Renal physiology: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Renal physiology

Sample item

Which substance is freely filtered and neither reabsorbed nor secreted, so that its clearance equals GFR?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Inulin

Inulin clearance is the reference measure of GFR. Creatinine is used in practice, but a little is secreted by the tubules so it slightly overestimates GFR. PAH clearance estimates renal plasma flow.

Option by option

  • A. Inulin (correct)

    Correct. Inulin is the textbook marker of true GFR.

  • B. Creatinine

    Creatinine is secreted slightly, so it is close to, but not exactly, GFR.

  • C. Para-aminohippuric acid

    PAH is filtered and heavily secreted, so its clearance estimates renal plasma flow.

  • D. Glucose

    Glucose is filtered but fully reabsorbed under normal conditions.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Inulin. Inulin clearance is the reference measure of GFR.

Why is "Creatinine" not the answer?

Creatinine is secreted slightly, so it is close to, but not exactly, GFR.

Why is "Para-aminohippuric acid" not the answer?

PAH is filtered and heavily secreted, so its clearance estimates renal plasma flow.

Why is "Glucose" not the answer?

Glucose is filtered but fully reabsorbed under normal conditions.

What concept does this question test?

It tests Renal physiology in Physiology. Creatinine is used in practice, but a little is secreted by the tubules so it slightly overestimates GFR. PAH clearance estimates renal plasma flow.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Renal physiology?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.