What is bronchiectasis?

What is Bronchiectasis

Bronchiectasis is a chronic respiratory disease characterized by permanent, irreversible dilation of the bronchi with destruction of the elastic and muscular components of their walls, typically resulting from acute or chronic infection. 1, 2

Core Pathophysiology

The disease involves a self-perpetuating "vicious cycle" where chronic bronchial infection leads to inflammation, which impairs mucociliary clearance, causing structural lung damage that further predisposes to infection. 2, 3 This cycle is mediated by:

• Neutrophilic inflammation as the hallmark feature, with neutrophil elastase and collagenase destroying bronchial wall components 2
• Impaired mucociliary clearance leading to mucus stasis and bacterial colonization 2
• Progressive airway injury from recurrent bacterial infections and inflammatory mediators 4

Clinical Presentation

The cardinal symptom is chronic productive cough with sputum production and recurrent respiratory infections. 1, 2 Additional features include:

• Hemoptysis (from increased bronchial arterial proliferation and arteriovenous malformations) 4
• Dyspnea and breathlessness (from airflow obstruction and impaired gas transfer) 2
• Clubbing in some cases 2
• Physical examination may reveal rhonchi, crackles, or be entirely normal 1

Diagnostic Approach

High-resolution CT (HRCT) scanning is the diagnostic procedure of choice, with sensitivity and specificity exceeding 90%. 1, 4 The diagnosis requires both:

1. Clinical symptoms (cough, sputum production, recurrent infections) 2
2. Radiological confirmation of permanent bronchial dilation on CT 2

Key HRCT findings include:

• Signet ring sign: enlarged internal bronchial diameter where bronchi appear larger than accompanying arteries 1, 4
• Failure of larger airways to taper toward lung periphery 1, 4
• Air-fluid levels in dilated airways 1
• Identification of airways in extreme lung periphery 1
• Indirect signs: bronchial wall thickening, mucoid impaction, focal air-trapping 1

Common pitfall: Routine chest radiographs may miss bronchiectasis; HRCT is essential when clinical suspicion exists despite normal plain films. 1

Underlying Causes

With increased antibiotic use in childhood infections, an increasing proportion of bronchiectasis cases now have identifiable underlying disorders: 1

Common causes include:

• Cystic fibrosis (1 per 2,000-3,000 live births in US/Europe) 4
• Post-infectious damage (severe pneumonia, tuberculosis, pertussis, measles) 1, 4
• Primary ciliary dyskinesia 4
• Common variable immunodeficiency and hypogammaglobulinemia 4
• Allergic bronchopulmonary aspergillosis (causes central cystic bronchiectasis) 4, 5
• Chronic Mycobacterium avium complex infection 1, 4
• Alpha-1-antitrypsin deficiency 4
• Connective tissue disorders (rheumatoid arthritis, Ehlers-Danlos, Marfan syndrome) 4
• Bronchial obstruction (foreign bodies, tumors, broncholithiasis) 4
• HIV infection 1, 4

A systematic search for underlying causes yields a diagnosis in 47% of cases, with important therapeutic or prognostic significance in 15%. 1

Clinical Significance and Prognosis

Bronchiectasis is a progressive condition that can lead to respiratory failure if untreated, with quality of life impairment equivalent to severe COPD. 2 Key prognostic factors:

• Exacerbations are associated with increased inflammation, accelerated lung function decline, and higher mortality 2
• Mortality risk can reach 30% at 1-year follow-up after an exacerbation, particularly with coexisting COPD 2
• Excessive neutrophilic inflammation correlates with increased exacerbation frequency and rapid lung function decline 2

Management Principles

Treatment aims to prevent exacerbations, reduce symptoms, improve quality of life, and halt disease progression: 2

• Airway clearance techniques (chest physiotherapy offers modest benefit in increasing sputum volume) 1, 4
• Long-term antibiotic therapy (oral or inhaled) for pathogen eradication and exacerbation prevention 2
• Bronchodilators to address airflow obstruction 2
• Pulmonary rehabilitation to improve exercise capacity 2
• Treatment of underlying cause when identified (e.g., corticosteroids for ABPA, macrolide-based regimens for MAC infection) 4
• Surgical resection for selected patients with localized idiopathic bronchiectasis causing intolerable symptoms despite maximal medical therapy 1, 4

Early diagnosis and intervention are critical, as bronchial wall dilatation may be reversible in early disease. 2, 4