Tuesday, January 25, 2011

TOPIC DISCUSSION: Blood Urea Nitrogen ( BUN)

We associated BUN always with renal disease. What about other causes?
Why does BUN rise in GI Bleed? 
Extensive bleeding into the gastrointestinal (GI) tract will also cause an elevated BUN because digested blood is a source of urea. For example, a hemorrhage of one liter of blood into the GI tract may elevate the BUN up to 40mg/ml. Other non renal causes are: Acute myocardial infarction,Stress and excessive protein intake,steroid use or protein catabolism.

A decreased BUN may be seen in: Liver failure,Malnutrition, pregnancy, impaired nutrient absorption and SIADH
Because urea is synthesized by the liver, severe liver failure causes a reduction of urea in the blood. Just as dehydration may cause an elevated BUN, overhydration causes a decreased BUN. And finally water excess in SIADH can lead to decreased BUN.


  1. Always considered anabolic steroid use with elevated BUN:creat ratio, never a low BUN. Think of all the folks on corticosteroids.

  2. Agreed. my mistake. put it in the wrong side. Increased BUN is what we see with steroids usually.

  3. Why the elevated BUN w/ corticosteroids?

  4. Why bun decreasing when using Anabolic steroids


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