Gross anatomical observations on two cases of right-sided arch of the aorta with the left subclavian artery as its last branch.

Two cases of Adachi-Williams-Nakagawa type N (Krause's type II-2-B) right-sided arch of the aorta were observed gross anatomically. We discovered the first in a 67-year-old female corpse during dissection practice. The second was found in an old male patient through radiography. After his death at 87 years, angiography revealed the anomaly to be of type N. Case 2 (and case 1 after the discovery of the anomaly) were dissected outside of regular dissection practice. Neither belonged to the "circumflexus" type and in each case the ligamentum arteriosum was located on the left, forming a vascular ring. However, only case 1 exhibited marked constriction of the esophagus, explaining the dysphagia that she had suffered. This deviation was evidently caused by projection of the aortic diverticulum of case 1 in front of the vertebral column (since the origin of the descending aorta was located at a more antero-medial position in case 1 than in case 2) and narrowness of the vascular ring of case 1. On both sides in both cases, the second posterior intercostal arteries were branches of the thoracic aorta. This indicated that the high position of the arch of the aorta in both cases (the uppermost point was at the level between Th1 and Th2) is an anomaly, being not limited only to the arch of the aorta. All bronchial arteries originated from the thoracic aorta. These have not been described in association with examples of right-sided arch of the aorta, and were therefore compared against a mirror image of the normal aorta described by Kasai. However, some discrepancies were still noted. Among the veins, the left brachiocephalic vein of case 2 was partially occluded, forming collateral circulation behind the ascending aorta. In both cases, the thoracic duct ascended on the left of the thoracic aorta, passed behind and then above the left subclavian artery, and joined the left angulus venosus. In addition, the azygos vein, recurrent laryngeal nerve, and cardiac nerves are described.