Thorax: costodiaphragmatic recess: 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: costodiaphragmatic recess

Sample item

A 45-year-old man with early pleural effusion has blunting of the costophrenic angle on a standing chest radiograph. Why is fluid seen first in this location?

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

The answer and the reasoning

D. The costodiaphragmatic recess is the lowest part of the pleural cavity and is not filled by lung in quiet breathing

The costodiaphragmatic recess is the dependent slit between costal and diaphragmatic pleura that the lung enters only in deep inspiration. Fluid collects there by gravity and typically needs about 200 to 300 mL to blunt the angle on a standing film. Thoracocentesis is done above the upper border of a lower rib in the posterior axillary or scapular line.

Option by option

  • A. The cardiophrenic recess has no pleural lining

    The cardiophrenic region is also lined by pleura; the lining is not absent.

  • B. The pulmonary ligament directs fluid towards the costal margin

    The pulmonary ligament is a pleural fold below the lung root and does not direct fluid.

  • C. The lung root is fixed and prevents fluid from collecting elsewhere

    The lung root being fixed does not determine the site of dependent fluid collection.

  • D. The costodiaphragmatic recess is the lowest part of the pleural cavity and is not filled by lung in quiet breathing (correct)

    Correct. Gravity pools fluid in the lowest part of the pleural sac, the costodiaphragmatic recess.

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, The costodiaphragmatic recess is the lowest part of the pleural cavity and is not filled by lung in quiet breathing. The costodiaphragmatic recess is the dependent slit between costal and diaphragmatic pleura that the lung enters only in deep inspiration.

Why is "The cardiophrenic recess has no pleural lining" not the answer?

The cardiophrenic region is also lined by pleura; the lining is not absent.

Why is "The pulmonary ligament directs fluid towards the costal margin" not the answer?

The pulmonary ligament is a pleural fold below the lung root and does not direct fluid.

Why is "The lung root is fixed and prevents fluid from collecting elsewhere" not the answer?

The lung root being fixed does not determine the site of dependent fluid collection.

What concept does this question test?

It tests Thorax: costodiaphragmatic recess in Anatomy. Fluid collects there by gravity and typically needs about 200 to 300 mL to blunt the angle on a standing film. Thoracocentesis is done above the upper border of a lower rib in the posterior axillary or scapular line.

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: costodiaphragmatic recess?

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.