Thorax: azygos system: practice question

A Anatomy 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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Anatomy · Thorax: azygos system

Sample item

A 35-year-old man with inferior vena cava thrombosis has dilated veins that drain upward over the flanks and back. Which deep pathway provides collateral return of lower body blood to the superior vena cava?

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

The answer and the reasoning

D. Ascending lumbar veins to the azygos and hemiazygos veins

The ascending lumbar veins connect the common iliac and lumbar veins to the azygos system on the right and the hemiazygos system on the left. Blood reaches the superior vena cava through the azygos arch, bypassing an obstructed inferior vena cava. The other routes listed are portosystemic anastomoses, which matter in portal hypertension, not in caval obstruction.

Option by option

  • A. Superior rectal vein to the middle rectal veins

    This is the portosystemic anastomosis in the anal canal.

  • B. Left gastric vein to the oesophageal veins

    This is a portosystemic anastomosis relevant to portal hypertension.

  • C. Paraumbilical veins to the epigastric veins

    This is also a portosystemic route at the umbilicus, not a caval collateral.

  • D. Ascending lumbar veins to the azygos and hemiazygos veins (correct)

    Correct. The ascending lumbar veins link the lower body to the azygos system.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Ascending lumbar veins to the azygos and hemiazygos veins. The ascending lumbar veins connect the common iliac and lumbar veins to the azygos system on the right and the hemiazygos system on the left.

Why is "Superior rectal vein to the middle rectal veins" not the answer?

This is the portosystemic anastomosis in the anal canal.

Why is "Left gastric vein to the oesophageal veins" not the answer?

This is a portosystemic anastomosis relevant to portal hypertension.

Why is "Paraumbilical veins to the epigastric veins" not the answer?

This is also a portosystemic route at the umbilicus, not a caval collateral.

What concept does this question test?

It tests Thorax: azygos system in Anatomy. Blood reaches the superior vena cava through the azygos arch, bypassing an obstructed inferior vena cava. The other routes listed are portosystemic anastomoses, which matter in portal hypertension, not in caval obstruction.

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 Thorax: azygos system?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.