Superinfected giant renal hydatid cyst with magnetic resonance imaging and intraoperative correlation

Renal hydatid disease is rare and can mimic a complex renal cyst, abscess, or cystic neoplasm. Preprocedural recognition is essential because inadvertent puncture may cause leakage, dissemination, allergic complications, or infection. A 45-year-old Moroccan man presented with progressive abdominal enlargement and left-sided heaviness. Initial ultrasonography elsewhere showed a giant septated left renal lesion interpreted as a Bosniak II cyst, which subsequently underwent percutaneous puncture. Repeat ultrasonography demonstrated daughter vesicles. Magnetic resonance imaging revealed a 29×28×30 cm left renal cyst with heterogeneous T1- and T2-weighted signal, daughter vesicles, detached membranes, a peripheral low-T2 rim, mild wall enhancement, small gas foci, and heterogeneous diffusion restriction. Surgery demonstrated daughter vesicles and hydatid membranes with purulent material. Histopathology confirmed cystic echinococcosis. Daughter vesicles, detached membranes, and a low-T2 pericyst identify the hydatid origin of a complex renal cyst even when gas, wall enhancement, and restricted diffusion indicate superinfection. Hydatid disease should be considered before puncture or drainage of an atypical renal cyst in endemic regions.