Acute gaseous peritonitis after rupture of a retroperitoneal rectal diverticulum in a dog

An 11-year-old, entire male coton de tulear was presented on emergency with acute and severe depression, acute abdominal pain and vomiting of 24 hours duration. Historical complaints included right perineal swelling, dyschezia and tenesmus of 18 months duration. Abdominal ultrasonography and radiography suggested a pneumoperitoneum and positive-contrast colonography showed leakage of contrast medium into the caudal abdomen and the presence of a large retroperitoneal pouch. Exploratory laparotomy allowed the visualisation of faecal leakage from the retroperitoneal space into the peritoneal cavity. Using a perineal approach, a large necrotised rectal diverticulum filled with faeces was found over the retroperitoneal structures. A standard herniorrhaphy was then performed. The dog recovered uneventfully and dyschezia did not recur at the nine month follow-up. Rectal diverticulum rupture associated with peritonitis has not been described in the veterinary literature, to the authors' knowledge, and should be considered as a rare differential diagnosis in dogs being presented with gaseous peritonitis.