Echinococcal Liver Disease
Echinococcal disease is a worldwide zoonosis produced by two main types of larval forms of Echinococcus tape-worms:
- E. granulosus
- E. alveolaris.
- E. granulosus is the causative organism for hydatid cysts.
The typical imaging feature is an intrahepatic encapsulated multicystic lesion with daughter cysts arranged peripherally within the larger cyst. Satellite cysts located exterior to the fibrinous membrane of the main hepatic cyst are not uncommon. Lesions are frequently complex, with mixed high signal intensity on T2-weighted images and mixed low signal intensity on T1-weighted images due to the presence of proteinaceous and cellular debris. The fibrous capsule and internal septations are well shown on T2-weighted images and gadolinium-enhanced T1-weighted images.
E. alveolaris is the causative organism for hepatic alveolar echinococcosis (HAE), a rare parasitic disease for which the fox is the main host of the adult parasite, with dogs and cats being less frequently reported hosts. Pathologically, HAE is characterized grossly by multilocular or confluent cystic, necrotic cavities. A fibrous rim is not present.
Calcification is common in HAE and appears as clusters of microcalcifications or large calcified foci. HAE tends to involve extensive regions in the liver in an infiltrative pattern because it does not form membranes or capsules. HAE is more likely to involve the porta hepatitis causing stenoses of portal veins, intrahepatic bile ducts and hepatic veins, which commonly result in portal hypertension (Balci and Sirvanci 2002).