BLOOD UREA NITROGEN
Blood urea nitrogen is formed entirely by liver deamination from protein metabolism.
BUN is a byproduct due to the release of nitrogen bonds (and measures the nitrogen portion of urea) from protein substances in the liver.
From a pathological perspective, an increased blood urea nitrogen would indicate renal disease, tissue necrosis, increased adrenal gland activity, and rapid protein catabolism.
From a physiologic perspective, the purpose of nitrogen is to carry a substance through an aerobic media preventing oxidation, and eventually back into an anaerobic environment. Once in the liver the thyroid through the use of iodine, releases the nitrogen bond, releasing the nitrogen from the protein, allowing the protein to combust into hormones, enzymes and antibodies.
The adrenals and anterior pituitary play a vital role in the combustion of this protein. The urea is now sent to the kidneys and is converted into urine.
Urea is produced when amino acids, which are not used for protein synthesis, are broken down via hepatic metabolism. These amino acids are de-aminated producing ammonia, which is converted to urea immediately since ammonia levels become toxic. When this metabolic conversion is affected due to faulty metabolism or liver disease ammonia is not converted causing excessive levels of ammonia with possible hepatic encephalopathy.
Renal malfunction/failure may also cause a high BUN due to its affect on the removal of urea causing uremia. Uremic wastes usually impair platelet function, and patients may show an increased tendency towards bleeding.
BUN IS HIGH WHEN
General considerations:
¬ High protein diets can cause increased BUN
¬ Increase water intake if no edema
