Atelectasis (summary)

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

Atelectasis describes loss of lung volume secondary to collapse. It has many causes, the root of which is bronchial obstruction with absorption of distal gas. Atelectasis may be subsegmental, segmental, lobar, or involve the entire lung.

Reference article

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

Summary

  • pathophysiology
    • caused by:
      • bronchial obstruction
        • e.g. inflammation, infection, cancer, foreign body
      • adjacent compression
        • e.g. a lung tumor, vascular cause, large osteophyte
    • results in distal gaseous absorption
      • partial or complete loss of volume distal to the obstruction
      • lung parenchyma collapses down
        • associated volume loss
  • role of imaging
    • confirm lung collapse
      • differentiate from air-space opacification
    • help tod determine the cause (may need CT)
    • assess for complications, e.g. pleural effusion

Radiographic features

Chest x-ray

Atelectasis is another word for lung collapse. The commonest cause is a bronchial obstruction that results in distal gas resorption and a reduction in the volume of gas in the affected lung, lobe, segment or subsegment. As the gas is resorbed, the walls of the alveoli collapse in on themselves and the size of the affected area reduces.

This volume loss is the most important radiographic sign of collapse. If the cause is an obstructing lesion, this may be seen on a plain film.

CT chest

CT allows a more accurate depiction of the involved the lung that is involved. 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 GA.

The CT is often helpful to determine the cause or confirm that there is no proximal obstruction.

Medical student radiology curriculum