Definition
Bronchiectasis is a severe, chronic infection of the lung causing pronounced permanent abnormal dilatation of bronchi and bronchioles.

Pathology

• Chronic, necrotizing infection of bronchi in a segment or multiple segments of the lung.
• Infection damages and weakens walls of bronchi so that these structures become markedly dilated and filled with mucous and pus.

Pathogenesis

• The major factors which contribute to the development of bronchiectasis are loss of muco-ciliary clearance system and infection.
• The loss of muco-coliary escalator system can follow either obstruction (foreing body) or due to defect in dyneim arm of cilia (Kertagener syndrome) or due to abnormal mucus (Cystic fibrosis).
• Defect in the clearance mechanism is followed by accumulation of secretions, bacterial overgrowth, infection and atelectasis.
• The chronic infection damages the integrity of the bronchial wall causing dilatation.
• Temporary (6 Weeks) tubular bronchial dilatation occur in all pneumonias.
  
• Saccular bronchiectasis follows destructive inflammation of the bronchial wall.

Pathophysiology

• The muco-ciliary escalator system is destroyed in bronchiectatic segemnts perpetuating accumulation of secretions and infection.
• The bronchiectatic segments are also insensitive thus do not provoke cough untill the pus spills over to normal bronchi.
• Airway obstruction follows diffuse bronchiectasis.
• If there is signifiacant recurrent pneumonias and peribronchial fibrosis a restrive defect can be seen.