EP841 - “From Routine to Ruin: When Surgery Turns Catastrophic”

Purpose/Background: The arterial supply of the colon is primarily derived from the superior and inferior mesenteric arteries (SMA and IMA). These arcades may undergo compensatory enlargement in response to reduced mesenteric perfusion. Anatomical variations in the origin and branching patterns of the mesenteric arteries are common, and a thorough understanding of these variations is critical prior to colectomy. Failure to recognize such variants may result in inadequate colonic perfusion, particularly in patients with pre-existing atherosclerotic disease or those who have undergone prior bowel resection. Atherosclerosis is the leading cause of stenosis and occlusion of mesenteric arteries, with the SMA most affected. The prevalence and severity of atherosclerotic involvement increase with age. In elderly individuals, SMA stenosis is observed in 33-60% of cases, while IMA stenosis has been reported in 38-57%.

Methods/Interventions: We present a case of a 75-year-old female who came in with a 2-week history of progressively worsening right lower quadrant pain. The pain was not associated with nausea, emesis, hematochezia, or melena. She never had a colonoscopy. She is a former smoker. Initial imaging with a non-contrast CT scan revealed acute ascending colitis/diverticulitis at the cecum with a 3.7 x 3.8 cm abscess. On physical exam, she demonstrated peritoneal signs. She underwent urgent robotic-assisted right hemicolectomy with intracorporeal ileocolic anastomosis.

Postoperatively, she demonstrated return of bowel function but was unable to tolerate an oral diet. On postoperative day 10, repeat CT imaging revealed pneumatosis intestinalis of the distal small bowel, concerning for bowel ischemia. She underwent an exploratory laparotomy, takedown of the ileocolic anastomosis, resection of approximately 150 cm of small bowel, and creation of an end ileostomy. She was initiated on total parenteral nutrition (TPN), and the ileostomy was initially functional.

Subsequently, the patient developed intractable nausea, multiple episodes of emesis, and declining ostomy output, raising concern for further ischemic insult. A CT angiography of the abdomen demonstrated a prominent inferior mesenteric artery (IMA) with a well-developed arc of Riolan serving as collateral flow. However, the distal segment of this collateral was thrombosed, likely at the site of prior resection. Importantly, both the superior mesenteric artery (SMA) and celiac trunk were found to be completely occluded, indicating that the patient's bowel perfusion had been entirely dependent on retrograde collateral flow through the IMA.

Imaging further revealed extensive pneumatosis involving the stomach, duodenum, and remaining small bowel, consistent with diffuse gastrointestinal ischemia. Vascular surgery evaluation concluded that no revascularization targets were present, and further bowel resection was deemed incompatible with life. The patient was transitioned to hospice care and passed away shortly thereafter.

Results/Outcomes: N/A

Conclusion/Discussion: Preoperative recognition of anatomical variations in colonic vascular supply is critical, particularly in patients with occlusive vascular disease, to minimize the risk of postoperative complications such as anastomotic leakage or ischemia of the residual colon and small intestine. A thorough understanding of the mesenteric vascular anatomy allows the surgeon to anticipate intraoperative variability, accurately plan vascular ligation sites, and optimize the overall surgical approach.

3D view of mesenteric vessels
Image demonstrating enlarged Inferior Mesenteric Artery and Arc of Riolan