Amount of urea in blood
¼ODof testamount of standard mgðÞ 100 dilution factor
ODof standardvolume of sample mlðÞ 1000¼xg=dlAmount of urea in urine
¼OD of testamount of standardðmgÞ 1000 dilution factor
OD of standardvolume of sampleðmlÞ 1000¼xg=L16.7 Clinical Significance...............................
The normal range of blood urea is 15–40 mg/dl, and urinary excretion is 15–40 g/
day. Increase in blood urea is called uremia, and it occurs in wide variety of diseases.
Uremia is of three types:
Prerenal UremiaIt is caused by mild dehydration, high protein catabolism, muscle
wasting as in starvation, reabsorption of blood protein after a gastrointestinal
hemorrhage, treatment with cortisol, and decreased perfusion of kidneys.
Renal Uremia The blood urea is increased in all forms of kidney diseases. In acute
glomerulonephritis values goes up to 300%.
Postrenal Uremia It is caused by conditions such as nephrolithiasis, enlargement
of prostate gland, tumors of the urinary bladder, and stones in ureters. These
conditions obstruct the urine outflow through ureters, bladder, or urethra.
Decrease in blood urea is rare. It has been reported in some cases of severe
diseases, e.g., viral hepatitis with extensive necrosis. Levels also decrease in low
protein diet intake. In pregnancy, blood urea level is lower (15–20 mg/dl).
70 16 Estimation of Urea in Serum and Urine