Flat waist sign

The flat waist sign refers to flattening of the left heart border, specifically the contours of the aortic arch and adjacent pulmonary trunk. It is seen in severe left lower lobe collapse and is caused by leftward displacement and rotation of the heart.

It is different to the straight left heart border sign on CXR seen in hemopericardium secondary to penetrating chest trauma.


Article information

rID: 4898
System: Chest
Section: Signs
Tag: refs, stub, cases
Synonyms or Alternate Spellings:

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Cases and figures

  • Case 1: partial flattening of the left heart border due to LLL collapse
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