Amoebic liver abscess — DTM&H MCQ

Correct answer: E — Amoebic liver abscess

The correct answer is E, amoebic liver abscess. A young man with fever, right upper quadrant pain, travel to Mexico, a solitary right lobe lesion on ultrasound, and positive Entamoeba histolytica serology fits the classic amoebic liver abscess picture: the parasite spreads to the liver via the portal vein from a colonic infection and preferentially forms a single abscess in the right lobe due to portal blood flow patterns. Serology is highly sensitive (over 90 percent) in this condition, and the absence of biliary obstruction argues against an ascending bacterial process. This combination of travel, imaging and serology makes amoebiasis far more likely than any bacterial or neoplastic cause, and directs treatment towards metronidazole rather than antibiotics or drainage alone. Why the other options are wrong: B. Hydatid cyst: Echinococcus produces a well defined cyst, often with daughter cysts or a cartwheel appearance, and relates to exposure to sheep or dogs, not the pus filled lesion with positive amoebic serology described here. A. Hepatocellular carcinoma: This presents as a solid mass in a patient with chronic liver disease or cirrhosis, not an acute febrile illness with positive amoebic serology. D. Pyogenic liver abscess: This is more often multiple, linked to biliary obstruction, diverticular disease or bacteraemia, and would be amoebic serology negative; the stem excludes biliary obstruction and confirms positive serology, pointing away from a bacterial cause. C. Fascioliasis: Fasciola hepatica causes eosinophilia and biliary tract disease after eating watercress, not a solitary liver abscess with positive E. histolytica serology. Key point: A solitary right lobe liver abscess with positive E. histolytica serology after travel to an endemic area is amoebic liver abscess until proven otherwise, treated with metronidazole rather than drainage as first line.

Reference: BNF (NICE), Metronidazole, Indications: Invasive amoebiasis (including amoebic liver abscess) - dosing and treatment guidance, https://bnf.nice.org.uk/drugs/metronidazole/