Posterior wall of bronchus intermedius

Last revised by Daniel J Bell on 11 Aug 2018

The posterior wall of bronchus intermedius, also known as the intermediate stem line, is a stripe formed by the interface of the posterior wall of bronchus intermedius and the air within the azygo-esophageal recess 1.

It normally measures between 0.5-2 mm in thickness but is not considered abnormally thickened until it measures greater than 3 mm 1,2. An increased thickness is non-specific but may represent 1:

Radiolographic features

Plain radiograph
  • present on 90-95% of lateral chest x-rays 1 but is only well seen in ~55% of patients 2
  • appears as a vertical or nearly vertical stripe that projects over the lucency created by the left main bronchus and the azygo-esophageal recess 1,2
  • posterior wall of bronchus intermedius is well seen in almost every patient 2
  • it appears as a sharp, well-defined line from the origin of the right upper lobe bronchus 2

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