Bronchiectasis is abnormal dilatation of the bronchial tree and predisposes to infection

Abnormal dilatation of main bronchi is termed bronchiectasis Patients have recurrent cough and haemoptysis, and expectorate copious quantities of infected sputum.
Recurrent episodes of chest infection are common, with a mixed flora of organisms including anaerobes.
Although any bronchi may be involved, the most common site is at the base of the lungs. Airways are typically dilated to 5-6 times their normal diameter and may contain purulent secretions.

Histological examination shows chronic inflammation in the wall of the abnormal bronchi, with replacement of the epithelium by inflammatory granulation tissue; it is this which bleeds, giving rise to the frequent clinical sign of recurrent haemoptysis.
In less inflamed areas there is commonly squamous metaplasia of bronchial mucosa.
With repeated episodes of infection extending into adjacent lung parenchyma, there may be fibrous scarring and obliteration of lung, leading to respiratory failure.

Complications of bronchiectasis include chronic suppuration, formation of a lung abscess, haematogenous spread of infection(particularly predisposing to brain abscess), and development of serum amyloid A - derived systemic amyloidosis.