Urea

The main byproduct of protein nitrogen metabolism is urea. It is created in the liver via the urea cycle from ammonia, which is created by the deamination of amino acids. The majority of urea excretion comes from the kidneys, but small amounts are also expelled through perspiration and broken down by bacteria in the intestines. The most used test for screening renal function is blood urea nitrogen determination. It can help with the differential diagnosis of prerenal, renal, and postrenal azotemia when combined with serum creatinine measurements. Blood urea nitrogen concentrations are elevated in renal-related conditions such as tubular necrosis, glomerular-nephritis (renal causes), shock, reduced blood volume, chronic nephritis, nephrosclerosis, and urinary tract blockage (postrenal causes). Additionally, transient spikes may be observed during times when protein intake is substantial. Liver illnesses are characterised by unpredictable levels.