Vascular rings cause primarily respiratory difficulty in humans and swallowing difficulty in animals.  A typical history for a vascular ring anomaly such as persistent right aortic arch is that of a young animal that begins regurgitating shortly after beginning on solid food. Barium esophagrams show varying degrees of esophageal dilation cranial to the heart.  Although tracheal compression also may occur, it is not usually a clinical problem in animals that survive to an age at which they start on solid foods.