Gastroenterology: bile acid diarrhoea after ileal resection: practice question

A General Medicine 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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General Medicine · Gastroenterology: bile acid diarrhoea after ileal resection

Sample item

A 40-year-old man had 60 cm of terminal ileum resected for Crohn disease. Six months later he has watery, non-bloody diarrhoea, and stool fat excretion is normal. What is the most likely mechanism of the diarrhoea?

ABile salt depletion causing fat malabsorption and steatorrhoeaBLactase deficiency caused by loss of the brush borderCPancreatic exocrine insufficiency from loss of ileal feedbackDUnabsorbed bile salts stimulating colonic water and electrolyte secretion

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

The answer and the reasoning

D. Unabsorbed bile salts stimulating colonic water and electrolyte secretion

Conjugated bile salts are reabsorbed in the terminal ileum. After a limited resection (below about 100 cm), more bile salts reach the colon and cause secretory (cholerrheic) diarrhoea that responds to cholestyramine. After longer resections the bile salt pool is depleted and steatorrhoea results. Vitamin B12 absorption is also lost.

Option by option

A. Bile salt depletion causing fat malabsorption and steatorrhoea
Steatorrhoea occurs with larger resections that exhaust the bile salt pool, and here the stool fat is normal.
B. Lactase deficiency caused by loss of the brush border
Lactase is present throughout the small bowel and limited ileal resection does not cause lactose intolerance.
C. Pancreatic exocrine insufficiency from loss of ileal feedback
Pancreatic secretion is not controlled by ileal bile salt feedback, and stool fat would be raised.
D. Unabsorbed bile salts stimulating colonic water and electrolyte secretion (correct)
Correct. Bile salts in the colon inhibit water absorption and stimulate secretion.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Unabsorbed bile salts stimulating colonic water and electrolyte secretion. Conjugated bile salts are reabsorbed in the terminal ileum.

Why is "Bile salt depletion causing fat malabsorption and steatorrhoea" not the answer?

Steatorrhoea occurs with larger resections that exhaust the bile salt pool, and here the stool fat is normal.

Why is "Lactase deficiency caused by loss of the brush border" not the answer?

Lactase is present throughout the small bowel and limited ileal resection does not cause lactose intolerance.

Why is "Pancreatic exocrine insufficiency from loss of ileal feedback" not the answer?

Pancreatic secretion is not controlled by ileal bile salt feedback, and stool fat would be raised.

What concept does this question test?

It tests Gastroenterology: bile acid diarrhoea after ileal resection in General Medicine. After a limited resection (below about 100 cm), more bile salts reach the colon and cause secretory (cholerrheic) diarrhoea that responds to cholestyramine. After longer resections the bile salt pool is depleted and steatorrhoea results. Vitamin B12 absorption is also lost.

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 Gastroenterology: bile acid diarrhoea after ileal resection?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.