Tuesday, August 17, 2010

Blood Urea Nitrogen (BUN)

1.      Blood Urea Nitrogen (BUN)




BUN correlates with uremic symptoms better than serum creatinine.


Normal Range

Adults: 7 –20mg/dL

Neonate: 5 –18 mg/dL

6 –8 mg/dL: associated with over hydration states

50 – 150mg/dL: implies serious impairment of renal function

150 –250mg/DL: is conclusive evidence of severely impaired glomerular function.



Differential diagnosis of various renal disorders; evidence of hemorrhage in Gl tract; assessment of patients requiring nutritional support in excess of catabolism (e.g. burns, cancer).

Increased in

Impaired kidney function; prerenal azotemia – ant case of reduced renal blood flow; congestive heart failure; salt and water depletion (vomiting, diarrhea, sweating); shock; postrenal azotemia – any obstruction of urinary tract (increased blood urea nitrogen [BUN] / Creatinine ratio); hemorrhage into Gl tract; AMI; stress.

Decreased in

Diuresis (e.g. with overhydration, often associated with low protein catabolism); severe liver damage (drug poisoning, hepatitis, other); increased utilization of protein for synthesis (late pregnancy, infancy, acromegaly, malnutrition ); diet (low protein and high carbohydrate, impaired absorption, malnutrition); nephritic syndrome; syndrome of inappropriate antidiuretic hormone secretion ( SIADH). 

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