Blood urea nitrogen (BUN) Blood urea nitrogen (BUN)

Elevation of blood urea nitrogen (BUN) concentrations may be caused by many different things including pre-renal and post-renal factors and should not be considered diagnostic of primary renal disease in all cases. Addiblood biochemistry and urinalysis are necessary to evaluate fully the cause of high BUN concentrations. To eliminate dietary factors BUN should be performed on blood collected after 12 hours starvation.

Cat Normal Range: 5-11 mmol/l
Dog Normal range: 2.5-7 mmol/l

In old animals undergoing routine screening a high BUN may indicate the presence of:

Pre-renal causes



Cats are obligate carnivores and have liver enzyme systems for protein metabolism which do not down-regulate in the presence of reduced prointake in the diet. As a consequence of this, and of the large number of clinical conditions that can lead to catabolism, a high BUN, muscle wastage and weight loss are common features in old cats. In fact, almost any major organ system disorder is accompanied by severe catabolism and loss of lean body mass in the cat.

Low BUN concentrations are seen in animals on low protein rations or in the presence of liver failure or acquired portosystemic shunts.