BUN

The principal waste product of protein catabolism is urea. Urea is synthesized in the liver as the end product of protein metabolism and amino acid degradation. Urea is then transported to the kidneys by the blood where it is readily filtered and passed out in the urine. The importance of urea nitrogen determination is its value as an indicator of liver and kidney functions. This test measures the ratio between urea production and urea clearance. Increases in blood urea nitrogen (BUN) are found in congestive heart failure, shock, hemorrhage, Addison’s disease, acute and chronic renal failure, glomerular nephritis and urinary tract obstruction. Decreases in blood urea nitrogen (BUN) are seen with decreased protein intake, severe liver disease and normal pregnancy.