Tracheal Diverticulum-CT

67 year old smoker with shortness of breath shows: right paratracheal focal air cyst of approximately 3.2 cms length and 1 cm lumen with thin communication to the posterior tracheal wall with no cartilaginous rings. It suggests the uncommon tracheal diverticulum.

Teaching points by Dr MGK Murthy:

Paratracheal air cyst is a nonspecific term used for collection of air parallel to the trachea. Usually it occurs on the right in view of left side being occupied by esophagus.

Absense of alveoli excludes apical hernia or paraseptal bullae or blebs.

Barium swallow / oral contrast  would differentiate Zenker's diverticulum or pharyngocele. Extension from directly below the vocal cords would go in favour of laryngocele.

Presence of azygos fissure would occur along with azygos lobe.

Tracheal diverticulum can be 

a). congenital – possibly represents vestigial supernumerary  lung buds or aborted abnormal buds.

Lined by cartilages.

Small and narrow mouthed.

b). Acquired – Usually in smokers or chronic cough or expiratory obstructive air way diseases.

Majority at D2 level.

Size can varying.

Expand during forced expiration and decreased in inspiration.

Usually due to weakness in the posterior wall with pulmonary functions abnormality.

Lined by respiratory epithileum.

Mounier – Kuhn syndrome consists of multiple tracheal diverticula with marked dilatation of trachea and main bronchi with bronchiectasis and repeated lower respiratory tract infections.