Pneumothorax (summary)

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This is a basic article for medical students and other non-radiologists

Pneumothorax describes gas within the pleural space. This may occur because of a number of reasons and may be spontaneous. Patients will not always be symptomatic and treatment will depend on the cause. Pneumothoraces may be small or very large. The larger the pneumothorax, the more likely it is to cause symptoms.

Reference article

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

Summary

  • pathophysiology
    • gas within the pleural space
    • causes
  • investigation
    • chest x-ray
      • will show most pneumothoraces
    • CT chest
      • will show tiny pneumothoraces not shown on CXR
        • these are often incidental and asymptomatic
      • not used for assessment of pneumothoraces unless complex

Radiographic features

Plain radiograph

A pneumothorax is seen as a region of lucency (dark) around the edge of the lung. This is difficult to see because the lung itself is black too.

However, two rules help to find pneumothoraces:

  • the lung edge
    • you should not be able to see the lung edge
    • if you can, the region peripherally is likely a pneumothorax
  • absence of vessels
    • the lung should have vessels running through it
      • these are white branching structures on the x-ray
    • if there are not vessels, there may be a pneumothorax

If both these findings occur, measure how deep the pneumothorax is and check whether there is any mediastinal shift.

CT

Pneumothoraces on CT are rims of gas (black) around the edges of the lung which may track up the fissures. Very small pneumothoraces can be detected.

Medical student radiology curriculum