Medicine – Bronchiectasis

Bronchiectasis is a chronic respiratory disorder characterised by permanent and abnormal dilatation of the bronchi caused by destruction of the muscular and elastic components of the bronchial walls. Impaired mucus clearance leads to retention of secretions, recurrent infection, and persistent airway inflammation, creating a cycle of further airway damage.

Pulmonary function often demonstrates an obstructive pattern because dilated and damaged airways become narrowed or blocked by retained secretions. However, restrictive or mixed abnormalities can occur when there is extensive associated lung disease.

1. Pathophysiology

Bronchiectasis develops when repeated or severe airway injury damages the bronchial wall and interferes with normal mucociliary clearance.

Secretions accumulate within the affected airways, providing an environment in which bacteria can persist. Recurrent infection causes further inflammation and tissue destruction, resulting in progressively abnormal bronchial dilatation.

This produces a characteristic cycle of:

Impaired mucus clearance → infection → inflammation → bronchial damage → further mucus retention.

Causes of Bronchiectasis

The underlying causes can broadly be divided into congenital or inherited disorders and acquired conditions. In a significant proportion of patients, however, no definite cause is identified.

2. Congenital and Inherited Causes

Selective IgA Deficiency

Selective IgA deficiency can predispose to recurrent respiratory tract infections because IgA plays an important role in protecting mucosal surfaces.

Repeated bacterial infections can eventually damage the bronchial walls and lead to bronchiectasis.

Primary Ciliary Dyskinesia

Primary ciliary dyskinesia is an inherited disorder in which respiratory cilia have abnormal structure or function.

Defective ciliary movement prevents effective removal of mucus and inhaled microorganisms from the respiratory tract. Patients therefore develop recurrent sinus infections, otitis media, chronic productive cough, and bronchiectasis.

Kartagener Syndrome

Kartagener syndrome is a particular phenotype of primary ciliary dyskinesia classically characterised by:

Bronchiectasis + chronic sinusitis + situs inversus.

Situs inversus may include dextrocardia, in which the heart lies predominantly on the right side of the chest.

Male infertility is common because sperm flagella depend on structures similar to respiratory cilia. Female fertility may also be reduced because abnormal ciliary function can interfere with transport through the fallopian tubes.

X-Linked Agammaglobulinaemia

X-linked agammaglobulinaemia, historically called X-linked hypogammaglobulinaemia, causes severe impairment of antibody production.

Affected patients develop recurrent bacterial respiratory infections from childhood. Without adequate treatment, repeated infection can cause permanent airway damage and bronchiectasis.

3. Acquired Causes

Previous Severe Childhood Infection

Severe respiratory infections during childhood can produce permanent bronchial damage.

Classically associated infections include severe bacterial pneumonia, pertussis, and measles, particularly when complicated by significant lower respiratory tract disease.

This form of post-infectious bronchiectasis has become less common in populations with widespread vaccination and improved treatment of childhood infections.

Previous Tuberculosis

Pulmonary tuberculosis can cause substantial destruction and fibrosis of lung tissue.

Following healing, affected areas may develop traction bronchiectasis, particularly in regions of significant pulmonary scarring.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity reaction to Aspergillus, occurring mainly in patients with asthma or cystic fibrosis.

Repeated allergic inflammation and mucus plugging can damage the airways and characteristically produce central bronchiectasis.

Bronchial Obstruction

Bronchiectasis may develop distal to an obstructed bronchus because mucus cannot drain normally from the affected segment of lung.

Causes of obstruction include an inhaled foreign body, endobronchial tumour, or other obstructing lesion.

Localised bronchiectasis confined to one particular lobe or segment should therefore raise suspicion of a focal bronchial obstruction.

Pulmonary Fibrosis

Pulmonary fibrosis can distort and pull open the bronchi as the surrounding lung tissue contracts.

This produces traction bronchiectasis, which is commonly seen on high-resolution CT in fibrotic interstitial lung diseases such as idiopathic pulmonary fibrosis and systemic sclerosis-associated ILD.

Cystic Fibrosis

An important additional inherited cause is cystic fibrosis.

Abnormally thick airway secretions impair mucociliary clearance, resulting in recurrent bacterial infection and progressive bronchial destruction. Bronchiectasis is therefore a major pulmonary manifestation of CF.

Idiopathic Bronchiectasis

Despite appropriate investigation, no underlying cause can be identified in some patients.

This is referred to as idiopathic bronchiectasis.

Clinical Features

4. Chronic Productive Cough

The classic symptom is a chronic productive cough, often producing large quantities of mucopurulent or purulent sputum.

Sputum production may increase substantially during infective exacerbations and may be accompanied by fever, worsening cough, and increasing breathlessness.

5. Exertional Breathlessness

Exertional dyspnoea can occur because of airflow obstruction, mucus plugging, recurrent infection, and progressive loss of functioning lung tissue.

Breathlessness tends to become more prominent when disease is extensive or advanced.

6. Haemoptysis

An important additional feature is haemoptysis.

Chronically inflamed airways develop enlarged and fragile bronchial blood vessels that can bleed. Haemoptysis may range from small streaks of blood in the sputum to potentially life-threatening massive bleeding.

7. Cyanosis

Cyanosis is generally a feature of severe or advanced disease and reflects significant impairment of pulmonary gas exchange.

Patients with advanced bronchiectasis may eventually develop chronic respiratory failure.

8. Finger Clubbing

Digital clubbing can occur in bronchiectasis, particularly when the disease is extensive and associated with chronic suppurative infection.

However, clubbing is not present in every patient.

9. Inspiratory Crepitations

Auscultation commonly reveals coarse inspiratory crackles, particularly over the affected areas.

These may be heard during early or mid-inspiration and can sometimes change following coughing as retained airway secretions move.

Wheezing and rhonchi may also occur when significant airflow obstruction is present.

Diagnosis

10. Chest Radiograph

A chest radiograph may demonstrate thickened bronchial walls, parallel linear or “tram-track” shadows, and ring shadows representing dilated bronchi viewed end-on.

However, a normal chest radiograph does not exclude bronchiectasis, particularly when disease is relatively mild.

11. Pulmonary Function Tests

Spirometry commonly demonstrates an obstructive ventilatory defect, with a reduced FEV₁ and FEV₁/FVC ratio.

A restrictive or mixed pattern can occur when there is extensive bronchiectasis or associated pulmonary fibrosis.

12. High-Resolution CT

High-resolution CT (HRCT) of the chest is the key investigation for confirming bronchiectasis.

Characteristic findings include bronchial dilatation, failure of the bronchi to taper normally, and visible airways close to the pleural surface.

A classic CT sign is the “signet-ring sign,” in which a dilated bronchus has a larger diameter than its accompanying pulmonary artery.

HRCT can also demonstrate mucus plugging, bronchial wall thickening, and the anatomical distribution of disease, which may provide clues to the underlying cause.

Key Clinical Pattern

Think of bronchiectasis in a patient with chronic productive cough, recurrent chest infections, purulent sputum, haemoptysis, coarse inspiratory crackles, and sometimes finger clubbing.

Important causes include previous severe infection, primary ciliary dyskinesia/Kartagener syndrome, immunodeficiency, cystic fibrosis, ABPA, previous TB, bronchial obstruction, and pulmonary fibrosis.

The investigation of choice for confirming the diagnosis is high-resolution CT, which demonstrates permanently dilated, non-tapering bronchi, often with the characteristic signet-ring appearance.