Paratracheal air cyst

Dr Henry Knipe and Dr Yuranga Weerakkody et al.

Paratracheal air cysts are not an uncommon incidental finding in routine thoracic imaging. They characteristically occur on the right side, in the region of the thoracic outlet.  Occasionally it may mimic pneumomediastinum, so-called pseudopneumomediastinum.

Paratracheal air cysts encompass a number of entities including 9:

There is overlap in the use and description of the terms paratracheal air cyst and tracheal diverticulum in the literature that they often seem to be synonyms for the same entity 9,10

They are present in 3-4% of the population. They may be seen in children and adults with an increased female predilection 4.

Their exact cause is unclear and may be either congenital or an acquired phenomenon. The acquired form is thought to be due to prolonged increased intraluminal pressure, e.g. due to a chronic cough, COPD. 

The cysts may be unilocular or multilocular and do not communicate the trachea. A direct connection with the trachea is visible on CT in ~35% of cases 10, and the term tracheal diverticulum may be used. 

Paratracheal air cysts project posteriorly where the cartilage rings are deficient and usually lies to the right where there is no esophagus supporting the paratracheal tissue. They usually occur at the level of the thoracic inlet

Typically located on the right side at the level of the thoracic inlet. Most measure 3-10 mm and are elongated in shape 5

These are an incidental finding and no treatment is required. The biggest point is to not mistake them for something more sinister. 

Imaging differential considerations include:

Although usually asymptomatic, it may accumulate respiratory secretions that become infected and lead to coughing or tracheobronchitis. 

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Article information

rID: 25783
System: Chest
Synonyms or Alternate Spellings:
  • Paratracheal air cyst (PTAC)
  • Right sided paratracheal air cyst
  • Right sided paratracheal air cysts
  • Paratracheal air cysts
  • Paratracheal gas cysts

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Cases and figures

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  • Case 2
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  • Case 3
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  • Case 4
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  • Case 5
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  • Case 6: left-sided on ultrasound
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