Renal clearance is defined as which of the following?

Renal clearance is defined as which of the following?

• A. Volume of plasma from which a substance is removed per unit time
• B. Volume of urine produced per day
• C. Amount of creatinine in urine
• D. Urine concentration of a substance divided by urine volume per unit time

Answer: (A)

Renal clearance is the rate at which the kidneys remove a substance from the blood, expressed as the volume of plasma that is completely cleared of that substance per unit time. In practical terms, it equals the excretion rate divided by the plasma concentration: clearance = (urine concentration × urine flow) / plasma concentration, with units of mL per minute. So the defining idea is the amount of plasma that is cleared of the substance each minute, not just how much urine is produced or how much of the substance is in urine alone. The daily urine volume reflects output, not clearance. The total amount excreted in urine doesn’t by itself specify how much plasma was cleared, and dividing urine concentration by urine flow ignores the plasma level, which is essential to determine how much plasma was cleared per unit time.

Renal clearance is the rate at which the kidneys remove a substance from the blood, expressed as the volume of plasma that is completely cleared of that substance per unit time. In practical terms, it equals the excretion rate divided by the plasma concentration: clearance = (urine concentration × urine flow) / plasma concentration, with units of mL per minute. So the defining idea is the amount of plasma that is cleared of the substance each minute, not just how much urine is produced or how much of the substance is in urine alone. The daily urine volume reflects output, not clearance. The total amount excreted in urine doesn’t by itself specify how much plasma was cleared, and dividing urine concentration by urine flow ignores the plasma level, which is essential to determine how much plasma was cleared per unit time.