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

Objective: To prospectively compare the safety of transcatheter embolization of superior rectal arteries in healthy pigs with multiple agents such as coils, spheres and liquids.

Materials and methods: Nine adult domestic pigs (three males, mean weight: 60 kg [50-70]) were randomly assigned to the embolization group: copolymer of ethylene vinyl alcohol (EVOH)-Onyx® (group 1, n = 3), microspheres 500 µ (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.

Results: 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.

Conclusion: 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.