What are the types of bronchiectasis?

Types of Bronchiectasis

Bronchiectasis is classified into three morphological types based on radiological appearance (cylindrical, varicose, and cystic), and can be further categorized by distribution (localized versus diffuse) and by underlying etiology. 1, 2

Morphological Classification

The three distinct radiological patterns of bronchiectasis are:

• Cylindrical bronchiectasis - characterized by uniform bronchial dilatation with parallel bronchial walls that fail to taper normally toward the periphery 2
• Varicose bronchiectasis - shows irregular, beaded appearance of the bronchi with alternating areas of dilatation and constriction 2
• Cystic bronchiectasis - demonstrates severe bronchial dilatation with balloon-like or grape-like clusters of dilated airways, representing the most severe form 2

The predominance and extension of these morphological types provide important clinical information, though characterization can be challenging with high interobserver variability. 2

Distribution-Based Classification

Localized Bronchiectasis

• Affects only one lobe and is usually related to focal causes such as bronchial obstruction from tumors, compression by lymph nodes, foreign bodies, or post-pneumonia focal damage 3, 4
• Bronchoscopy is the cornerstone for etiological diagnosis in localized disease 3

Diffuse Bronchiectasis

• Affects two or more lobes and has multiple potential etiologies grouped into five main categories 3:
  • Immune deficiencies (hypogammaglobulinemia, common variable immunodeficiency) 3, 4
  • Genetic disorders causing abnormal mucociliary clearance (cystic fibrosis, primary ciliary dyskinesia, alpha-1-antitrypsin deficiency) 3, 4
  • Autoinflammatory and connective tissue diseases (rheumatoid arthritis, Sjögren syndrome, inflammatory bowel disease) 3, 4
  • Chronic airway inflammatory disorders (allergic bronchopulmonary aspergillosis) or chronic infections (nontuberculous mycobacteria) 3, 4
  • Sequelae of pulmonary insults (prior severe infections like tuberculosis, pneumonia, measles, whooping cough, or radiotherapy) 3, 1

Central versus Peripheral Distribution

• Central bronchiectasis (affecting inner two-thirds of chest) is predominantly seen in allergic bronchopulmonary aspergillosis (ABPA), often bilateral, and is a helpful distinguishing feature as isolated central bronchiectasis occurs in few conditions 1, 5
• Peripheral bronchiectasis can occur alone or in combination with central disease 1

Etiological Classification Systems

ABPA-Specific Classification

The radiological classification for ABPA includes three groups 1:

• ABPA-S (serological ABPA) - without bronchiectasis on imaging 1
• ABPA-CB (ABPA with central bronchiectasis) - presence of central bronchiectasis 1
• ABPA-CB-ORF - central bronchiectasis with other radiological findings 1

Cystic Fibrosis versus Non-Cystic Fibrosis

• Cystic fibrosis-related bronchiectasis (CFRB) - one of the most common identifiable causes in the United States and Europe, occurring in 1 per 2,000-3,000 live births 4, 6
• Non-cystic fibrosis bronchiectasis (NCFRB) - encompasses all other causes, affecting approximately 500,000 people in the US with prevalence increasing substantially with age (7 per 100,000 in ages 18-34 versus 812 per 100,000 in those ≥75 years) 7, 6

Clinical Implications

Diagnostic Approach

• High-resolution CT (HRCT) is essential for diagnosis with sensitivity and specificity exceeding 90%, showing key features including bronchoarterial ratio >1, lack of tapering, and airway visibility within 1 cm of costal pleural surface 1, 8
• After systematic investigation including standardized biological tests and specialized explorations, an etiological diagnosis is obtained in approximately 60% of cases, with up to 38% remaining idiopathic 3, 7

Prognostic Significance

• The extent of bronchiectasis on CT has prognostic value - presence in at least 3 lobes is associated with worse outcomes and included in bronchiectasis severity scores predicting exacerbations, hospitalizations, and mortality 8
• Cylindrical bronchiectasis is generally classified with highest accuracy on imaging, while varicose pattern shows most misclassifications 2