Case Report: Delayed coil migration after endovascular embolization of an inferior mesenteric arteriovenous malformation

Background Inferior mesenteric arteriovenous malformation (IMAVM) is an exceptionally rare vascular lesion. Endovascular embolization is frequently selected as first-line therapy; however, long-term outcomes and delayed complications remain poorly defined. Case summary A 43-year-old woman presented with a 1-year history of progressive fatigue and a 6-month history of intermittent lower abdominal pain and hematochezia, with worsening bright red rectal bleeding over the preceding 3 days. Ten years earlier, she had undergone endovascular embolization for an abdominal vascular malformation at another hospital. Computed tomography angiography (CTA) demonstrated extensive serpiginous abdominopelvic vessels, marked venous dilatation and suspected metallic material within the intestinal lumen. Colonoscopy subsequently revealed a circumferential sigmoid ulcer with luminal stenosis, fistulous openings, and intraluminal exposure of metallic embolization material. Digital subtraction angiography (DSA) demonstrated an extensive high-flow inferior mesenteric arteriovenous malformation (IMAVM), characterized by a diffuse nidus of numerous tortuous abnormal vessels involving the sigmoid mesocolon and adjacent pelvic and retroperitoneal regions. The lesion was predominantly supplied by branches of the inferior mesenteric artery, with early venous drainage through the markedly dilated left ovarian and renal veins into the inferior vena cava. Persistent opacification and recanalization of vessels previously treated by coil embolization were also observed. Ongoing hemorrhage and progressive anemia necessitated emergency hybrid surgery, including resection of the AVM nidus, left renal vein angioplasty, involved bowel segments, excision of the left ovarian venous aneurysm, Hartmann's procedure, and small-bowel anastomosis. The patient recovered uneventfully and remained asymptomatic at the two-year follow-up. Conclusion Delayed coil migration into the gastrointestinal tract is a rare but potentially life-threatening complication of endovascular embolization for IMAVM, warranting long-term clinical and imaging surveillance. In patients with active bleeding, fistula formation, and extensive vascular or bowel involvement, surgery offers a direct and definitive approach to removing exposed embolic material and treating the associated intestinal and vascular lesions.