Tracheal Dilatation
Jud W. Gurney, MD, FACR
DIFFERENTIAL DIAGNOSIS
Common
Upper Lobe Fibrosis
Sarcoidosis
Hypersensitivity Pneumonitis, Chronic
Ankylosing Spondylitis
Overdistension Endotracheal Balloon
Saber-Sheath Trachea
Less Common
Tracheobronchomegaly
Mounier-Kuhn Syndrome
Ehlers-Danlos Syndrome
Tracheal Diverticuli
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Normal inspiratory shape
Round (= coronal and sagittal diameters)
Oval (elliptical shape)
Horseshoe (round anterior contour and flattened posterior membranous wall)
Normal expiratory shape
Horseshoe shape ranging from slight to moderate anterior bowing of posterior tracheal membrane
Anterior convexity of the trachea may be narrow or broad
Tracheal dilatation
Women: Tracheal transverse diameter > 21 mm, sagittal diameter > 23 mm
Men: Tracheal transverse diameter > 25 mm, sagittal diameter > 27 mm
Tracheal index = (coronal diameter)/(sagittal diameter) measured 1 cm above aortic arch: Normal index ∽ 1
Helpful Clues for Common Diagnoses
Upper Lobe Fibrosis
Traction bronchiectasis seen with diseases causing upper lobe fibrosis
Overdistension Endotracheal Balloon
More common with long-term intubation
Causes focal dilitation
Saber-Sheath Trachea
95% have chronic obstructive pulmonary disease (COPD)
Acquired disorder probably related to abnormal intrathoracic pressures
Affects intrathoracic trachea; extrathoracic trachea is normal
Helpful Clues for Less Common Diagnoses
Tracheobronchomegaly
Tracheal wall corrugated due to mucosa herniating between tracheal rings
Central bronchi may be normal or mildly dilated (1st-4th order)
Distal lung may be normal, less common bronchiectasis or pulmonary fibrosis
Tracheal Diverticuli
Mucosal herniation through tracheal wall from increased intraluminal pressure (COPD or professions like horn blowers)
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