Ruptured Superior Mesenteric Artery Pseudoaneurysm With Hemorrhagic Shock Secondary to Infectious Colitis: A Case Report.

Superior mesenteric artery (SMA) pseudoaneurysms are rare, life-threatening vascular abnormalities most often linked to trauma, infection, or iatrogenic injury. Rupture can cause massive hemorrhage and bowel hypoperfusion. We report a unique case of SMA pseudoaneurysm rupture in the setting of infectious colitis, complicated by secondary ischemic colitis. A 66-year-old female with a history of diverticulitis initially presented to the emergency department with abdominal pain and diarrhea, and CT imaging demonstrated non-specific colitis. She was discharged in stable condition with outpatient supportive therapy, but returned three days later with worsening symptoms and hemodynamic instability. CT angiography revealed a ruptured SMA pseudoaneurysm with active intraperitoneal bleeding. Urgent transcatheter embolization was performed, but she subsequently developed bowel ischemia and perforation requiring multiple operations, including right colectomy and small bowel resection. Following a prolonged ICU course, she was ultimately discharged to long-term acute care in stable condition. This case highlights an unusual progression from infectious colitis to vascular catastrophe, followed by ischemic colitis. Early recognition of the potential for septic versus hemorrhagic shock in infectious colitis with hypotension, along with CT angiography and coordinated multidisciplinary management, was critical. Clinicians should maintain suspicion for vascular complications in colitis patients who present with hemorrhage or shock, as early diagnosis and intervention may prevent catastrophic outcomes.