Riassunto esame Pneumologia, prof. Centanni, libro consigliato Lung Pathology, Robbins

Bronchiectasis and lung abscess

Definition

Bronchiectasis refers to an irreversible airway dilation involving the lung in a focal or diffuse manner and can be classified as cylindrical/tubular (most common), varicose, or cystic.

Etiology

• Can be caused by infectious or noninfectious causes (different patterns)
• Focal bronchiectasis (localized changes) can be a consequence of extrinsic or intrinsic causes
  • Intrinsic: airway tumor or aspirated foreign body
  • Extrinsic: compression by lymphadenopathy or parenchymal tumor mass
• Diffuse bronchiectasis often arises from a systemic or infectious disease process
• Bronchiectasis location:
  • If upper lung fields: CF or post-radiation fibrosis
  • If lower lung fields: end-stage fibrotic lung disease or immunodeficiency-associated infections
  • If midlung fields: infections by nontuberculous mycobacteria or allergic aspergillosis
• In many cases, however, the etiology is not determined (25-50%)

Epidemiology

• Varies greatly with the underlying etiology
• Generally, it increases with age
• High incidence of malnutrition can predispose to immune dysfunction and development of bronchiectasis

Pathogenesis and pathology

(First three points are for infectious causes, the last point is for noninfectious causes):

• "Vicious cycle hypothesis" = susceptibility to infection and poor mucociliary clearance result in microbial colonization of the bronchial tree (P. Aeruginosa) → presence of the microbes incites continued chronic inflammation → damage to the airway wall → ongoing propagation of the infectious/inflammatory cycle;
• Inflammatory cells in the small airways are known to release proteases, ROS, and proinflammatory cytokines damaging the larger-airway walls + airflow obstruction in the smaller airways;
• α antitrypsin plays an important role in neutralizing the damaging effects of neutrophil elastase and in enhancing bacterial killing → bronchiectasis has been observed in patients with its deficiency;
• In the noninfectious bronchiectasis we have immune-mediated reactions damaging the bronchial wall; traction bronchiectasis arises from parenchymal distortion as a result of lung fibrosis;

Clinical manifestations

• Persistent productive cough with thick sputum
• Physical findings:
  • Crackles and wheezing on auscultation and sometimes clubbing
• Mild-moderate airflow obstruction of pulmonary function tests (such as in COPD)
• Acute exacerbations characterized by changes in nature of the sputum production (↑ volume and purulence)

Diagnosis

• Persistent chronic cough and sputum + radiographic features (in chest X-ray: ↑ Sp if "tram tracks" presence)