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Retrocardiac sail sign

Last revised by Dr Daniel J Bell on 21 Apr 2021

The retrocardiac sail sign represents the characteristic and highly specific appearance of left lower lobe collapse on a frontal chest x-ray.

Radiographic appearance

The collapsed, medially displaced left lower lobe is represented by a triangular area of increased density with sharp margins, superimposed on the heart shadow which resembles the unfurled sail of a yacht.  The heart contours remain preserved (no silhouette sign), while the contour of the left hemidiaphragm is at least partially effaced 1.

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Cases and figures

  • Figure 1: sail boat (photo)
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  • Case 1
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