Bronchiectasis

Bronchiectasis (Image sourced from Bristol Biomed Image Archive with permission)

Permanent, abnormal saccular or cylindrical dilation of bronchi
Accumulation of exudate within the lumen and partial rupture of bronchial walls
Sequel to chronic bronchitis as result of an unresolved persistent bronchopneumonia
Chronic inflammation within the bronchial mucosa and wall -> release of proteolytic enzymes from neutrophils and macrophages -> destruction of supporting structures in the bronchial walls (eg: cartilage, connective tissue) -> weakens the bronchial walls and damages lining mucosal epithelial cells and their cilia (damage to mucociliary escalator)
Atelectasis in the surrounding lung parenchyma results in increased inspiratory effort and increased intrathoracic negative pressure during inspiration
The weakened bronchial walls are less able to 'resist' the negative pressure and therefore dilate excessively.
With time this dilation becomes permanent as a viscous cycle of exudate pooling in the lumen and increased contact of the bronchial walls with the leukocytes further weakens the bronchial walls.
Most severe in cattle (complete lobular septation and lack of collateral ventilation), least severe in dogs (good colateral ventilation), also seen in sheep, goats and pigs
In very severe cases, the bronchial wall is completely destroyed and unrecognisable - an abscess

Test yourself with the Bronchi and Bronchioles Pathology Flashcards