Case description

An 11-year-old castrated male Tibetan Mastiff was evaluated because of a visibly enlarged blood vessel and progressively worsening swelling of the right hind limb.

Clinical findings

On physical examination, the right hind limb was markedly larger than the left hind limb and the dog was minimally weight bearing on the affected limb. A bruit was auscultated over the affected region. Ultrasonography of the tarsal region of the right hind limb revealed an artery with turbulent flow that communicated with venous drainage. A CT scan confirmed the presence of an arteriovenous malformation (AVM).

Treatment and outcome

Embolization of the AVM with a liquid embolic agent (ethylene-vinyl alcohol copolymer dissolved in dimethyl sulfoxide) was elected. An arteriogram was performed prior to treatment and delineated the vessels that were targeted for embolization. The embolic agent was infused into the AVM, and a postinjection arteriogram confirmed complete occlusion of the AVM nidus and normal arterial flow to the paw with subsequent normal venous drainage. The circumference of the abnormal paw was 51 cm before the procedure and 22.9 cm at 4 weeks after the procedure. Additionally, the gait of the dog dramatically improved. No complications associated with the procedure developed.

Clinical relevance

Peripheral AVMs in dogs are uncommon, and described treatment options are limited and generally associated with serious morbidity. A liquid embolic agent, ethylene-vinyl alcohol copolymer dissolved in dimethyl sulfoxide, was successfully administered in this case, and no morbidity was observed secondary to the procedure. Clinical success was characterized by substantial improvement in limb swelling and marked improvement in the gait of the dog.

A 6-year-old neutered male German shepherd dog was evaluated for obtundation, blindness, and bilateral exophthalmos. A magnetic resonance imaging scan of the brain was performed and identified an arteriovenous malformation (AVM) with several feeding arterial branches, and venous drainage through the cavernous sinus. Venous vessels rostral to the AVM were severely distended and extended into the retrobulbar spaces. Liquid embolization by injection of ethylene vinyl alcohol copolymer was performed from access points in the maxillary arteries and internal carotid arteries. No intraprocedural complications were encountered, and the dog was discharged the next day. Bilateral enucleation eventually was performed because of exposure keratopathy. At 31 months post-embolization, owners reported that the dog was doing very well clinically with high activity level and normal appetite, and the dog also appeared to be pain free. Although intracranial AVMs are very rare in companion animals, successful treatment using liquid embolization is possible and should be considered.