Creatinine clearance results are corrected using a patient's body surface area to account for differences in which factor?

• A. Muscle mass
• B. Age
• C. Dietary intake
• D. Sex

Answer: (A)

The important idea is that creatinine clearance is adjusted for body surface area because creatinine production depends on muscle mass. People with more muscle produce more creatinine, so their raw clearance values can appear higher simply due to larger body size and greater lean mass, not because their kidneys are filtering more efficiently. By normalizing to a standard body surface area (1.73 m^2), we remove the influence of overall body size and lean body mass, allowing fairer comparisons of renal function across individuals. Dietary intake and age or sex can influence creatinine levels in other ways, but the body surface area correction specifically targets differences in muscle mass/body size.