Bronchiectasis refers to an irreversible airway dilation that involves the lung in either a focal or a diffuse manner and that classically has been categorized as cylindrical or tubular (the most common form), varicose, or cystic.
Bronchiectasis can arise from infectious or noninfectious causes (Table 23-1). Clues to the underlying etiology are often provided by the pattern of lung involvement. Focal bronchiectasis refers to bronchiectatic changes in a localized area of the lung and can be a consequence of obstruction of the airway—either extrinsic (e.g., due to compression by adjacent lymphadenopathy or parenchymal tumor mass) or intrinsic (e.g., due to an airway tumor or aspirated foreign body, a scarred/stenotic airway, or bronchial atresia from congenital underdevelopment of the airway). Diffuse bronchiectasis is characterized by widespread bronchiectatic changes throughout the lung and often arises from an underlying systemic or infectious disease process.
TABLE 23-1MAJOR ETIOLOGIES OF BRONCHIECTASIS AND PROPOSED WORKUP ||Download (.pdf) TABLE 23-1 MAJOR ETIOLOGIES OF BRONCHIECTASIS AND PROPOSED WORKUP
|PATTERN OF LUNG INVOLVEMENT ||ETIOLOGY BY CATEGORY (EXAMPLES) ||WORKUP |
|Focal ||Obstruction (aspirated foreign body, tumor mass) ||Chest imaging (chest x-ray and/or chest computed tomography); bronchoscopy |
|Diffuse ||Infection (bacterial, nontuberculous mycobacterial) ||Sputum Gram’s stain/culture; stains/cultures for acid-fast bacilli and fungi. If no pathogen is identified, consider bronchoscopy with bronchoalveolar lavage. |
| ||Immunodeficiency (hypogammaglobulinemia, HIV infection, bronchiolitis obliterans after lung transplantation) ||Complete blood count with differential; immunoglobulin measurement; HIV testing |
| ||Genetic causes (cystic fibrosis, Kartagener’s syndrome, a1 antitrypsin deficiency) ||Measurement of chloride levels in sweat (for cystic fibrosis), α1 antitrypsin levels; nasal or respiratory tract brush/biopsy (for dyskinetic/immotile cilia syndrome); genetic testing |
| ||Autoimmune or rheumatologic causes (rheumatoid arthritis, Sjögren’s syndrome, inflammatory bowel disease); immune-mediated disease (allergic bronchopulmonary aspergillosis) ||Clinical examination with careful joint exam, serologic testing (e.g., for rheumatoid factor). Consider workup for allergic bronchopulmonary aspergillosis, especially in patients with refractory asthma.a |
| ||Recurrent aspiration ||Test of swallowing function and general neuromuscular strength |
| ||Miscellaneous (yellow nail syndrome, traction bronchiectasis from postradiation fibrosis or idiopathic pulmonary fibrosis) ||Guided by clinical condition |
| ||Idiopathic ||Exclusion of other causes |
More pronounced involvement of the upper lung fields is most common in cystic fibrosis (CF) and is also observed in postradiation fibrosis, corresponding to the lung region encompassed by the radiation port. Bronchiectasis with predominant involvement of the lower lung fields usually has its source in chronic recurrent aspiration (e.g., due to esophageal motility disorders like those in scleroderma), end-stage fibrotic lung disease (e.g., traction bronchiectasis from idiopathic pulmonary fibrosis), or recurrent immunodeficiency-associated infections (e.g., hypogammaglobulinemia). Bronchiectasis resulting from infection by nontuberculous mycobacteria (NTM), most commonly the Mycobacterium avium-intracellulare complex (MAC), often preferentially affects the midlung fields. Congenital causes of bronchiectasis with predominant midlung field involvement include the dyskinetic/immotile cilia syndrome. Finally, ...