You should use the same unit for plasma urea and urinary urea, and the same unit for plasma and urinary creatinine.
The Fractional Excretion of Urea is an indicator of renal function. It indicates the part of urea filtered by the glomeruli which is effectively eliminated.
Use in the differential diagnosis of acute renal failure, particularly after the use of diuretics as reduces the usability of the excreted fraction of sodium.
Formula: Fractional Excretion of Urea = (urinary urea x plasma creatinine)/ (plasma urea x urinary creatinine).
Urea is a protein breakdown product that is eliminated through urine. Blood urea levels are therefore a reflection of kidney function and, under certain conditions, dietary protein intake and liver function. However, blood creatinine and estimated glomerular filtration rate measurements are generally used rather than urea measurements to assess kidney function.
A high level of urea in the blood usually suggests poor functioning of the kidneys, acute or chronic. High urea levels can also be attributed to a condition that reduces blood flow to the kidneys. More rarely, urea levels may reveal accelerated catabolism (intracellular digestion) of proteins, a significant increase in dietary protein intake, or digestive bleeding (reabsorption of protein from the blood in the gut). Certain medications can also cause an increase in urea levels.
Low urea levels are usually of little clinical significance. They may, however, reflect severe liver disease, malnutrition, or too much water in the blood.