Persistent Right Aortic Arch
Persistent right aortic arch is the most common vascular ring anomaly in dogs (German Shepherds and Irish Setters in particular) and has also been reported in cattle, horses, and cats. The right aortic arch fails to regress normally, resulting in entrapment of the esophagus and trachea at the level of the heart base. The structures are encircled by the persistent arch on the right, by the ligamentum arteriosum on the left and dorsally, and by the base of the heart ventrally. The esophagus is typically compressed, leading to the most common clinical sign of regurgitation (often noted at weaning). Aspiration pneumonia is common in affected animals. Surgery is recommended to transect the ligamentum arteriosum to free the esophagus from entrapment. Radiographically, right-ward deviation of the trachea on dorsoventral or ventrodorsal view is highly sensitive and specific for the diagnosis of persistent right aortic arch. CT can confirm the diagnosis before surgery and assist surgical planning.