Cholecystocolonic fistula with ruptured cystic artery pseudoaneurysm presenting as massive per rectal bleeding: a case report.

Introduction and Importance: Cholecystocolonic fistula and cystic artery pseudoaneurysm are rare complications of gallbladder disease. Their coexistence with massive lower gastrointestinal bleeding is extremely rare and potentially fatal. Case presentation: A 47-year-old male presented with severe acute cholecystitis, followed by massive per rectal bleeding and hypovolemic shock. Contrast enhanced CT revealed a cholecystocolonic fistula with a cystic pseudoaneurysm. The patient underwent emergency open cholecystectomy, primary colon repair, and diversion ileostomy. Postoperative histopathology confirmed chronic cholecystitis without malignancy. The ileostomy was successfully closed 8 weeks later, and the patient recovered well. Clinical discussion: This rare bleeding mechanism may lead to diagnostic delays. Contrast-enhanced CT is crucial for identifying the source of bleeding, while surgery remains the definitive treatment for patients with cholecystoenteric fistulas. Conclusion: This case describes a rare cause of lower GI bleeding. Early identification and timely surgery are crucial to avoiding fatal outcomes.