In the creatinine clearance calculation example, the urine creatinine concentration was which value?

• A. 60 mg/dL
• B. 120 mg/dL
• C. 240 mg/dL
• D. 480 mg/dL

Answer: (B)

The key idea is that creatinine clearance estimates GFR by comparing how much creatinine is in urine to how much is in the blood, scaled by how much urine is produced. The formula is Ccr = (Ucr × V) / Pcr, with Ucr being the urine creatinine concentration, V the urine flow rate (volume per time), and Pcr the plasma creatinine concentration. In the example, the urine creatinine concentration used is 120 mg/dL, which falls in the typical range for these problems and aligns with the given V and P to yield the stated clearance. Values like 60 mg/dL would lower the clearance because the numerator would be smaller, while 240 or 480 mg/dL would push the clearance higher, so they aren’t the value used in that calculation.