Retrocardiac sail sign

Last revised by Frank Gaillard on 11 Feb 2025

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.

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.