Tracheal Narrowing

Jud W. Gurney, MD, FACR

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Symptoms usually do not develop until tracheal lumen reduced > 50%
- Even with fixed obstruction, symptoms often episodic, leading to misdiagnosis of asthma
Normal tracheal size
- Males: Coronal 13-25 mm; sagittal 13-27 mm; mean 20 mm
- Females: Coronal 10-21 mm; sagittal 10-23 mm; mean 16 mm

Helpful Clues for Common Diagnoses

Extrinsic Compression
- Common etiology: Goiter, vascular rings, mediastinal fibrosis
- Airway wall usually normal (except for mediastinal fibrosis)
- Narrowing often concentric
- May have secondary tracheomalacia
Post-Traumatic Stenosis
- Common causes: Prolonged intubation, penetrating or blunt chest trauma, post-surgery
- Intubation: Location either at tracheal stoma or level of tube balloon
- Airway wall usually thickened
- CT coronal reconstructions more sensitive than axial imaging
Tracheobronchomalacia
- Defined as dynamic decrease in airway luminal diameter of > 70%
  - Crescent or lunate shape with ballooning of posterior tracheal membrane into airway lumen
- May be primary or acquired
- Confident diagnosis requires dynamic CT: Comparison of inspiratory and expiratory luminal diameters
  - Forced expiration or coughing more sensitive than tidal breathing
Saber-Sheath Trachea
- Associated with chronic obstructive pulmonary disease
- Narrow side-to-side diameter, anteroposterior diameter increased
- Extrathoracic trachea normal
- Airway wall thickness normal

Helpful Clues for Less Common Diagnoses

Tracheobronchopathia Osteochondroplastica
- Nodular excrescences of cartilage spare posterior membrane and may be calcified
- Size: 2-3 mm in diameter
- Associated with elderly patients; usually incidental finding at autopsy
Wegener Granulomatosis
- Systemic necrotizing granulomatous vasculitis
- Typical is subglottic narrowing with thickening of airway wall; may be diffuse or focal
- May have thick-walled cavitary lung lesions
Relapsing Polychondritis
- Systemic autoimmune disorder with cartilage destruction
- Airway involvement more common in women (M:F = 1:3); stenosis occurs late
- Airway wall thickening either focal or diffuse and may have increased attenuation
- Spares posterior tracheal membrane
Amyloidosis
- Airway involvement most common form of pulmonary amyloidosis
- Airway involvement most common in localized amyloidosis
- Focal or diffuse nodular soft tissue thickening of airway wall ± calcification/ossification
Laryngeal Papillomatosis
- Due to human papilloma virus
- Younger patients
- May seed lungs with solid to thin-walled cystic nodules
- At risk to develop squamous cell carcinoma (2%)

Helpful Clues for Rare Diagnoses

Tracheal Neoplasms
- Rare tumors, 2/3 either squamous cell carcinoma or adenoid cystic carcinoma
- More likely to have extraluminal extension and mediastinal adenopathy
- Adenoid cystic carcinoma: Longitudinal extent > transaxial extent, and tumor usually more than 180° of airway circumference
- Fat content suggests lipoma or hamartoma
Rhinoscleroma
- a.k.a. Klebsiella rhinoscleromatis
- Chronic granulomatous infection of upper respiratory tract
  - Endemic in Central America and Africa
- Diffuse airway wall thickening, nasal polyps, enlarged turbinates, and thickening nasopharynx common
Complete Cartilaginous Rings
- a.k.a. napkin rings
- Associated with pulmonary artery sling
- Complete rings may be diffuse or focal (most commonly distal trachea)

Alternative Differential Approaches

Focal narrowing
- Extrinsic compression
- Post-traumatic stenosis
- Tracheal neoplasms
- Subglottic narrowing
  - Post-intubation stenosis
  - Wegener granulomatosis
  - Rhinoscleroma
  - Sarcoidosis
Diffuse narrowing
- Tracheomalacia
- Saber-sheath trachea
- Tracheobronchopathia osteochondroplastica
- Relapsing polychondritis
Sparing posterior tracheal membrane
- Relapsing polychondritis
- Tracheobronchopathia osteochondroplastica
Normal wall thickness
- Extrinsic compression
- Tracheomalacia
- Saber-sheath trachea
- Complete cartilaginous rings
Tracheal wall calcification
- Normal process of aging
- Tracheobronchopathia osteochondroplastica
- Amyloidosis
- Relapsing polychondritis
- Long-term warfarin therapy