Evaluation of Multiple Embolic Agents for Embolization of the Superior Rectal Artery in an Animal Model

Abstract

To prospectively compare the safety of transcatheter embolization of superior rectal arteries in healthy pigs with multiple agents such as coils, spheres and liquids. Nine adult domestic pigs (three males, mean weight: 60kg [50-70]) were randomly assigned to the embolization group: copolymer of ethylene vinyl alcohol (EVOH)-Onyx® (group 1, n = 3), microspheres 500µ (group 2, n = 3), 2-mm micro-coils (group 3, n = 3). After a selective angiogram has been acquired, the embolic agent was infused at the distal part of rectal arteries. An angio-CT was performed before and after each embolization. After one week, angiography was repeated prior to euthanasia. At necropsy, the anorectal juncture was removed for histopathologic examination. At necropsy, 100% of animals embolized with Onyx developed a significant necrosis zone of the distal part of the rectum. Histological examination revealed a mural infarction. For the micro-coil and microsphere groups, gross examination of the intestines did not reveal any evidence of ischaemia. The coils were found in the distal arterial vasculature of the meso-rectum, allowing a downstream revascularization by collaterals. The microspheres and onyx in the rectal wall, more distally. Microspheres appear to induce fewer histologic complications than the liquid embolic agent and provide a more distal occlusion than micro-coils. These results suggest that, for superior rectal artery embolization, a super-selective embolization using spheres in human clinical conditions should be more effective and as safe as coil embolization. EVOH might be an unsafe embolization agent for haemorrhoids.