Amoebic liver abscess — DTM&H MCQ

Correct answer: C — Metronidazole followed by a luminal amoebicide

The correct answer is C, metronidazole followed by a luminal amoebicide. This man has classic amoebic liver abscess (returned traveller from an endemic area, fever, right upper quadrant pain, solitary right-lobe collection on ultrasound, positive serology despite negative stool microscopy, which is typical since concurrent intestinal carriage is often absent or undetected). Metronidazole is a tissue amoebicide that kills invasive trophozoites in the liver, but it penetrates the bowel lumen poorly, so a luminal agent such as diloxanide furoate or paromomycin is required afterwards to eradicate any residual intestinal colonisation and prevent relapse or continued transmission. This sequential tissue-then-luminal strategy is standard UK practice reflected in the BNF metronidazole monograph for amoebiasis. Why the other options are wrong: E. Ceftriaxone alone for 6 weeks: ceftriaxone has no activity against Entamoeba histolytica and this regimen is designed for pyogenic bacterial liver abscess, not amoebic disease. B. Praziquantel followed by albendazole: these are anthelminthics active against trematodes, cestodes and some nematodes/soil-transmitted helminths respectively; neither has amoebicidal activity against E. histolytica. A. Albendazole monotherapy for 28 days: albendazole is a benzimidazole used for helminth infections such as hydatid disease, not for protozoal amoebic liver abscess, and would not clear tissue trophozoites. D. Immediate surgical resection of the abscess: surgery or aspiration is reserved for diagnostic uncertainty, large abscesses at risk of rupture, left lobe abscesses near the pericardium, or failure to respond to medical therapy within 72 to 96 hours, not as first-line management of an uncomplicated solitary abscess. Key point: amoebic liver abscess is treated medically with a tissue amoebicide (metronidazole) followed by a luminal amoebicide to eradicate gut carriage; drainage and surgery are reserved for complications or non-response.

Reference: BNF (NICE), Metronidazole, Indications and dose: Amoebiasis, medicines.org.uk/bnf; https://bnf.nice.org.uk/drugs/metronidazole/