Aberrant origin of the right subclavian artery occurs when the embryological right arch becomes atretic between the origins of the right common carotid artery and the right subclavian artery and is said to occur in between 1/200 and 1/250 persons. The incidence is increased in Tetralogy of Fallot and coarctation of the aorta. The situation is a mirror image of the Type II right aortic arch, with the right subclavian artery arising from the proximal descending aorta. The right ductus almost always disappears and this anomaly is therefore rarely associated with a vascular ring. The origin of the aberrant vessel may be quite dilated, in which case it is referred to as the diverticulum of Kommerell. Occasionally the diverticulum of Kommerell enlarges to the point where it compresses on the esophagus (Fig. 3). Traditionally these have been blamed for dysphagia (dysphagia lusoria), but not all clinicians and investigators accept a causal association. An aberrant right subclavian artery may present as a right supraclavicular mass on the frontal chest radiograph and may be more prone to aneurysm formation than the normally arising right subclavian artery.
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