1. Urea
Clinical significance
1) Physiologic changes in urea concentration
The concentration of urea depends on diet. The individuals taking food with high protein
content have a higher serum urea concentration than those taking food with low protein
content. Urea is normally lower in children and women because of their lower muscular
mass than in men.
A) Increased levels
• in healthy individuals, the blood urea concentration increases with dietary protein,
• the concentration of urea increases with age,
• in late pregnancy because of increased protein intake.
B) Decreased levels
• blood urea concentration is lower in children during growth than in adults,
• in early normal pregnancy,
• in individuals on a low-protein high-carbohydrate diet
2) Pathologic changes in urea concentration
A) Increased urea levels in:
• Excessive urea production
- intake of high-protein diet 12 hours before blood sampling,
- enhanced catabolism of body protein.
• Incomplete urea clearance from the body
- renal failure,
- postrenal failure,
- prerenal failure,
• acquired hemolytic anemia (autoimmune) ,
• acute pancreatitis,
• acute poststreptococcal glomerulonephritis,
• acute renal failure,
• atherosclerosis,
• benign prostatic hypertrophy,
• bladder carcinoma,
• cholera,
• chronic lymphocytic leukemia,
• chronic pyelonephritis,
• chronic renal failure,
• congestive heart failure ,
• cystinosis
• diabetes mellitus,
• glomerulonephritis,
• glomerulonephritis, membranoproliferative,
• Goodpasture’s syndrome,
• gout,
• heavy chain disease (gamma),

2. • hepatic failure,
• hydronephrosis
• hyperthyroidism,
• IgA nephropathy,
• intestinal obstruction,
• lead poisoning,
• leptospirosis,
• liver cirrhosis,
• medullary cystic disease,
• multiple myeloma,
• nephrotic syndrome,
• non-Hodgkins lymphoma,
• polycystic kidney disease,
• pre-eclampsia,
• septicemia,
• shock,
• SLE,
• urethritis.
• vomiting,
B) Decreased urea levels in:
• acromegaly,
• acute and subacute necrosis of the liver,
• after glucose infusion,
• after hemodialysis,
• celiac disease,
• cystic fibrosis,
• eclampsia,
• hepatic failure.
• hepatolenticular degeneration,
• Laennec’s or alcoholic cirrhosis,
• liver cirrhosis,
• liver disease,
• nephrotic syndrome,
• pre-eclampsia,
• protein malnutrition,
• toxic hepatitis,
There were significant negative relationships between the blood urea nitrogen (BUN) level and the birth
weight or gestational age in the latter cohort. A birth weight equal to or greater than 1500 g or a
gestational age equal to or exceeding 32 weeks corresponded to BUN levels of 48-49 mg/dl or less.
Whether the low BUN is the direct cause of the improved outcome remains to be examined.

3. Renal function and urea are frequently abnormal in patients with heart failure (HF) and are predictive of
increased mortality. The relative importance of each parameter is less clear. We prospectively compared
the predictive value of renal function and serum urea on clinical outcome in patients with HF.