Left costocervical vein malformation with anomalous ramification of aortic arch in a dog.

This report describes coexistence of anomalous branches of the aortic arch and the costocervical vein malformation in a German shepherd dog. The first branch of the aortic arch was a bicarotid trunk that divided into the left and right common carotid arteries. The next branch to leave the aortic arch was a common trunk for the right and left subclavian arteries, a bisubclavian trunk, which was immediately bifurcated. The right subclavian artery passed over the esophagus forming a deep groove, so-called incomplete vascular ring on the dorsal wall of the esophagus. Although the esophagus was constricted by the right subclavian artery dorsally and by the trachea ventrally, no clinical symptoms of esophageal obstruction and dysphagia were observed. The left costocervical vein coursed caudoventrally, passed over the aortic arch, and entered the left ventricle. This vessel was much smaller than the right costocervical vein and was partially occluded at its origin.