Retrovesical and retroperitoneal extrarenal hydatid cyst: descriptive study of 9 cases.

Objective: To determine the clinical, radiological and surgical features of retrovesical, retroperitoneal hydatid cyst and to discuss the aetiology and pathogenesis. Material and Methods: Nine cases of hydatid cyst operated in the urology department of Charles Nicolle hospital in Tunis between 1982 and 1998 were reviewed: five retroperitoneal sites and 4 retrovesical sites. Results: Retrovesical and retroperitoneal sites represent about 10% of all operations for hydatid cyst in our department. The mean age of our patients was 49.8 years. The clinical presentation was dominated by voiding disorders in the cases of retrovesical hydatid cyst (4 cases) and the appearance of a lumbar or abdominal mass with or without associated abdominal pain in the cases of retroperitoneal hydatid cyst (5 cases). The positive diagnosis was based on abdominopelvic ultrasonography, completed by computed tomography in 3 patients. All patients were treated by wide cyst resection with a favourable course and no recurrence. Conclusion: Retrovesical and retroperitoneal hydatid cysts are rare, but not exceptional in a country with a high endemic rate, such as Tunisia. The diagnosis can be confirmed by radiological investigations. Implantation of the hydatid larva is essentially haematogenous. However secondary implantation in the pouch of Douglas of protoscolex derived from rupture of an intraperitoneal cyst can also be responsible for some retrovesical sites.