Renal and acid–base: glomerular haemodynamics: 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 and acid–base: glomerular haemodynamics

Sample item

In a patient with early renal artery stenosis, angiotensin II constricts the efferent arteriole more than the afferent arteriole. What happens to GFR, renal plasma flow and filtration fraction?

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

The answer and the reasoning

A. GFR maintained, plasma flow falls and filtration fraction rises

Efferent constriction raises glomerular capillary pressure, which maintains GFR, while it reduces plasma flow through the kidney. Because GFR is held while flow falls, filtration fraction rises. This is why ACE inhibitors can precipitate renal failure in bilateral renal artery stenosis.

Option by option

  • A. GFR maintained, plasma flow falls and filtration fraction rises (correct)

    Correct. Efferent constriction holds GFR up, lowers flow and raises the filtration fraction.

  • B. GFR falls, plasma flow falls and filtration fraction falls

    A fall in all three does not occur because efferent constriction preserves GFR relative to flow.

  • C. GFR rises, plasma flow rises and filtration fraction unchanged

    Efferent constriction cannot raise plasma flow; it increases resistance.

  • D. GFR falls, plasma flow rises and filtration fraction falls

    This pattern describes efferent dilation rather than constriction.

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, GFR maintained, plasma flow falls and filtration fraction rises. Efferent constriction raises glomerular capillary pressure, which maintains GFR, while it reduces plasma flow through the kidney.

Why is "GFR falls, plasma flow falls and filtration fraction falls" not the answer?

A fall in all three does not occur because efferent constriction preserves GFR relative to flow.

Why is "GFR rises, plasma flow rises and filtration fraction unchanged" not the answer?

Efferent constriction cannot raise plasma flow; it increases resistance.

Why is "GFR falls, plasma flow rises and filtration fraction falls" not the answer?

This pattern describes efferent dilation rather than constriction.

What concept does this question test?

It tests Renal and acid–base: glomerular haemodynamics in Physiology. Because GFR is held while flow falls, filtration fraction rises. This is why ACE inhibitors can precipitate renal failure in bilateral renal artery stenosis.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 and acid–base: glomerular haemodynamics?

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.