Final answer:
The correct equation for determining clearance is Clearance = excretion rate/plasma concentration. This applies when measuring how efficiently the kidneys remove a substance like creatinine or inulin from the blood. Creatinine clearance is a common test for this purpose and is adjusted for body surface area (BSA).
Step-by-step explanation:
Correct Equation for Determining Clearance
The correct equation for determining clearance is:
Clearance = excretion rate/plasma concentration
This equation is applicable when evaluating the clearance of a substance such as creatinine or inulin from the blood by the kidneys. Clearance can be thought of as the volume of plasma from which the substance has been completely removed per unit time. Therefore, it is incorrect to multiply or divide the filtered load by the glomerular filtration rate (GFR). Instead, clearance is a measure of the rate at which a substance is eliminated from the body, and it is calculated by dividing the excretion rate of the substance in the urine by its plasma concentration.
The creatinine clearance test is a standard method to estimate the GFR. The clearance of creatinine (Ccr) is calculated using the formula:
Ccr = (U x V)/B
where U is the concentration of creatinine in urine, V is the urine flow rate, and B is the plasma concentration of creatinine. To account for individual body size, creatinine clearance is often corrected for the body surface area (BSA).