Gastroenterology: small intestinal bacterial overgrowth: 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: small intestinal bacterial overgrowth

Sample item

A 62-year-old man with known jejunal diverticulosis has chronic bloating, diarrhoea and weight loss. His haemoglobin is low with a raised mean corpuscular volume, serum vitamin B12 is low, and folate is normal to high. Which is the best non-invasive test for the likely cause?

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

The answer and the reasoning

B. Glucose or lactulose hydrogen breath test

Bacterial overgrowth in a stagnant segment deconjugates bile salts, causing fat malabsorption, and the bacteria consume vitamin B12 while synthesising folate. The hydrogen (or methane) breath test after glucose or lactulose is the usual non-invasive test, and treatment is with antibiotics such as rifaximin and correction of the cause. Jejunal aspirate culture is the invasive reference standard.

Option by option

  • A. Serum anti-tissue transglutaminase IgA

    Anti-tTG IgA screens for coeliac disease, which typically causes iron and folate deficiency instead.

  • B. Glucose or lactulose hydrogen breath test (correct)

    Early rise in breath hydrogen after a sugar load indicates fermentation by small bowel bacteria.

  • C. Faecal elastase-1 estimation

    Faecal elastase assesses exocrine pancreatic insufficiency, which does not lower B12 and raise folate.

  • D. Urea breath test

    The urea breath test detects Helicobacter pylori and not small bowel overgrowth.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is B, Glucose or lactulose hydrogen breath test. Bacterial overgrowth in a stagnant segment deconjugates bile salts, causing fat malabsorption, and the bacteria consume vitamin B12 while synthesising folate.

Why is "Serum anti-tissue transglutaminase IgA" not the answer?

Anti-tTG IgA screens for coeliac disease, which typically causes iron and folate deficiency instead.

Why is "Faecal elastase-1 estimation" not the answer?

Faecal elastase assesses exocrine pancreatic insufficiency, which does not lower B12 and raise folate.

Why is "Urea breath test" not the answer?

The urea breath test detects Helicobacter pylori and not small bowel overgrowth.

What concept does this question test?

It tests Gastroenterology: small intestinal bacterial overgrowth in General Medicine. The hydrogen (or methane) breath test after glucose or lactulose is the usual non-invasive test, and treatment is with antibiotics such as rifaximin and correction of the cause. Jejunal aspirate culture is the invasive reference standard.

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: small intestinal bacterial overgrowth?

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.