Alveolar echinococcosis — DTM&H MCQ

Correct answer: B — Alveolar echinococcosis

The correct answer is B, Alveolar echinococcosis. This is caused by Echinococcus multilocularis, whose definitive hosts are foxes and other wild canids, explaining the occupational fox-trapping exposure and the western China geography, a recognised endemic focus. Unlike the cystic form, alveolar disease grows by infiltrative, tumour-like proliferation within the liver, invading adjacent structures and producing weight loss and a mass that radiologically and clinically mimics cholangiocarcinoma or hepatocellular carcinoma. Diagnosis rests on this infiltrative imaging pattern combined with positive Echinococcus serology (typically Em2plus or recombinant antigen ELISA), and if untreated the disease is progressive and often fatal, so early recognition is essential. Treatment requires prolonged, often lifelong albendazole with radical surgical resection where feasible. Why the other options are wrong: E. Clonorchiasis: Clonorchis sinensis causes biliary tract disease (cholangitis, cholangiocarcinoma risk) from eating raw freshwater fish, not an echinococcal-positive infiltrative mass, and serology here specifically supports echinococcal infection. D. Cystic echinococcosis: Caused by Echinococcus granulosus, this produces well-defined, encapsulated cystic lesions with daughter cysts, typically linked to dogs and livestock, not an infiltrative tumour-mimicking mass associated with foxes. C. Fascioliasis: Fasciola hepatica causes biliary and hepatic parenchymal migration tracks from ingesting contaminated watercress, with eosinophilia and specific fluke serology, not echinococcal serology or a solid infiltrative mass. A. Hepatocellular carcinoma: This is a differential appearance, not the diagnosis, since the serology already confirms an echinococcal aetiology rather than primary liver malignancy. Key point: An infiltrative, cholangiocarcinoma-mimicking liver mass with positive echinococcal serology in someone exposed to foxes points to Echinococcus multilocularis (alveolar echinococcosis), not the cystic form.

Reference: Chouhan MD, Wiley E, Chiodini PL, Amin Z. Hepatic alveolar hydatid disease (Echinococcus multilocularis), a mimic of liver malignancy: a review for the radiologist in non-endemic areas. Clinical Radiology (Royal College of Radiologists), 2019;74:247-256. https://www.clinicalradiologyonline.net/article/S0009-9260(19)30061-3/abstract