Abdominal and GI imaging: renal infarct cortical rim sign: practice question

A Radiology 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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Radiology · Abdominal and GI imaging: renal infarct cortical rim sign

Sample item

A patient with atrial fibrillation has sudden flank pain, haematuria and raised LDH. Contrast CT shows a wedge-shaped non-enhancing area of kidney with a thin rim of enhancing outer cortex. Why is the outer cortex preserved?

ACollateral supply from capsular arteriesBSupply from the vasa recta of the medullaCContrast pooling in the collecting systemDVenous drainage through the renal vein

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

The answer and the reasoning

A. Collateral supply from capsular arteries

In renal artery branch occlusion the infarcted parenchyma does not enhance, but the thin outer rim of cortex survives because it is fed by capsular and perforating collateral vessels. This is the cortical rim sign and supports infarction over tumour or pyelonephritis. It may be absent in acute cases.

Option by option

A. Collateral supply from capsular arteries (correct)
Correct. Capsular collateral arteries keep the outer cortex perfused.
B. Supply from the vasa recta of the medulla
The vasa recta supply the medulla, not the outer cortex.
C. Contrast pooling in the collecting system
Collecting-system contrast appears only in a later excretory phase and is central.
D. Venous drainage through the renal vein
Venous drainage does not supply oxygen or contrast to tissue.

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.

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is A, Collateral supply from capsular arteries. In renal artery branch occlusion the infarcted parenchyma does not enhance, but the thin outer rim of cortex survives because it is fed by capsular and perforating collateral vessels.

Why is "Supply from the vasa recta of the medulla" not the answer?

The vasa recta supply the medulla, not the outer cortex.

Why is "Contrast pooling in the collecting system" not the answer?

Collecting-system contrast appears only in a later excretory phase and is central.

Why is "Venous drainage through the renal vein" not the answer?

Venous drainage does not supply oxygen or contrast to tissue.

What concept does this question test?

It tests Abdominal and GI imaging: renal infarct cortical rim sign in Radiology. This is the cortical rim sign and supports infarction over tumour or pyelonephritis. It may be absent in acute cases.

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 Abdominal and GI imaging: renal infarct cortical rim sign?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.