Left subclavian artery dissection in a dog with coexisting Dirofilaria immitis infection and lymphoma: a case report

An 8-year-old intact male mixed-breed dog presented with a 6-day history of anorexia, lethargy, and vomiting. Antigen testing for Dirofilaria immitis was positive, and circulating microfilaria was detected on a peripheral blood smear. Thoracic radiography showed a normal cardiac silhouette with a generalized bronchial pattern. Abdominal ultrasonography revealed segmental thickening and a loss of layering of the small intestine with marked mesenteric lymphadenopathy. Echocardiography showed heartworms in the main pulmonary artery and an echogenic structure on the right atrial wall. Cardiac computed tomography (CT) angiography (CTA) identified the right atrial structure as a non-enhancing lesion, which was presumed to represent thrombus or granulomatous inflammation. Cardiac CTA confirmed the presence of multiple heartworms and pulmonary thromboembolism and incidentally identified an aneurysmal dilation of the left subclavian artery with a centrally located intimal flap, suggesting an arterial dissection. Abdominal CT revealed a thickened small intestine, fat stranding, and generalized lymphadenopathy. Fine-needle aspiration of a mesenteric lymph node and cytology of the peritoneal fluid confirmed lymphoma. This case presents a rare subclavian artery dissection in a dog with a concurrent heartworm infection and lymphoma and highlights the clinical value of a cardiac CTA protocol for precise visualization of the cardiac and vascular walls.