Ileal Arteriovenous Malformation after Laparoscopic Right Hemicolectomy Successfully Treated with Interventional Radiology: A Case Report

Arteriovenous malformations (AVMs) are generally considered congenital vascular anomalies, whereas postoperative iatrogenic AVMs and arteriovenous fistulas (AVFs) are rare. In colorectal surgery, newly detected aneurysm-like mesenteric vascular lesions during postoperative surveillance may be difficult to distinguish from aneurysms, pseudoaneurysms, AVMs, and AVFs. A 75-year-old woman underwent laparoscopic right hemicolectomy for transverse colon cancer. Preoperative contrast-enhanced computed tomography (CT) showed no vascular malformation or aneurysmal lesion. Six months after surgery, surveillance CT revealed a 3.8 mm aneurysm-like lesion in a peripheral branch of the superior mesenteric artery near the anastomotic site. Although the patient was asymptomatic and initially managed conservatively, the lesion enlarged to 6.7 mm over two years. Because a pseudoaneurysm with a potential risk of rupture could not be excluded, angiographic evaluation and treatment were performed. Angiography demonstrated three abnormal vessels arising from a terminal ileal arterial branch, early venous drainage into the ileal vein, and an associated venous aneurysm. The lesion was clinically diagnosed as an ileal AVM, although acquired AVF remained an important differential diagnosis. Transcatheter embolization using n-butyl cyanoacrylate was successful. This case suggests that AVM or AVF should be considered in the differential diagnosis of aneurysm-like mesenteric vascular lesions detected after colorectal surgery.