Vascular compression of the trachea and oesophgus.

In the developing embryo the foregut is surrounded by a group of vascular structures of bilateral distribution connected with the branchial arches. Portions of these arches are obliterated to form the normally described aorta and great vessels. The ultimate persistence of only one main vascular arch, the left, as the aorta, permits the trachea and oesophagus to lie freely to its right side. Where, however, the vascular obliteration in the embryo stage is abnormal, the residual vessels may so closely surround the trachea and oesophagus that either or both become compressed and symptoms are produced (Fig. 1). The first description of this anatomical abnormality appears to have been made by Hommel in 1737. Quain in his surgical anatomy (1844) gives the following account: