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−{{unfinished}}+
−{| cellpadding="10" cellspacing="0" border="1"
−| Also known as:
−|'''Blood Urea Nitrogen - BUN'''
−|-
−| See also:
−|'''[[Blood urea nitrgoen|Urea in lizards]]'''
−|}
Also known as '''''Blood Urea Nitrogen — BUN
−==Description==
==Description==
Urea is a form of nitrogenous waste formed from [[Ammonia|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.
Urea is a form of nitrogenous waste formed from [[Ammonia|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==
==Clinical Significance==
An increase in serum concentrations of urea and creatinine is known as '''[[Azotaemia|azotaemia]]''' and it is found almost exclusively in animals with kidney disease.
An increase in serum concentrations of urea and creatinine is known as '''[[Azotaemia|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:
Blood urea coentration may be elevated independently of creatinine for the following reasons:
−*Gastro-intestinal haemorrhage, as with [[Gastric Ulcer - Dog|gastro-duodenal ulceration]].
+*Gastro-intestinal haemorrhage, as with [[Gastric Ulceration - Dog|gastro-duodenal ulceration]].
−*Diet with high purine content, such as liver.
+*Diet with high protein or purine content, such as liver.
+*Increased catabolism of body tissues, particularly muscle, which may occur in pyrexic animals or those with systemic disease.
−Reduced urea concentration:
+Reduced urea concentration may occur due to:
+*Over-enthusiastic fluid therapy, diluting the urea present in the blood.
+*Disease that cause polyuria and/or polydipsia may cause 'medullary washout' of urea. Common examples include pyschogenic polydipsia, [[Diabetes Insipidus|diabetes insipidus]] and [[Hyperadrenocorticism|Cushing's disease]].
+*Reduced synthesis with [[Portosystemic Shunt|porto-systemic shunts]], [[Hepatic Microvascular Dysplasia|microvascular dysplasia]] or liver failure.
+*A diet with a low protein content or malnutrition.
−[[Category:Blood_Sample]][[Category:Dog]][[Category:Cat]][[Category:Cattle]][[Category:Sheep]][[Category:Horse]][[Category:Pig]][[Category:Donkey]][[Category:To_Do_-_James]]
+{{unfinished}}
+[[Category:Blood Biochemistry Changes]][[Category:To_Do_-_Blood]]