Tracheal diverticula are blind-ended outpouchings arising from the trachea. They are usually an incidental finding. Occasionally they can mimic pneumomediastinum. Tracheal diverticula are either congenital or acquired, in the latter case the most common causes are prolonged increased intraluminal pressure, e.g. chronic cough, COPD, tracheomalacia, and iatrogenic (e.g. post-surgical). [from
HPO]