BRONCHIECTASIS

BRONCIECTASIS

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 (foreign body) or due to defect in dynein arm of cilia (Kartagener's 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 follows destructive inflammation of the bronchial wall.

Pathophysiology

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

Localized vs. Diffuse Bronchiectasis

• Localized bronchiectasis is encountered under the following clinical circumstances:
• Following necrotizing pneumonia
  Obstructive lesion
  Tuberculosis (dry bronchiectasis)
  Allergic bronchopulmonary aspergillosis
• Diffuse bronchiectasis is encountered in:
• Cystic fibrosis
  Immobile Cilia Syndrome (Kartagener's Trial)
  IgA deficiency
  Hypogammaglobulinemia
  Childhood infections

Clinical Features

• Clinically characterized by postural cough and expectoration of large quantities of foul smelling sputum with three characteristic layers. Foul smell is due to anaerobic infection. The three layers are purulent sediment, clear middle liquid and top foamy layer. Bronchiectatic segments are insensitive and do not provoke cough. When the patient bends down the gravity moves the pus to proximal normal bronchi evoking a cough response, thus explaining the postural cough.
• Clubbing, coarse persistent leathery rales are seen.
• Chest x-ray is often normal, but can show thickened bronchial walls, multiple cystic spaces with air fluid levels.
• Characteristic dilated bronchi can be demonstrated with high resolution CT. Bronchogram is no longer necessary.
• A combined obstructive and restrictive defect can be seen in PFT's.

Therapy

• Localized bronchiectasis can be cured with resection, if indicated.
• Cyclical antibiotics and postural drainage are the mainstay of therapeutic measures for diffuse bronchiectasis.
• Lung transplant is an option for far advanced cases.