Collapsed membranes within pelvic cyst: What is the diagnosis?

Key Clinical Message Collapsed membranes and daughter cysts are pathognomonic for hydatid cysts on imaging. The comma-shaped lesions, visible within the hydatid cyst in sagittal view of MRI, are collapsed membranes. Although primary hydatid cyst of pelvic cavity is rare, clinicians should remember to include hydatid cysts in differential diagnosis of pelvic cysts.