Anterior bronchus sign

Last revised by Dr Henry Knipe on 25 Apr 2019

The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph.

Gross anatomy

The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly the bronchus is seen end-on as a ring shadow. This occurs ~50% of the time.

Related pathology

The upper limit of the adjacent soft tissue thickness:

  • normal: <3 mm of soft tissue lateral to the bronchus
  • abnormal: >6 mm of soft tissue implies the presences of a mass, and warrants cross-sectional imaging

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Cases and figures

  • Case 1: normal anterior bronchus shadows
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