Alveolar echinococcosis: MR findings in the liver

PURPOSE: To clarify the magnetic resonance (MR) imaging findings of alveolar echinococcosis in the liver. MATERIALS AND METHODS: Thirty-five patients with 50 lesions histologically proven to be alveolar echinococcosis were evaluated with MR imaging. Lesions were assessed with regard to the distribution pattern of solid and cystic components and pattern of contrast material enhancement. RESULTS: Cystic components exhibited two patterns at T2-weighted MR imaging: small round cysts and large and/or irregular cysts. Forty-eight lesions (96%) contained small round cysts. Twenty-six lesions (52%) had large and/or irregular cysts. Forty-five lesions (90%) were associated with a solid component. MR imaging characteristics were categorized into five types: multiple small round cysts without a solid component (two lesions [4%], type 1), multiple small round cysts with a solid component (20 lesions [40%], type 2), a solid component surrounding large and/or irregular cysts with multiple small rounds cysts (23 lesions [46%], type 3), a solid component without cysts (two lesions [4%], type 4), and a large cyst without a solid component (three lesions [6%], type 5). In most cases (97%), contrast enhancement was weak. CONCLUSION: The MR findings of alveolar echinococcosis in the liver are multiple small round cysts with a weakly enhanced solid component. The cystic component can be a large and/or irregular lesion, and such lesions are depicted clearly at T2-weighted MR imaging.