Retrotracheal space

Last revised by Joshua Yap on 27 Apr 2023

The retrotracheal space (or Raider triangle) is a radiolucent mediastinal space best seen on lateral chest x-rays. It is normally triangular in shape but can vary greatly in size and shape depending on the patient's body habitus and lung volume 1.

The retrotracheal space was first described by Louis Raider (1913-1999) 2 in 1973 4, although he had a hard time finding a journal willing to accept it, as both Radiology and AJR rejected the manuscript. Ben Felson called it Raider's triangle in his Caldwell Lecture in 1986 3

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Cases and figures

  • Case 1: normal lateral chest x-ray
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  • Case 2: obscured by an aberrant right subclavian artery
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