A dilated trachea has numerous causes, and in almost all cases represents tracheomalacia (increased size and increased compliance).
As is almost always the case, various diameters have been used. Typical figures include >26 mm in men, >23 mm in women or >30 mm for both genders ref.
Although many of the underlying conditions are congenital, actual dilatation of the trachea and symptomatic presentation are only later in adulthood. Thus the term congenital in the list below refers to the underlying cause, rather than presence of tracheomegaly at birth.
Congenital
Mounier-Kuhn syndrome (tracheobronchomegaly)
-
idiopathic or associated with:
Ehlers-Danlos syndrome (in adults)
cutis laxa (in children)
Acquired
Acquired tracheomalacia is a common finding, seen in approximately 10% of CT and up to 23% of autopsy and bronchoscopy series 5.
Common
prolonged intubation, especially in those with a tracheostomy
chronic obstructive pulmonary disease (chronic bronchitis/emphysema)
diffuse pulmonary fibrosis, especially secondary to radiation
Uncommon
playing wind instruments
inhalation of noxious fumes