Using the Cockcroft-Gault equation, estimate CrCl for a 65-year-old man weighing 72 kg with serum creatinine 1.8 mg/dL.

• A. 38 mL/min
• B. 42 mL/min
• C. 46 mL/min
• D. 50 mL/min

Answer: (B)

The question tests how to estimate creatinine clearance with the Cockcroft-Gault equation, which uses age, weight, and serum creatinine, applying a sex correction only for females. For a man, the formula is CrCl ≈ [(140 − age) × weight] / (72 × serum creatinine). Plugging in the numbers: (140 − 65) = 75; 75 × 72 kg = 5400; 72 × 1.8 = 129.6. Dividing 5400 by 129.6 gives about 41.7 mL/min. This rounds to roughly 42 mL/min, matching the best estimate among the options. Remember, if the patient were female, you’d multiply the result by 0.85, and in cases of obesity or very abnormal body composition you might choose a different weight (e.g., adjusted or ideal body weight) for more accuracy.