Huge retrovesical hydatid cyst with pelvic localization as the primary site: a case report.

We present a patient with symptoms of abdominal pain and frequent urination due to a huge mass in the retrovesical region. All imaging modalities revealed a cystic mass containing small daughter cysts located between the urinary bladder and rectum. Its characteristics led us to suspect the presence of a hydatid cyst, and an indirect hemagglutination test for Echinococcus granulosus was found positive. No other involvement of hydatid cystic disease was detected. The primary site for the hydatid disease was therefore regarded as the pelvis, on which only a few cases have been reported previously. The patient started albendazole therapy, but refused operation. Hydatid cyst should always be considered in the differential diagnosis of abdominopelvic masses in endemic regions of the world.