The A.A. present a case report of retroperitoneal spontaneous hematoma and put in evidence the difficulties in making an etiopathogenetic diagnosis of spontaneous renal cyst ropture. The patient was a 72 years old man admitted to the hospital in emergency for a painful ipogastric sintomatology and biliary vomit. The ecography showed a distenced gallbladder and the endoscopy evidenced a duodenal stenosys with compression of the gastric posterior wall, so that we were initially directed towards a pancreatic tumor even if the modest increase of the sierum bilirubinemy and mostly the fact that direct component was almost normal, gave us strong doubts. The spiral TC gave finally the diagnosis of retroperitoneal hematoma and the presence of a bilateral polycistic kidney with several subcapsular cyst, let us suggest, as well as the anamnestic report of a physical stress, a renal origin of the bleeding. A wild literature rewiew did not evidence other similar cases, but the eclusion of other possible causes of retroperitoneal hematoma, suggested this conclusion.