Subcarinal air cysts: multidetector computed tomographic findings.

OBJECTIVE: The purpose of this study was to assess the computed tomographic (CT) features of subcarinal air cysts, which may be related to bronchial diverticula.
METHOD: Seven patients with subcarinal air cysts were retrospectively identified. The following CT features were assessed: location, size, and marginal characteristics of subcarinal air cysts; number, location, and size of communication between the air cyst and bronchi if present; presence of bronchial diverticula in any other location; presence of the pulmonary lesion; and interval change of subcarinal air cysts on follow-up CT.
RESULTS: The air cysts were located inferior or inferoposterior to the carina. The subcarinal air cysts typically had a lobulated margin and demonstrated ductlike communications between the air cyst and bronchi. Ductlike communications arose from the posterointerior aspect of the proximal side of main bronchi and were either solitary or multiple. The larger subcarinal air cysts tended to be multiloculated.
CONCLUSIONS: Subcarinal air cysts may be considered as part of a spectrum of conditions, which include bronchial diverticula and right paratracheal air cysts. Because of their predictable location and appearance, they should be easily distinguished from pathologic lesions such as pneumomediastinum.