Pneumothorax in supine projection

A pneumothorax does not display classical signs when a patient is positioned supine for a chest radiograph as commonly occurs in acute trauma or the critical care setting. Of course, pneumothoraces are common in both these scenarios and even relatively small pneumothoraces may be significant due to the inherent risks of worsening from starting mechanical ventilation.

An erect chest radiograph has a sensitivity as high as 92% for detection of a pneumothorax, whilst a supine projection may only detect 50% 6.

Instead, the pneumothorax may be demonstrated by looking for the following signs:

  • relative lucency of the involved hemithorax
  • deep, sometimes tongue-like, costophrenic sulcus: deep sulcus sign 2
  • increased sharpness of the adjacent mediastinal margin and diaphragm
  • increased sharpness of the cardiac borders or diaphragm
  • visualization of the anterior costophrenic sulcus: double diaphragm sign 3
  • visualization of the inferior edge of the collapsed lung above the diaphragm
  • depression of the ipsilateral hemidiaphragm
  • lumpy appearance of the cardiac contour representing change in shape of the pericardial fat: pericardial fat tag sign

Pitfalls

The subtle signs of a supine pneumothorax may be simulated by other pathologies 5

Usually chest CT or POCUS is done to clarify if there is any diagnostic doubt, although historically additional radiographic projections, e.g. lateral decubitus or apicolordotic, were often performed.

Article information

rID: 4994
System: Chest, Trauma
Section: Signs
Tag: stub, stub
Synonyms or Alternate Spellings:
  • Supine pneumothoraces
  • Occult pneumothoraces
  • Occult pneumothorax
  • Pneumothorax in supine patient
  • Supine pneumothorax

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Cases and figures

  • Figure 1: pneumothorax in supine position
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  • Case 1
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  • Case 2
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  • Case 3: with deep sulcus sign
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  • Case 4: sharp right hemidiaphragm
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  • Case 5
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  • Case 6
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  • Case 7: pericardial fat tag sign
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  • Case 8: bilateral pericardial fat tag signs
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  • Case 9: sharp right hemidiaphragm
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  • Case 10: right apical PTX and skin fold
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  • Case 11: right PTX, sharp diaphragm and retrodiaphragmatic pericardial fat tag sign
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  • Case 12: subtle bilateral PTX with paravertebral hematomata
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