Retroperitoneal cysts are uncommon entities of difficult diagnosis because of their insidious symptomatology. Urinary apparatus involvement is quite often the mode of presentation and the reason for calling on the urologist. The origin of many of these retroperitoneal cysts remains practically unknown. Surgery with exeresis is the choice management method. Follow-up is necessary for cystic mesothelioma because of the highly frequent relapses. The outlook of hormonal conservative therapy for relapses appears as a future alternative to treatment.