Circumflex left aortic arch: a new vascular ring anomaly in dogs

OBJECTIVE To describe the circumflex left aortic arch as a new form of canine congenital vascular ring anomaly leading to esophageal constriction. ANIMALS 3 large-breed dogs of variable age: a 9-month-old entire male German Shepherd Dog-Rottweiler cross, a 17-weekold entire male German Shepherd Dog, and a 9-year-old neutered female Labrador Retriever, seen between April 2022 and May 2023. CLINICAL PRESENTATION Dogs presented for chronic postprandial regurgitation and poor growth. One dog presented for a hard mass on the caudal mandibular region. RESULTS Computed tomography revealed a normal leftward-oriented cranial half and an abnormal caudal half of the aortic arch crossing toward the right dorsal hemithorax leading to esophageal constriction in all dogs. In addition, 1 dog presented with a right patent ductus arteriosus and 1 with an aberrant right subclavian artery. CLINICAL RELEVANCE Circumflex left aortic arch is a newly discovered rare type of congenital vascular ring anomaly in dogs, which presents a similar anatomical derangement to the human form. Clinical signs include postprandial regurgitation and poor growth. Circumflex left aortic arch vascular anomaly cannot be surgically corrected via the left thoracotomy that is commonly used for the more common vascular ring anomalies in dogs. Computed tomography is a useful diagnostic modality for the diagnosis of this condition, detection of concomitant congenital vascular malformations, evaluation of associated pathologies, and surgical planning.