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Define bronchiectasis. Describe its causes, pathogenesis and complications.

Pathology · 2nd Professional — Para-Clinical

Definition

Bronchiectasis is permanent, abnormal dilatation of bronchi and bronchioles, caused by destruction of the muscle and elastic tissue of their walls, usually following chronic necrotising infection.

Permanence is the key word — it distinguishes bronchiectasis from the reversible dilatation seen during acute infection

Causes

Category	Causes
Post-infectious — the commonest in India	Tuberculosis, childhood measles and whooping cough, necrotising pneumonia (Staphylococcus, Klebsiella), adenovirus
Obstruction	Foreign body (a classic cause in children), tumour, mucus plug, enlarged lymph node — gives localised bronchiectasis
Congenital and hereditary	Cystic fibrosis (the commonest cause in the West); primary ciliary dyskinesia; hypogammaglobulinaemia; alpha-1 antitrypsin deficiency
Immunological	Allergic bronchopulmonary aspergillosis — characteristically central/proximal bronchiectasis; rheumatoid arthritis; inflammatory bowel disease
Other	Aspiration; post-transplant; idiopathic

Kartagener syndrome — a subset of primary ciliary dyskinesia; the triad of bronchiectasis, situs inversus and chronic sinusitis, with infertility from immotile sperm; caused by a dynein arm defect

Pathogenesis and Morphology

Obstruction and/or chronic infection → Retained secretions distal to the obstruction become infected → Necrotising inflammation destroys smooth muscle and elastic tissue of the wall → The weakened wall is dilated by traction from surrounding fibrosis and by coughing → Dilated airways drain poorly, so secretions pool and become infected again → A vicious cycle of infection, inflammation and further destruction

Distribution — usually the lower lobes bilaterally and worse distally; upper lobe disease suggests tuberculosis, cystic fibrosis or allergic bronchopulmonary aspergillosis
Shapes — cylindrical, varicose (fusiform) and saccular (cystic)
Microscopy — intense acute and chronic inflammation, ulceration and squamous metaplasia of the epithelium, wall fibrosis, and in severe cases peribronchial abscesses

CLINICAL PEARL

Bronchiectasis is self-perpetuating, and that is what makes it permanent. A dilated, scarred, poorly ciliated airway cannot clear secretions, so it becomes infected; infection destroys more wall; more destruction means worse clearance. Breaking that cycle — by physiotherapy and by treating infection promptly — is the whole basis of management.

Clinical Features and Complications

Chronic cough with copious, foul-smelling, purulent sputum, characteristically worse on changing posture; the sputum separates into three layers on standing
Haemoptysis, sometimes massive, from eroded bronchial arteries
Clubbing, coarse crackles, recurrent fever
Complications — recurrent pneumonia, lung abscess, empyema, metastatic brain abscess, cor pulmonale, respiratory failure, and secondary AA amyloidosis

Applied Aspects

High-resolution CT is the investigation of choice, showing a "signet ring" sign where the dilated bronchus exceeds its accompanying artery, and "tram-track" parallel lines
Management — chest physiotherapy and postural drainage, prompt antibiotics for exacerbations, bronchodilators, treatment of the underlying cause, and vaccination
Surgery is reserved for localised disease with severe symptoms or uncontrollable haemoptysis; bronchial artery embolisation controls massive bleeding
Look for a treatable cause — immunoglobulin deficiency, allergic bronchopulmonary aspergillosis and foreign body are all correctable, and are missed if not sought
Post-tuberculous bronchiectasis is common in India, and full treatment of tuberculosis is therefore also prevention of chronic lung disease

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