Post-traumatic peripheral arteriovenous fistula manifesting as digital haemorrhages in a cat: diagnosis with contrast-enhanced 3D CT imaging

Arteriovenous fistulae (AVF) are defined as congenital or acquired abnormal direct communications between an artery and a vein leading to abnormal blood circulation. This report describes an unusual manifestation of acquired peripheral AVF in a cat for which the diagnosis was confirmed by computed tomographic (CT) imaging and three-dimensional (3D) reconstruction. A 10-year-old female spayed domestic shorthaired cat was presented with a 2-month history of nonhealing, crusting, erosive and ulcerative skin lesions on the dorsal right forepaw. Severe chewing and biting, but not lameness, had been reported. Systemic abnormalities were not noted. Histopathology revealed increased numbers of thin-walled and slightly grouped vascular profiles in the superficial and mid-dermis, which were often markedly dilated and partially obscured by prominent hyaline deposits. There were a few pyknotic nuclear fragments and haemorrhages in vascular walls as well as multifocal luminal thrombosis with or without recanalization. Differential diagnoses included progressive angiomatosis with trauma or AVF with secondary regional venous hypertension. Computed tomographic images were acquired using a 16-slice Siemens Somotom Sensation CT scanner, and 3D images were created using the Voxar 3D software. Image reconstruction revealed tortuous aberrant vasculature on the medial aspect of the radius and around the carpus compared to normal vascularization on the contralateral limb. These changes were suggestive of the diagnosis of acquired peripheral AVF. The differential diagnosis for localized, nonhealing, haemorrhagic, crusted, erosive or ulcerative distal extremity skin lesions in cats should include acquired AVF, and diagnosis may be confirmed with contrast-enhanced CT imaging.