CHEST RADIOLOGY



Case 17:
An adult male presented with mild dysphagia. Following a Plain radiograph a Chest CT was performed. Selected axial post contrast images are shown. What is the diagnosis and what is the dysphagia termed?
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Imaging
Findings


The Contrast Chest CT scan shows a branch arising from the distal left aortic arch which is traveling behind the oesophagus and coursing as the right subclavian artery. This is an aberrant right subclavian artery and sometimes may cause ‘dysphagia lusoria’.


 

Discussion

This is the most common congenital vascular anomaly of the aortic arch (present in about 0.5 to 1% of the population). The right subclavian artery arises just distal to left subclavian artery as the last branch of the aortic arch (beyond the ligamentum arteriosum) and runs to the right POSTERIOR to the esophagus (this produces a posterior indentation from lower left to upper right on barium esophagram). Affected patients are typically asymptomatic, but the condition may cause dysphagia ("dysphagia lusoria"), particularly in patients with a 'Diverticulum of Kommerell'. This is a wide based take-off of the aberrant vessel. A vascular ring encircling both the trachea and esophagus may be completed if there is a ductus associated with the aberrant vessel.

There can be anomalous origin from the proximal descending aorta of either the right or left subclavian artery. An aberrant right subclavian artery arises distal to the left aortic arch. An aberrant left subclavian artery arises distal to the right aortic arch (nonmirror-image right aortic arch); an aortic diverticulum exists at the site of origin. In a right arch with aberrant left subclavian artery, a right-sided ligamentum arteriosum connects the diverticulum and the proximal left pulmonary artery producing a complete vascular ring. In both types of aberrant subclavian arteries, the vessel runs behind the oesophagus. The aberrant right subclavian artery produces an impression on the back of the oesophagus while the left one usually causes anterior displacement and severe compression of the oesophagus. The latter also frequently causes airway compression. The right aberrant artery can be associated with dysphagia in adults while the left usually causes symptomatic airway and oesophageal obstruction during infancy or early childhood.

Plain radiography with barium swallow displays a right-sided aortic arch impression and posterior impression of the aberrant left subclavian on the oesophagus or left-sided aortic arch impression and posterior impression of the aberrant left subclavian artery on the oesophagus. The lateral view also reveals anterior displacement and compression of the trachea by the aberrant left subclavian artery. Thoracic aortography demonstrates the relationship of the arch to the trachea or oesophagus (simultaneous barium swallow) and origin of the aberrant subclavian as the fourth major branch of the aortic arch.

Definitive diagnosis is now usually accomplished by CT or MRI. Both display the severity of airway narrowing and the retro-oesophageal aberrant artery (as seen in the pitures).


Dr Santosh Rai,
Asst Professor, Dept of Radiodiagnosis, KMC Mangalore. Manipal Academy of higher education.
Consultant Radiologist, Global radiology center, WIPRO-MAHE, Bangalore.