Anomalous origins of the right subclavian and common carotid arteries in the dog.

Anomalous origins of the right subclavian and common carotid arteries in a 6-month old Alsatian bitch are described. The first vessel to branch from the aortic arch was a short bicarotid trunk which divided into left and right common carotid arteries. The right common carotid artery was partially occluded at its origin and its function and area of supply was taken over by the right vertebral artery. The right subclavian artery branched directly from the aortic arch and passed dorsally to the oesophagus, forming an incomplete vascular ring around the oesophagus. Although the oesophagus was constricted between the vessel dorsally and the trachea ventrally, it did not cause obstruction or dysphagia. The right vertebral artery was exceptionally large.