Tracheal diverticulum/paratracheal air cysts

Imaging description On CT imaging, collections of extraluminal gas may be present adjacent to the trachea. Most commonly these occur in the right paratracheal region at the level of the thoracic inlet [1–3]. In 8–35% of cases, a connection with the trachea can be observed on CT [1–3]. In cases where the connection is observed, these collections have been termed tracheal diverticula (Figures 1.1 and 1.2). In cases where the connection is not observed, these have been termed paratracheal air cysts (Figure 1.3). However, even when a connection with the trachea cannot be seen on CT, these collections should represent tracheal diverticula. Importance Tracheal diverticula typically arise from the right posterolateral wall of the trachea at the level of the thoracic inlet in 98% of the cases [1]. When a focal air collection is observed in this location, tracheal diverticulum should be the diagnosis. This is especially important in cases of trauma as tracheal diverticula occur in approximately 3% of patients and should not be mistaken for traumatic tracheal injury [1].