Ammonia is metabolized by the liver and eliminated by the kidneys. Levels of which metabolic byproduct of ammonia are measured to assess kidney function?

Ammonia is metabolized by the liver and eliminated by the kidneys. Levels of which metabolic byproduct of ammonia are measured to assess kidney function?

• A. Phosphorus
• B. Urea nitrogen
• C. Creatinine
• D. Aspartate aminotransferase

Answer: (B)

Ammonia is detoxified in the liver by converting it into urea, which is then carried in the blood to the kidneys for excretion. Measuring the level of urea nitrogen in the blood (BUN) reflects how well the kidneys are filtering waste; if kidney function is impaired, urea builds up and BUN rises. Creatinine is also used to assess kidney function, but it comes from muscle metabolism, not ammonia, so it’s a different marker. Phosphorus is a mineral, and AST is a liver enzyme, neither of which directly represent the ammonia waste product.

Ammonia is detoxified in the liver by converting it into urea, which is then carried in the blood to the kidneys for excretion. Measuring the level of urea nitrogen in the blood (BUN) reflects how well the kidneys are filtering waste; if kidney function is impaired, urea builds up and BUN rises. Creatinine is also used to assess kidney function, but it comes from muscle metabolism, not ammonia, so it’s a different marker. Phosphorus is a mineral, and AST is a liver enzyme, neither of which directly represent the ammonia waste product.