Final answer:
The test to determine the level of nitrogenous waste in the body measures non-protein nitrogenous substances, primarily urea, in the blood, which can indicate kidney function.
Step-by-step explanation:
The test performed to determine nitrogenous waste in the body is the estimation of non-protein nitrogenous substances (NPN), which predominantly includes urea, uric acid, and creatinine. In the context of kidney function evaluation, the concentration of these substances in the blood provides crucial information about renal health. Normally, blood urea is maintained at a concentration of 15-40 mg/100 ml. When the kidneys are not functioning properly, there will be an increase in the levels of NPN, with significant rises seen in cases of total renal failure.
Additionally, there are various methods to estimate blood urea, including the Diacetyl Monooxime (DAM) method, colorimetric methods using the urease enzyme, and autoanalyzer methods. Urea itself is synthesized in the liver from ammonia released by the oxidation of amino acids and is then excreted in the urine.