BackgroundCystic artery pseudoaneurysms are rare. It usually occurs as a complication of laparoscopic cholecystectomy, but can arise uncommonly as a complication of acute cholecystitis. Ruptured cystic artery aneurysms present with haemobilia, intraperitoneal or upper gastrointestinal bleeding. We present an unusual case of cystic artery aneurysm presenting as a massive lower gastrointestinal bleed.Case presentationA 47-year-old man was admitted with a thoracic abscess and was noted incidentally on CT to have acute cholecystitis. Subsequently the patient then presented with massive fresh PR bleeding. This was found on CT to be the result of a cystic artery pseudoaneurysm with associated gallbladder fistulation to the hepatic flexure, secondary to cholecystitis. The patient was treated with coil embolisation of the cystic artery made a full recovery and was discharged with a view to performing an elective cholecystectomy.ConclusionCystic artery pseudoaneurysm is a rare complication of cholecystitis which can present as massive lower gastrointestinal haemorrhage secondary to cholecystocolic fistula. Percutaneous embolization is a safe and effective treatment in the acute phase.