea <= 35%) or intrinsic renal (FEUrea > 50%) etiology. Etiology of acute kidney injury (AKI) should be based upon the totality of the presentation (history, clinical examination, urine microscopy, and, when appropriate, response to volume resuscitation), not just on the FEUrea.
FEUrea is a useful discriminator in acute renal failure, not chronic renal failure.
Carvounis CP, Nisar S, Guro-Razuman S. Significance of the fractional excretion of urea in the differential diagnosis of acute renal failure. Kidney international. 2002 Dec 31;62(6):2223-9.
OBSERVATION.lab_test-fractional_urea_excretion.v1, EVALUATION.fractional_urea_excretion.v1
