From WikiVet English
Jump to navigation Jump to search

Acute bronchitis/bronchiolitis

Bronchiolitis (Image sourced from Bristol Biomed Image Archive with permission)
  • Inflammation of the bronchi - bronchitis
  • Inflammation of the bronchioles - bronchiolitis
  • Types... as expected, depending on the severity and type of insult/injury:
    • serous
    • catarrhal
    • purulent
    • fibrinous
    • necrotizing
    • granulomatous
  • Acute inflammation passes through the same stages as in rhinitis
  • Evolution to chronic inflammation may occur following chronic or repeated infections or irritation by parasitic, allergic agents or inhaled substances.

Chronic bronchitis

  • The quantity of mucus is increased following mucus gland and goblet cell hyperplasia
  • The mucosa is thickened due to:
    • mucus gland hyperplasia
    • leukocytic infiltrates
    • lymphocytes, plasma cells, macrophages, eosinophils
    • squamous metaplasia of the lining epithelium (ciliated epithelium replaced by more resistent but relatively non-functional squamous epithelium) - affects mucociliary clearance
  • In dogs
    • Bronchial irritation and mucus hypersectretion causes chronic intractable cough
    • At post-mortem, trachea and lower airways are full of mucoid or mucopurulent exudate
      • Underlying bronchial mucos is thickened, hyperaemic and oedematous
      • May be a coexisting bronchopneumonia
      • Smooth muscle hypertrophy in pulmonary arteries -> pulmonary hypertension -> cor pulmonale

Chronic bronchiolitis

Chronic bronchiolitis (Image sourced from Bristol Biomed Image Archive with permission)
  • Alterations in the bronchiolar fluid and wall, depending on the severity and chronicity of the injury.
  • Normal serous, bronchiolar fluid may become mucoid because of a goblet cell metaplasia associated with the epithelial hyperplasia
  • Mucous is more viscous than serous fluid and therefore may not be cleared from the airways by the usual clearance mechanisms (eg: cystic fibrosis in people - the underlying cause of the airway pathology is the decreased water content of the airway mucous, leading to airway plugging, and increased risk of secondary infection)
  • The normally thin bronchiolar walls can become thickened with fibrous connective tissue and infiltrated by leukocytes (macrophages, lymphocytes, plasma cells, +/- eosinophils).
  • Potential aetiologies
  • Bronchioles are more susceptible to obstruction than bronchi and the epithelium is highly susceptible to injury due to changed anatomy

Sequelae of bronchitis or bronchiolitis

  • Resolution of inflammation, removal of cellular debris and lumenal exudate with minimal mural fibrosis ... return to normal function.
  • Obstruction of the airways following:
  • Plugging of the lumen by mucus, neutrophils and cellular debris
  • Severe thickening of the airway walls
  • Bronchoconstriction following contraction of smooth muscle surrounding the airways eg: hypersensitivity response, asthma +/- hypertrophy of airway smooth muscle
  • Depending on severity can result in:
    • Dyspnoea
    • Increased respiratory noise (crackles, wheezes)
    • Reduced oxygenation, exercise intolerance, lethargy
    • Collapse of areas of the lung (atelectasis)
    • Overinflation of other parts of the lung (emphysema)
    • Chronic cough
    • Pneumonia following inhalation of inflammatory exudate/infectious material within it

Infectious causes of bronchitis or bronchiolitis

Dogs Infectious canine tracheitis Infectious canine tracheitis . Capillaria aerophila
. Canine distemper . . Crenosoma vulpis
. Parainfluenza- 2 . . .
. Canine Adenovirus 1 and Canine Adenovirus 2 . . .
Cats . . . Aelurostrongylus abstrusus
. . . . Capillaria aerophila
Horses Equine influenza . . Dictyocaulus arnfieldi
. Equine Adenovirus Streptococcus equi subsp. zooepidemicus . .
. . Rhodococcus equi . .
. Equine viral arteritis . . .
Cattle Infectious bovine rhinotracheitis subclinical CAR bacillus . Dictyocaulus viviparus
. Parainfluenza- 3 Pneumonic pasteurellosis . .
. Respiratory syncytial virus Necrotic Laryngitis . .
. . Enzootic pneumonia of calves . .
. . Mycoplasmal pneumonia . .
Sheep Parainfluenza- 3 subclinical CAR bacillus . Protostrongylus spp.
. Sheep Pulmonary Adenomatosis Enzootic pneumonia of lambs . Dictyocaulus filaria
Pigs Swine influenza Pasteurella multocida . Metastrongylus spp.
. . Contagious porcine pleuropneumonia . .
. . Glasser's disease . .
. . Bordetella bronchiseptica . .

Test yourself with the Bronchi and Bronchioles Pathology Flashcards

Bronchi and Bronchioles Pathology Flashcards