Which statement about creatinine and kidney function testing is supported by the material?

Which statement about creatinine and kidney function testing is supported by the material?

• A. Creatinine clearance directly measures urine urea clearance
• B. Creatinine clearance is routinely used to assess the glomerular filtration rate
• C. Creatinine is not excreted in urine
• D. Creatinine is only produced in the liver

Answer: (B)

Creatinine clearance is used to estimate glomerular filtration rate because creatinine is produced at a nearly constant rate by muscle and is cleared by the kidneys primarily by filtration, with only a small amount secreted by the tubules. This makes its clearance a good practical proxy for how well the kidneys are filtering blood. In the test, the standard approach is to measure creatinine in a timed urine collection and in a blood sample, then calculate clearance as (urine creatinine concentration × urine volume) / plasma creatinine concentration. Although not perfect—tubular secretion and variations in muscle mass, age, and sex can affect the value—it remains a routine way to assess GFR. The other statements don’t fit: creatinine is indeed excreted in urine; it is produced in muscle, not the liver; and creatinine clearance does not measure urine urea clearance.

Creatinine clearance is used to estimate glomerular filtration rate because creatinine is produced at a nearly constant rate by muscle and is cleared by the kidneys primarily by filtration, with only a small amount secreted by the tubules. This makes its clearance a good practical proxy for how well the kidneys are filtering blood. In the test, the standard approach is to measure creatinine in a timed urine collection and in a blood sample, then calculate clearance as (urine creatinine concentration × urine volume) / plasma creatinine concentration. Although not perfect—tubular secretion and variations in muscle mass, age, and sex can affect the value—it remains a routine way to assess GFR.

The other statements don’t fit: creatinine is indeed excreted in urine; it is produced in muscle, not the liver; and creatinine clearance does not measure urine urea clearance.