Bronchiectasis

Overview

Abnormal IRREVERSIBLE dilatation of bronchi/bronchioles (>2mm), from inflammatory bronchial wall weakening. Cardinal feature: persistent cough + copious FOUL-SMELLING purulent sputum. Post-infectious cases: childhood/early adult.

Etiopathogenesis

Two mechanisms together, nearly always: ENDOBRONCHIAL OBSTRUCTION + INFECTION.

Obstruction (foreign body, tumour, enlarged nodes) → air resorption distal → atelectasis + secretion retention → sets up infection
Infection — secondary to obstruction+impaired defence, OR primary (bronchiectasis from suppurative necrotising pneumonia directly)

Settings:

Hereditary/congenital → DIFFUSE bronchiectasis: congenital bronchial defect; cystic fibrosis (exocrine gland defect → obstruction+infection); hereditary immune deficiency; immotile cilia syndrome incl. KARTAGENER’S (bronchiectasis+situs inversus+sinusitis — microtubule defect, ciliary immotility, male infertility); atopic asthma+family history (rare diffuse)
Obstruction → LOCALISED disease (contrast diffuse): foreign body, endobronchial tumour, hilar node compression, post-inflammatory scarring (healed TB)
Secondary complication of necrotising pneumonia (staph, TB)

Morphology

Distal bronchi/bronchioles beyond segmental bronchi.

Gross: diffuse or segmental. Bilateral LOWER LOBES commonest; LEFT lower lobe (more vertical airways) > right. Pleura fibrotic/thickened/adherent. 4 subtypes: Cylindrical (commonest, tube-like), Fusiform (spindle), Saccular (rounded sac), Varicose (irregular). Cut surface: HONEYCOMBED appearance, dilated bronchi to pleura, thick walls, mucus/mucopus-filled, fibrotic reduced parenchyma.

Micro: epithelium normal/ulcerated/squamous metaplastic. Wall: acute+chronic infiltrate, muscle+elastic tissue DESTROYED→fibrosis. Parenchyma fibrotic, surrounding interstitial pneumonia. Pleura adherent, fibrous bands to bronchus.

Clinical features

Chronic cough+foul sputum, haemoptysis, recurrent pneumonia. Sinusitis common (diffuse disease). Late complications (longstanding uncontrolled): clubbing, metastatic abscess (often brain), amyloidosis, cor pulmonale.

Related: small airways disease (bronchiolitis/bronchiolitis obliterans)

Older paediatric+elderly. Causes: viral (adenovirus, RSV commonest), bacterial/fungal, toxic gas (silo-fillers’), gastric aspiration. Micro: narrow bronchioles occluded by fibrous plugs, inflamed walls (lymphocytes/plasma cells), surrounding interstitial pneumonitis+fibrosis.

Clinical relevance

Obstruction+infection dual mechanism = organising principle for whole etiology list — every cause works via one/both mechanisms; reason through unfamiliar causes by asking which mechanism, don’t just memorise list. Kartagener’s = one structural defect (ciliary microtubule) → apparently unrelated tetrad (bronchiectasis+situs inversus+sinusitis+infertility) — situs inversus occurs because cilia also needed for embryonic left-right patterning, ties anatomic curiosity to same root cause. Diffuse (hereditary/congenital) vs localised (obstruction) = practical reasoning tool — imaging distribution narrows etiologic search before other tests. Late complications (clubbing, brain abscess, amyloidosis, cor pulmonale) = predictable downstream consequences of chronic suppuration, not random — chronic antigen stimulation→amyloidosis, chronic hypoxia→clubbing+cor pulmonale, septic focus→haematogenous spread to brain.

Overview

Bronchiectasis is abnormal, irreversible dilatation of bronchi and bronchioles (>2 mm diameter), developing secondary to inflammatory weakening of the bronchial wall. Cardinal clinical feature: persistent cough with copious, foul-smelling purulent sputum. Post-infectious cases commonly begin in childhood/early adult life.

Etiopathogenesis

The underlying inflammatory-destructive process almost always results from two mechanisms acting together: endobronchial obstruction and infection.

Obstruction (foreign body, neoplastic growth, enlarged lymph nodes) causes resorption of air distal to the block, producing atelectasis and secretion retention — a setup that favours secondary infection.
Infection may be secondary to that local obstruction plus impaired systemic defence (promoting bacterial growth), or may be the primary event — bronchiectasis developing directly from suppurative necrotising pneumonia.

