Proximal aortic thrombosis in a dog

A 6.9-kg, 12-year-old, female, spayed, mixed-breed dog was referred for evaluation of persistent tachypnea, despite multimodal therapy with various antibiotics and glucocorticosteroids. Cranial systemic hypertension with caudal systemic hypotension, left ventricular thickening with mild mitral and aortic regurgitation, and cardiogenic pulmonary edema were detected from initial diagnostic testing at the referral institution. A non-contrast-enhancing lesion involving the thoracic aorta along the ascending aorta, aortic arch, isthmus, and proximal descending aorta causing near-complete occlusion of the aortic lumen was revealed from computed tomography imaging. Conservative management for congestive heart failure was instituted. Due to poor quality of life, the dog was euthanized. On autopsy, the cranial aorta was obstructed by a large chronic organizing thrombus with mild neutrophilic and lymphoplasmacytic aortic arteritis. The heart was enlarged with left ventricular concentric hypertrophy and myocardial fibrosis with secondary congestive heart failure. Renal necrosis and hepatocellular atrophy were presumed secondary to reduced perfusion and hypoxia. The underlying etiology of the thrombus and arteritis was unresolved. Similar pathologic findings have not been reported in dogs to the best of the authors' knowledge. Aortic thrombus should be considered as a differential for a mass-like occlusive lesion in the proximal aorta in the dog.