Peritonitis can result from many causes. We report a case caused by a renal abscess which contaminated the abdominal cavity. A 30-year-old patient was referred with suspected ruptured ectopic pregnancy with signs of peritoneal flooding. The culdocentesis was positive and returned frank pus. Endoscopic exploration with an open laparoscope revealed that the infection did not originate from a gynecological infection but did not identify the exact origin. Laparotomy was performed and revealed a splenic abscess and a subphrenic peritoneal breach releasing a purulent liquid. Splenectomy and abdominal lavage with draining was performed. A post-operative pyelourogram showed a silent kidney with multiple coralliform lithiases. Interventional sonography allowed drainage of a retroperitoneal collection. The post-operative period was uneventful. Left nephrectomy was later performed. Only rare cases of ruptured pyonephrosis leading to peritonitis have been reported, usually with poor prognosis.