Pneumonia Overview

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Pneumonia - Introduction and Classification

Acute fibrinous pneumonia (Image sourced from Bristol Biomed Image Archive with permission)
Acute exudative pneumonia (Image sourced from Bristol Biomed Image Archive with permission)
Acute exudative pneumonia (Image sourced from Bristol Biomed Image Archive with permission)
Acute necrotising pneumonia (Image sourced from Bristol Biomed Image Archive with permission)
  • Pneumonia
    • Inflammation that takes place in the alveoli and their walls
    • Can be grouped either according to
      • Nature of the inflammatory process
      • Aetiological agent
      • Pattern of the lesion


Bronchointerstitial Pneumonia

Lobar Pneumonia

Interstitial Pneumonia

Embolic Pneumonia

Granulomatous Pneumonia

Verminous Pneumonia

Stages of pneumonia

  • Regardless of the pattern, all pneumonias pass through three stages:
    • Exudative phase
      • In this initial stage inflammatory exudate pours into alveolar spaces and alveolar capillaries are congested
      • Type I alveolar epithelial cells are highly sensitive to injury and cannot proliferate in response to injury
      • Necrosis and sloughing of injured type I cells, denuding alveolar spaces of lining epithelium
      • Neutrophils begin to enter alveolar spaces distended with inflammatory oedema
    • Proliferative phase
      • Type II alveolar cells (less sensitive to and can proliferate in response to injury) begin to proliferate within 24 hours and eventually line the alveolar walls denuded of type I cells ***By 6 days cuboidal type II cells can completely line the alveoli
      • Proliferation of type II cells marks the shift from the exudative to the proliferative stage of pneumonia, also heralded by decreased blood flow in alveolar capillaries
      • Because the original squamous type I cells have been replaced by cuboidal type II cells, the microscopic appearance of pneumonic lungs at about 1 week has been described as “alveolar epithelialization”, “alveolar adenomatosis”, or “bronchiolisation of alveoli”
    • Repair phase
      • Resolution of pneumonia is accomplished by transformation of type II cells to type I cells

Pulmonary Abscesses

Infectious causes of pneumonia

Dogs Canine distemper usually secondary Blastomyces dermatitidis Angiostrongylus vasorum
. Infectious canine tracheitis bronchopneumonia: Bordetella bronchiseptica, Staphylococci, Streptococci, Coliforms Histoplasma capsulatum Toxoplasma gondii
. Herpes virus . . .
Cats Feline calicivirus bronchopneumonia: Pasteurella sp., Streptococcus spp. . Aelurostrongylus abstrusus
. . Feline chlamydiosis . .
Horses Equine rhinopneumonitis Strangles Pneumocystis carinii Parascaris equorum
. Equine influenza Glanders . .
. Equine viral arteritis Rhodococcus equi . .
Cattle Parainfluenza- 3 Necrotic Laryngitis . Dictyocaulus viviparus
. . Pneumonic pasteurellosis . .
. . Contagious bovine pleuropneumonia . .
. . Enzootic pneumonia of calves . .
. . Acute exudative pneumonia . .
. . Mycoplasmal pneumonia . .
. . Mycobacterium bovis - tuberculosis . .
. . bronchopneumonia: Pasteurella sp., Corynebacterium pyogenes . .
Sheep Maedi Visna bronchopneumonia: Corynebacterium pyogenes . Muellerius capillaris
. Parainfluenza- 3 Enzootic pneumonia of lambs . .
. Sheep Pulmonary Adenomatosis Pseudomonas (Malleomyces) pseudomallei . .
Pigs Inclusion body rhinitis Enzootic pneumonia of pigs . Ascaris suum
. Swine influenza Actinobacillus pleuropneumoniae . .
. Porcine reproductive and respiratory syndrome Necrotic Laryngitis . .
. Postweaning multisystemic wasting syndrome Pasteurella multocida . .
. Porcine respiratory coronavirus Contagious porcine pleuropneumonia . .
. . Glasser's disease . .
. . Bordetella bronchiseptica . .
. . bronchopneumonia: Pasteurella spp., Corynebacterium pyogenes, also Streptococcus spp., Tuberculosis . .

Other forms of pneumonia

Aspiration Pneumonia

Gangrenous Pneumonia

Lipid Pneumonia

Uraemic Pneumonia

Foetal Pneumonia

Test yourself with the Lungs Pathology Flashcards

Lungs Pathology Flashcards