Urea

Also known as:	Blood Urea Nitrogen - BUN
See also:	Urea in lizards

Description

Urea is a form of nitrogenous waste formed from ammonia via the urea cycle in the liver. It freely crosses lipid membranes and is filtered into the glomerular filtrate in the renal glomerulus. A proportion of this filtered urea is reabsorbed passively before final excretion and it forms a vital of the concentration gradient needed to prevent passive diuresis.

Clinical Significance

An increase in serum concentrations of urea and creatinine is known as azotaemia and it is found almost exclusively in animals with kidney disease.

Blood urea coentration may be elevated independently of creatinine for the following reasons:

• Gastro-intestinal haemorrhage, as with gastro-duodenal ulceration.
• Diet with high purine content, such as liver.

Reduced urea concentration: