Glomerular filtration rate (GFR) can be estimated using the renal clearance of a substance that is freely filtered and neither reabsorbed nor secreted, such as inulin: C = dfrac U times V P . If urine inulin concentration is 100 mg/dL, urine flow rate is 1.2 mL/min, and plasma inulin concentration is 1 mg/dL, what is the calculated GFR?

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MBBS QUESTION #10257

Question 1

Glomerular filtration rate (GFR) can be estimated using the renal clearance of a substance that is freely filtered and neither reabsorbed nor secreted, such as inulin: $C = \dfrac{U \times V}{P}$. If urine inulin concentration is 100 mg/dL, urine flow rate is 1.2 mL/min, and plasma inulin concentration is 1 mg/dL, what is the calculated GFR?

12 mL/min
120 mL/min✔️
1.2 mL/min
1200 mL/min

Correct Answer Explanation

$C = \dfrac{(100\ \text{mg/dL}) \times (1.2\ \text{mL/min})}{1\ \text{mg/dL}} = 120\ \text{mL/min}$, close to the normal GFR of approximately 125 mL/min — illustrating why inulin clearance is considered the gold-standard measurement of GFR.

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