Atelectasis (summary)

Last revised by Yuranga Weerakkody on 30 Oct 2021
This is a basic article for medical students and other non-radiologists

Atelectasis describes small areas of collapsed lung. Atelectasis and collapse both describe the same pathophysiology, though atelectasis tends to be used to describe small areas of lung that are not fully expanded, whereas collapse tends to be used to describe larger more confluent areas. 

Reference article

This is a summary article; read more in our article on atelectasis

  • epidemiology
    • varies widely depending on the underlying cause
  • presentation
    • usually breathlessness, but can be asymptomatic and presentation also depends very much on the underlying cause
  • pathophysiology
    • caused by:
      • adjacent compression
        • e.g. a lung tumor, dilated aorta, large osteophyte
      • passive atelectasis
        • when the lung relaxes away from the parietal pleural surface, e.g. pleural effusion, pneumothorax
      • dependent atelectasis
        • in the posterior portions of the lung due to patients not fully expanding their lungs while lying for long periods
  • role of imaging
    • confirm atelectasis
      • differentiate from air-space opacification
    • help to determine the cause (may need CT)
  • treatment
    • management of the underlying cause
    • deeper breathing if the cause is due to hypoventilation

Atelectasis is usually seen on chest x-rays as small volume linear shadows, usually peripherally or at the lung bases. The underlying cause (such as a lung tumor or pleural effusion) may also be visible. Lobar collapse will have a more typical and appearance based on the lobe involved, whereas atelectasis can be more eccentric in position and appearance.

CT allows a more accurate depiction of the involved lung. The dependent lung can be affected by subsegmental collapse just because of lying down (particularly if the patient has been supine for a long period of time, or they are under general anesthesia). This part of the lung is easier to visualize because it is hidden behind the diaphragm on a frontal chest x-ray

CT is often helpful to determine the cause or confirm that there is no proximal obstruction, though most cases of atelectasis are diagnosed and managed without CT investigation. 

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Cases and figures

  • Case 1: bilateral atelectasis
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  • Case 2: segmental atelectasis
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  • Case 3: due to osteophytes
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