Calculate creatinine clearance, given the following information: serum creatinine 1.2 mg/dL; urine creatinine 120 mg/dL; urine volume 1750 mL/24 h; body surface area 1.80 m2.

Calculate creatinine clearance, given the following information: serum creatinine 1.2 mg/dL; urine creatinine 120 mg/dL; urine volume 1750 mL/24 h; body surface area 1.80 m2.

• A. 112 mL/min/1.73 m^2
• B. 117 mL/min/1.73 m^2
• C. 125 mL/min/1.73 m^2
• D. 130 mL/min/1.73 m^2

Answer: (B)

Creatinine clearance estimates how much plasma is cleared of creatinine each minute, serving as a practical proxy for glomerular filtration rate. It uses the ratio of creatinine excreted in urine to creatinine remaining in blood, scaled by how much urine is produced per minute and then normalized to body surface area. First convert the urine volume to a per-minute rate: 1750 mL over 24 hours equals 1750 / 1440 ≈ 1.215 mL/min. Next, use the clearance formula CrCl = (U_cr × V) / P_cr, where U_cr is urine creatinine (mg/dL), V is urine flow (mL/min), and P_cr is plasma creatinine (mg/dL). The ratio U_cr / P_cr = 120 / 1.2 = 100. So CrCl ≈ 100 × 1.215 ≈ 121.5 mL/min. Finally, normalize to a standard body surface area of 1.73 m^2: CrCl_norm = CrCl × (1.73 / BSA) = 121.5 × (1.73 / 1.80) ≈ 121.5 × 0.961 ≈ 117 mL/min/1.73 m^2. So the result is about 117 mL/min/1.73 m^2, matching the given option.

Creatinine clearance estimates how much plasma is cleared of creatinine each minute, serving as a practical proxy for glomerular filtration rate. It uses the ratio of creatinine excreted in urine to creatinine remaining in blood, scaled by how much urine is produced per minute and then normalized to body surface area.

First convert the urine volume to a per-minute rate: 1750 mL over 24 hours equals 1750 / 1440 ≈ 1.215 mL/min.

Next, use the clearance formula CrCl = (U_cr × V) / P_cr, where U_cr is urine creatinine (mg/dL), V is urine flow (mL/min), and P_cr is plasma creatinine (mg/dL). The ratio U_cr / P_cr = 120 / 1.2 = 100. So CrCl ≈ 100 × 1.215 ≈ 121.5 mL/min.

Finally, normalize to a standard body surface area of 1.73 m^2: CrCl_norm = CrCl × (1.73 / BSA) = 121.5 × (1.73 / 1.80) ≈ 121.5 × 0.961 ≈ 117 mL/min/1.73 m^2.

So the result is about 117 mL/min/1.73 m^2, matching the given option.