A Case of Massive Lower Gastrointestinal Bleed from a Cystic Artery Pseudoaneurysm Bleeding through a Cholecystocolic Fistula.

BACKGROUND Acute lower gastrointestinal bleeding (GIB) is often associated with favorable outcomes. It is readily diagnosed and managed with colonoscopy, or may resolve spontaneously. Rarely, extra-colonic sources of bleeding may masquerade as lower GIB, posing a diagnostic challenge and potentially lead to harm if there are therapeutic delays. An example is cystic artery pseudoaneurysm, a rare complication of acute cholecystitis and laparoscopic cholecystectomy, which may bleed through a cholecystocolic fistula presenting as lower GIB. CASE REPORT A 66-year-old man with multiple comorbidities including coronary artery disease with multiple stents and peripheral arterial disease presented with massive hematochezia. He was on aspirin 81 mg, clopidogrel 75 mg, and rivaroxaban 20 mg daily. The patient was hemodynamically unstable with BP 77/50 mmHg and heart rate 115 beats/min. Pertinent laboratory investigations showed hemoglobin 10.4 g/dL, WBC 17.2×10³/uL, platelet 437×10³/uL, and INR 1.28. Total bilirubin and liver enzymes were normal. Following prompt volume resuscitation with crystalloids and 2 units of O-negative blood, CT angiogram of the abdomen revealed a ruptured cystic artery pseudoaneurysm bleeding through a cholecystocolic fistula. This developed as a complication of undiagnosed gangrenous cholecystitis. The patient was sent for transcatheter embolization and the bleeding was controlled. The gangrenous cholecystitis was managed conservatively due to the patient's high surgical risk. CONCLUSIONS Although extra-intestinal sources of gastrointestinal bleeding are rare, clinicians should maintain a high index of suspicion, especially in elderly patients presenting concomitantly with right upper-quadrant pain. As delayed diagnosis leads to increased fatality rates, a prompt CT angiogram of the abdomen is pertinent in suspected cases.