Abdomen and pelvis: horseshoe ischiorectal abscess: 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 · Abdomen and pelvis: horseshoe ischiorectal abscess

Sample item

A man has a large abscess in the right ischiorectal fossa. Two weeks later a similar abscess forms in the left fossa although no skin has been breached across the midline. Through which route has the infection spread?

AAlong the pudendal canal to the ischial spineBBehind the anal canal through the deep postanal spaceCIn front of the anal canal over the perineal bodyDThrough the obturator canal into the thigh

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

The answer and the reasoning

B. Behind the anal canal through the deep postanal space

The two ischiorectal fossae communicate behind the anal canal through the deep postanal space, below the levator ani and above the anococcygeal ligament. Infection spreads this way to form a horseshoe abscess. In front, the perineal body and the transverse perineal muscles prevent such communication.

Option by option

A. Along the pudendal canal to the ischial spine
The pudendal canal lies in the lateral wall of one fossa and does not cross to the other side.
B. Behind the anal canal through the deep postanal space (correct)
Correct. The fossae communicate behind the anal canal by the deep postanal space.
C. In front of the anal canal over the perineal body
The fossae do not communicate anteriorly because the perineal body and transverse perineal muscles block the way.
D. Through the obturator canal into the thigh
The obturator canal leads to the medial thigh and does not connect the fossae.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Behind the anal canal through the deep postanal space. The two ischiorectal fossae communicate behind the anal canal through the deep postanal space, below the levator ani and above the anococcygeal ligament.

Why is "Along the pudendal canal to the ischial spine" not the answer?

The pudendal canal lies in the lateral wall of one fossa and does not cross to the other side.

Why is "In front of the anal canal over the perineal body" not the answer?

The fossae do not communicate anteriorly because the perineal body and transverse perineal muscles block the way.

Why is "Through the obturator canal into the thigh" not the answer?

The obturator canal leads to the medial thigh and does not connect the fossae.

What concept does this question test?

It tests Abdomen and pelvis: horseshoe ischiorectal abscess in Anatomy. Infection spreads this way to form a horseshoe abscess. In front, the perineal body and the transverse perineal muscles prevent such communication.

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 Abdomen and pelvis: horseshoe ischiorectal abscess?

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.