Chemistry evaluation of the kidney includes measurement of metabolic wastes in the blood in the form of:

• A. AST/ALT
• B. Ammonia and pyruvic acid
• C. Bilirubin and urobilinogen
• D. Urea nitrogen and creatinine

Answer: (A)

The key idea is that kidney function is assessed by how well the blood is cleared of waste products produced by metabolism. The most informative blood markers for this are urea nitrogen and creatinine. Urea nitrogen comes from protein breakdown in the liver and is filtered by the kidneys; creatinine is a waste product of muscle metabolism that is normally filtered and excreted by the kidneys. Together, they reflect the kidneys’ ability to filter and excrete waste.

Options involving AST/ALT are liver enzymes used to gauge liver injury, not kidney function. Ammonia and pyruvic acid are metabolic byproducts but are not standard indicators of renal filtration. Bilirubin and urobilinogen relate to the liver and biliary system and red blood cell turnover, not to kidney waste removal. Therefore, measuring urea nitrogen and creatinine best represents the kidney’s ability to clear metabolic wastes from the blood.