Tracheomegaly

Martha Huller Maier, MD

Key Facts

Terminology

Dilatation of trachea and central bronchi with relatively abrupt transition to normal caliber of peripheral airways

Imaging Findings

Trachea and 1st- through 4th-order bronchi affected
Diagnosis often overlooked
- Men: Tracheal transverse diameter > 25 mm, sagittal diameter > 27 mm
- Women: Tracheal transverse diameter > 21 mm, sagittal diameter > 23 mm
CT: Dilatation may also be overlooked
- Hint: Trachea may be bigger than ascending aorta

Top Differential Diagnoses

Pathology

Clinical Issues

Presentation variable: Asymptomatic to severe respiratory symptoms
More common in 3rd or 4th decades
- Rarely diagnosed in infancy or childhood even though considered congenital
Smoking cessation extremely important
Conservative treatment: Chest physiotherapy to clear secretions and antibiotics for infections

Axial CECT shows an enlarged trachea

and multiple tracheal diverticula

. Paraseptal emphysema

is also extensive.

Lateral radiograph shows the typical radiographic features of a dilated trachea (28 mm) due to tracheobronchomegaly

. The trachea is as wide as the vertebral bodies

TERMINOLOGY

Abbreviations and Synonyms

Mounier-Kuhn syndrome, trachiectasis, megatrachea, tracheobronchiectasis, tracheocele, tracheobronchopathia malacia

Definitions

Dilatation of trachea and central bronchi with relatively abrupt transition to normal caliber of peripheral airways

IMAGING FINDINGS

General Features

Best diagnostic clue
- Enlarged luminal diameter of trachea and central bronchi
- Tracheal diverticulosis: Irregular, corrugated, scalloped, or undulating appearance of trachea
  - Often overlooked on radiographs or CT
Patient position/location
- Trachea and 1st- through 4th-order bronchi affected
  - May extend as high as the larynx
- Airways distal to 4th- and 5th-order bronchi usually normal in diameter
  - Exception: Repeated infection associated with the disease may eventually lead to distal bronchiectasis
Size
- Women: Tracheal transverse diameter > 21 mm, sagittal diameter > 23 mm
  - Transverse diameter right mainstem bronchus > 19.8 mm, left mainstem bronchus > 17.4 mm
- Men: Tracheal transverse diameter > 25 mm, sagittal diameter > 27 mm
  - Transverse diameter right mainstem bronchus > 21.1 mm, left mainstem bronchus > 18.4 mm
- Measurements reflect 3 standard deviations above the mean
Morphology
- Diffuse luminal enlargement of affected airways
- Airway walls are thinned, atrophic, and abnormally weak
- Tracheal diverticulosis due to
  - Muscular and elastic atrophy in cartilaginous and membranous portions of trachea and bronchi
  - Mucosa, submucosa herniate between tracheal ring causing protrusions ranging in size from several mm to cm
  - Bronchoscope may easily enter these herniations
  - Pooled secretions may give rise to chronic infection

CT Findings