These two mechanisms appear across several clinical settings:

Hereditary/congenital factors (produce diffuse bronchiectasis):
- Congenital bronchiectasis — developmental bronchial defect.
- Cystic fibrosis — generalised exocrine gland secretion defect → obstruction + infection + bronchiectasis.
- Hereditary immune deficiency diseases.
- Immotile cilia syndrome, including Kartagener’s syndrome (bronchiectasis + situs inversus + sinusitis) — ultrastructural microtubule defect causing ciliary immotility across respiratory epithelium, sperm, and other ciliated cells; affected males are often infertile.
- Atopic asthma with positive family allergy history — rarely diffuse bronchiectasis.
Obstruction — produces localised (not diffuse) post-obstructive bronchiectasis, confined to the affected segment; causes include foreign bodies, endobronchial tumours, hilar lymph node compression, post-inflammatory scarring (e.g. healed TB).
Secondary complication of necrotising pneumonia — e.g. staphylococcal suppurative pneumonia, tuberculosis.

Morphology

Characteristically affects distal bronchi/bronchioles beyond the segmental bronchi.

Gross: diffuse or segmental involvement; bilateral lower lobes most frequent, with the left lower lobe’s more vertical airways affected more than the right. Pleura fibrotic, thickened, adherent to chest wall. Four gross/bronchographic subtypes:

Cylindrical — most common; tube-like dilatation.
Fusiform — spindle-shaped dilatation.
Saccular — rounded, sac-like distension.
Varicose — irregular enlargements.

Cut surface of affected (usually lower) lobes shows a characteristic honeycombed appearance — extensively dilated bronchi reaching nearly to the pleura, thickened walls, lumina filled with mucus/mucopus; intervening parenchyma reduced and fibrotic.

Microscopy (fully-developed disease):

Bronchial epithelium normal, ulcerated, or squamous-metaplastic.
Bronchial wall infiltrated by acute and chronic inflammatory cells; destruction of normal muscle and elastic tissue, replaced by fibrosis.
Intervening lung parenchyma fibrotic; surrounding lung shows interstitial pneumonia changes.
Pleura adherent, with fibrous bands bridging bronchus and pleura.

Clinical Features

Chronic cough with foul-smelling sputum, haemoptysis, recurrent pneumonia. Sinusitis commonly accompanies diffuse disease. Late complications in longstanding, uncontrolled disease: finger clubbing, metastatic abscesses (often to the brain), amyloidosis, cor pulmonale.

Related: Small Airways Disease (Bronchiolitis/Bronchiolitis Obliterans)

Inflammatory small-airway disease, predominantly in older paediatric and elderly patients. Causes: viral infection (adenovirus, RSV most frequent), bacterial/fungal infection, toxic gas inhalation (silo-fillers’ disease), gastric content aspiration. Microscopy: narrowed bronchiolar lumina occluded by fibrous plugs; inflamed walls infiltrated by lymphocytes/plasma cells; surrounding alveoli show interstitial pneumonitis and fibrosis.

Clinical Relevance

The obstruction-plus-infection dual mechanism is the organising principle for the entire etiology list — every listed cause (cystic fibrosis, immotile cilia, post-obstructive scarring, necrotising pneumonia) works by producing one or both of these two effects, so a new or unfamiliar cause of bronchiectasis can be reasoned through by asking which of the two mechanisms it triggers, rather than memorised as an independent fact.
Kartagener’s syndrome is a clean illustration of one structural defect (ciliary microtubule abnormality) producing an apparently unrelated triad (bronchiectasis, situs inversus, sinusitis, plus male infertility) — situs inversus occurs because normal cilia are also required for correct left-right patterning during embryogenesis, tying an anatomic curiosity to the same root cause as the respiratory and fertility findings.
The diffuse-versus-localised distinction (hereditary/congenital causes producing diffuse disease, obstruction producing localised disease confined to a segment) is a practical clinical reasoning tool — the distribution pattern on imaging itself narrows the etiologic search before any other test is done.
Bronchiectasis’s late complications (clubbing, metastatic brain abscess, amyloidosis, cor pulmonale) are not random associations but the predictable downstream consequences of chronic suppuration — chronic antigenic/inflammatory stimulation drives amyloidosis, chronic hypoxia drives clubbing and cor pulmonale, and the septic focus itself is the source for haematogenous spread to distant sites like the brain.

Obstruction-plus-infection dual mechanism mapped against the major clinical settings that cause bronchiectasis
Four gross subtypes (cylindrical, fusiform, saccular, varicose) compared