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Chronic bronchopneumonia (Image sourced from Bristol Biomed Image Archive with permission)
  • Originates and extends from terminal bronchioles
  • Acute inflammatory exudate initially fills alveolar spaces radiating from the bronchioles causing areas of solidification of lung tissue termed consolidation
  • In bronchopneumonia this consolidation is oriented around terminal bronchioles
  • Most commonly occurs in cranioventral lung lobes and correlates with aerogenous portal of entry and gravitation of infectious droplets
  • Most common form of pneumonia seen in domestic animals and the most common causes are bacterial and mycoplasma infections or aspiration
  • Gross pathology:
    • Affected parts are firmer (consolidated) than surrounding non-affected tissue
    • Colour varies from red to pink to grey depending upon the stage of infection
    • Extent of the lesion varies with the aetiological agent and the lobulation/septation of the species
  • Micro pathology:
    • Early cases centred upon the bronchiolar alveolar junction with exudation, which extends into neighbouring alveoli
    • Exudate contains many neutrophils, macrophages and oedema
    • Alveolar capillaries are hyperaemic
    • Some haemorrhages in severe cases - later stages contain more cells than fluid
  • Spread of the inflammation within the lung is usually by extension from lobule to lobule along the airways, or by necrosis of alveoli and septa in the case of toxin-producing bacteria
  • Sequel to bronchopneumonia:
    • Mild catarrhal inflammation resolves in 7 days and the lung is back to normal within 3 weeks
    • More severe inflammation becomes chronic with fibrosis or bronchiectasis
    • Abscess formation with pyogenic bacteria
    • Pleuritis in severe fibrinous pneumonia with adhesions
    • Death in fulminating cases due to hypoxaemia and toxaemia
  • Suppurative bronchopneumonia
    • Purulent or mucopurulent exudate in airways
    • Generally confined to individual nodules, more obvious in species with prominent lobulation
    • Sometimes referred to as lobular pneumonia
    • Lung colour changes from red to grey to white with time
    • Good exapmle are enzootic pneumonias of cattle, sheep and pigs
  • Fibrinous pneumonia
    • Predominantly fibrous exudate
    • Exudate moves through pulmonary tissue to involve whole lung lobe
    • Sometimes referred to as lobar pneumonia (below)
    • Generally more severe than suppurative pneumonias
    • Externally - severe congestion and haemorrhage, intense red colour with fibrinous plaques
    • May develop into sequestra of necrotic tissue encapsulated by connective tissue
    • Microscopically - massive exudation of plasma proteins into bronchioles and alveoli
    • Rarely resolves completely, leaves scars - pulmonary fibrosis and pleural adhesions