Incidentally diagnosed non-dissecting thoracic aortic aneurysm in a dog with suspected aortic valve abnormality.

Canine thoracic aortic aneurysm may be underdiagnosed; advanced imaging is essential for detection.

This case report describes an incidentally diagnosed non-dissecting thoracic aortic aneurysm (TAA) in a 12-year-old spayed female Shiba Inu presented for evaluation of anorexia and vomiting. The primary diagnosis was gallbladder mucocele; however, thoracic radiography incidentally revealed cranial mediastinal widening. Subsequent transthoracic echocardiography demonstrated marked dilation of the thoracic aorta distal to the sinus of Valsalva, with a maximal diameter of 30.2 mm, along with abnormal aortic valve morphology characterized by asymmetric cusp motion, eccentric systolic opening, and aortic regurgitation. Computed tomography angiography and intraoperative transesophageal echocardiography confirmed severe circumferential dilation of the aortic root, ascending thoracic aorta, and aortic arch without evidence of dissection or rupture, establishing a diagnosis of fusiform TAA. The dog's gastrointestinal clinical signs resolved following cholecystectomy, and the patient remained clinically stable for over 200 days without specific treatment for the aortopathy. This case highlights that canine TAA may be underdiagnosed, particularly in asymptomatic patients, and underscores the critical role of multimodal advanced imaging—including echocardiography and CT angiography—in identifying aortic pathology. The association between aortic valve abnormality and TAA in this patient mirrors patterns observed in human medicine, suggesting a possible valvulo-aortic relationship in dogs that warrants further investigation.

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