Veterinary Clinical Biochemistry and Laboratory Diagnosis

INTRODUCTION

• Urea is the major end product of protein metabolism, formed in the liver via Krebs-Henseleit (urea) cycle from ammonia.
• Urea is freely filtered through the glomeruli, and 40 - 50% of urea are passively reabsorbed in proximal tubules.
• The concentration of urea is expressed as such, i.e. as urea or as the concentration of Nitrogen present in urea, i.e. blood urea nitrogen (BUN).
• Urea is found in body fluids and tissues in approximately equal concentrations. The level of urea is proportional to the dietary content of protein, i.e. to the relationship of protein catabolism and liver function.
• In healthy subjects taking an average diet, the level of urea is a highly sensitive indicator for the assessment of renal function. The increase in the level of urea usually precedes the detection of significant changes in the level of creatinine.