Acquired arteriovenous fistula formation following cephalic vein intravenous catheterisation in a cat

Case summary A 10-year-old male neutered domestic shorthair cat was presented with a 4 month history of slow, progressive swelling and intermittent multifocal bleeding of the distal right forepaw that progressively developed after cephalic vein catheterisation for anaesthesia. The procedure was performed for dental calculus removal. Initial clinical and biopsy (superficial biopsy) findings matched two differential diagnoses: progressive angiomatosis and acquired peripheral arteriovenous fistula (AVF). AVF was suspected based on Doppler ultrasound examination that identified multiple abnormal sinusoidal neoformed branching vessels with turbulent high-velocity flow spectrum at the confluence of the artery and vein, and high-velocity arterialised flow in the vein. Owing to rapid and severe progression of lesions after biopsy, the owner requested amputation of the cat’s limb. A definitive diagnosis of acquired iatrogenic peripheral AVF was based on deep-tissue microscopical evaluation. High numbers of arterioles and venules in superficial and deep dermis embedded in oedematous stroma were connected to dilated and tortuous vessels with irregularly thickened walls in deep dermis and panniculus. Vasculitis and vascular thrombosis and thickening (attributed to local hypertension) were common findings. No bone or muscular invasion were observed. The cat was doing well 3 years after surgery. Relevance and novel information This report describes a case of iatrogenic acquired peripheral AVF following venous catheterisation in a cat, fully documented for the first time by a combination of clinical findings, ultrasound imaging, complete histopathology and follow-up history