Pneumonia (summary)

Pneumonia refers to infection within the lung and results in infective fluid and pus filling the alveolar spaces. This initially results in patchy airspace opacification and then more confluent consolidation.

Reference article

This is a summary article; read more in our article on pneumonia.

Summary

• epidemiology
  • wide group of affected individuals
• presentation
  • productive cough
  • shortness of breath
  • chest pain
• pathophysiology
  • infection causes exudate to accumulate in the lung
  • this exudate fills the alveolar spaces
    • initially this is incomplete 
    • as the infection worsens, all the air is displaced and the alveoli are filled with infection
• investigation
  • blood workup
    • raised white-blood-cell count and inflammatory markers
  • chest x-ray
    • pneumonia appears as airspace opacificationfirst line investigation
    • confirm infection
    • assess severity and complications
  • CT chest
    • further assessment of complications
    • assessment of complications
      • cavitation and pleural collection can be identifiedcauses in recurrent (non-resolving) infection
  • radiographic features
    • chest x-ray
      • airspace opacification
        • filling of the alveoli with infectious material and pus
        • initially patchy
        • becomes confluent as infection develops
      • air bronchograms
        • air-filled bronchi running through pus-filled alveoli
      • complications
        • pleural collection
        • cavitation
    • CT chest
      • CTairspace opacification
        • looks the same as on a chest x-ray
        • degree of consolidation assessed more accurately
      • complications can be performed for assessment of complicationsseen earlier than chest x-ray
        • cavitation and abscess formationlung necrosis
        • associated pleural collectionscavitation
        • empyema
  • treatment
    • in most cases, antibiotic therapy is all that is required
      • this may be oral or intravenous depending on the severity
      • the CURB score may be used to risk stratify

  Radiographic features

  Plain radiograph

  The main finding that is associated with pneumonia is airspace opacification. This represents filling of the alveoli with infectious material and pus. Initially, this is patchy, but as the infection develops, the amount of residual normal gas-filled alveoli in the area of infection decreases and the airspace opacification on the x-ray becomes increasingly confluent.

  CT

  Consolidation looks the same on CT as it does on an x-ray. The degree of consolidation can be assessed and the complications of pneumonia can be appreciated earlier than with x-ray. These include cavitation and infected pleural collections.

  When CT is performed for infection, it is usually performed following contrast injection.