What is bronchiectasis? pathology, morphology and types

  What is Bronchiectasis?—Definition, Causes, Pathogenesis, and Key Features

Definition

Bronchiectasis is a chronic, irreversible dilation of the bronchi and bronchioles, caused by destruction of the muscular and elastic components of the bronchial walls. It results from chronic or recurrent infection and airway obstruction, leading to permanent structural damage and impaired mucus clearance.

Key Characteristics

  • Persistent, productive cough

  • Foul-smelling or purulent sputum

  • Recurrent respiratory infections

  • May lead to hemoptysis (coughing up blood) in severe cases

Etiology (Causes)

Cause Description
Infections Recurrent bacterial infections (e.g., TB, pneumonia, measles, pertussis)
Bronchial obstruction Tumors, foreign bodies, or enlarged lymph nodes
Cystic fibrosis (CF) Most common genetic cause, with thick mucus and chronic infections
Immunodeficiency e.g., HIV, IgA deficiency
Primary ciliary dyskinesia (e.g., Kartagener syndrome) → defective cilia impair mucus clearance
Allergic bronchopulmonary aspergillosis (ABPA) Seen in asthmatic or CF patients, due to hypersensitivity to Aspergillus

Pathogenesis

  1. Initial insult: Infection or obstruction → impaired mucus clearance.

  2. Chronic inflammation leads to neutrophil infiltration and release of proteases.

  3. Tissue destruction: Breakdown of elastic and muscular components of the bronchial wall.

  4. Dilation and distortion of bronchi → stasis of secretions → more infections, forming a vicious cycle.

Morphology of Bronchiectasis

1. Gross Features

  • Airways are dilated up to 4 times normal size.

  • Most commonly affects lower lobes, especially basal segments.

  • Bronchi appear as thick-walled, dilated tubes, sometimes visible on the lung surface.

2. Microscopic Features

  • Inflammation and ulceration of bronchial epithelium

  • Fibrosis of bronchial walls

  • Squamous metaplasia in chronic cases

  • Accumulation of neutrophils, lymphocytes, and macrophages

Types of Bronchiectasis (Radiologic Patterns)

Type Description
Cylindrical Uniformly dilated bronchi; most common and mildest
Varicose Irregular bronchi with alternating dilation and constriction
Saccular (Cystic) Most severe: ballooned bronchi with sac-like ends

Clinical Features

  • Chronic productive cough

  • Large volumes of foul-smelling sputum

  • Recurrent infections

  • Clubbing of fingers

  • Hemoptysis (in advanced cases)

  • Crackles and wheezing on auscultation

Complications

  • Respiratory failure

  • Hemoptysis

  • Pulmonary hypertension

  • Cor pulmonale

  • Secondary amyloidosis (rare)

 Summary

Bronchiectasis is a chronic disease marked by irreversible bronchial dilation due to infection, obstruction, or genetic factors. It leads to chronic cough, sputum production, and recurrent infections, often forming a vicious cycle of inflammation and damage.


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