Aberrant right subclavian artery
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Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are among the commonest aortic arch anomalies.
The estimated incidence is 0.5-2%.
They are often asymptomatic, but around 10% of people may complain of tracheo-esophageal symptoms, almost always as dysphagia, termed dysphagia lusoria 3.
Instead of being the first branch (with the right common carotid as the brachiocephalic artery), it arises on its own as the fourth branch, distal to the left subclavian artery. It then hooks back to reach the right side with its relationship to the esophagus variable:
- 80% posterior to the esophagus
- 15% between esophagus and trachea
- 5% anterior to the trachea
- as can be expected from the embryological development of the artery, the right recurrent laryngeal nerve is usually non-recurrent, entering the larynx directly.
- aneurysmal dilatation (aberrant subclavian arterial aneurysms) of the proximal portion of an aberrant right subclavian artery can occur, a pouch-like aneurysmal dilatation is called a diverticulum of Kommerell
- if there is a retro-esophageal course
- it can get compressed between the esophagus and the vertebra
- the incidence of stenosis/occlusion in this segment is higher
- it can be associated with trisomy 21 5, trisomy 18 and other chromosomal defects.
Lateral radiographs of the chest may show obliteration of the retrotracheal space.
An upper GI contrast study will demonstrate displacement of the contrast-filled esophagus. This displacement by the aberrant vessels produces the so-called bayonet deformity of the aberrant right subclavian artery.
CT and MRI both demonstrate the aberrant branch arising from the distal left aortic arch and coursing rightwards and can define the relationship between the aberrant artery and the trachea and esophagus.
The presence of an aberrant right subclavian artery poses a substantial risk of life-threatening hemorrhage in patients undergoing surgery like esophagectomy. Moreover, the recurrent laryngeal nerve does not follow the orthodox course, which is important in thyroid and parathyroid surgeries 6.
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