Hepatobiliary: brown pigment stones: practice question

A Pathology 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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Pathology · Hepatobiliary: brown pigment stones

Sample item

A 62-year-old man has recurrent episodes of fever, jaundice and right upper quadrant pain. ERCP shows soft, greasy brown stones in dilated bile ducts with a stricture. What is the main mechanism of stone formation?

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

The answer and the reasoning

C. Bacterial beta-glucuronidase deconjugating bilirubin in infected, stagnant bile

Brown pigment stones form in the bile ducts when bile stasis and infection with enteric bacteria such as Escherichia coli lead to deconjugation of bilirubin glucuronides by bacterial beta-glucuronidase. The insoluble unconjugated bilirubin precipitates with calcium. Parasites such as Ascaris or liver flukes may be associated.

Option by option

  • A. Supersaturation of bile with cholesterol from raised HMG-CoA reductase

    Cholesterol supersaturation produces gallbladder cholesterol stones in obese women.

  • B. Intravascular haemolysis increasing unconjugated bilirubin load

    Chronic haemolysis causes black pigment stones in the gallbladder.

  • C. Bacterial beta-glucuronidase deconjugating bilirubin in infected, stagnant bile (correct)

    Correct. Infection and stasis allow bacterial deconjugation of bilirubin.

  • D. Defective bile salt synthesis from enzyme deficiency alone

    Isolated defects of bile salt synthesis are not the usual cause of ductal brown stones.

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 Pathology question

What is the answer to this Pathology question?

The best answer is C, Bacterial beta-glucuronidase deconjugating bilirubin in infected, stagnant bile. Brown pigment stones form in the bile ducts when bile stasis and infection with enteric bacteria such as Escherichia coli lead to deconjugation of bilirubin glucuronides by bacterial beta-glucuronidase.

Why is "Supersaturation of bile with cholesterol from raised HMG-CoA reductase" not the answer?

Cholesterol supersaturation produces gallbladder cholesterol stones in obese women.

Why is "Intravascular haemolysis increasing unconjugated bilirubin load" not the answer?

Chronic haemolysis causes black pigment stones in the gallbladder.

Why is "Defective bile salt synthesis from enzyme deficiency alone" not the answer?

Isolated defects of bile salt synthesis are not the usual cause of ductal brown stones.

What concept does this question test?

It tests Hepatobiliary: brown pigment stones in Pathology. The insoluble unconjugated bilirubin precipitates with calcium. Parasites such as Ascaris or liver flukes may be associated.

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 Hepatobiliary: brown pigment stones?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.