Ultrasonographic and CT Features of a Neoplasia-Associated Visceral Arteriovenous Fistula in a Cat.

An 11-year-old neutered male European Shorthair cat presented with progressive weight loss, polyuria/polydipsia, lethargy, and recurrent hemorrhagic cystitis. Abdominal ultrasound revealed tortuous and dilated vessels with spontaneous echo-contrast within the right renal parenchyma. Pulsed-wave Doppler demonstrated continuous flow with pulsatile components within the abnormal vessels, consistent with an arteriovenous communication. Computed tomography (CT) angiography confirmed marked intrarenal vascular dilation, strong arterial-phase enhancement, aneurysmal dilation of the right dorsal renal vein, and early caudal vena cava enhancement. Postmortem histopathology and immunohistochemistry established a diagnosis of renal hemangiosarcoma. This represents the first reported case of visceral arteriovenous fistula secondary to neoplasia in a cat.