Right lower lobe collapse

Last revised by Dr Pradosh Kumar Sarangi on 17 Apr 2022

Right lower lobe (RLL) collapse has distinctive features, and is usually relatively easily identified. The smaller overlying heart shadow obscures less lung compared with left lower lobe collapse

Findings of lower lobe collapse can be grouped together as they are almost identical on both sides.

For a general discussion please refer to the article on lobar collapse.  

Collapse of the right lower lobe is usually easily identified but can be missed if collapse is profound (which may occur when consolidation is absent), or if the patient is rotated. Features include: 1-3:

  • triangular opacity in the right lower zone (usually medially) with the apex pointing towards the right hilum
  • obscured medial right hemidiaphragm
  • inferior displacement of the right hilum
  • obscured descending interlobar pulmonary artery 
  • distinct right heart border in contact with normal middle lobe
  • inferior displacement of the horizontal fissure

Non-specific signs indicating right sided atelectasis may also be present. 
They include:

  • elevation of the right hemidiaphragm
  • crowding of the right sided ribs
  • shift of the mediastinum to the right
  • ipselateral hypertransradiancy and wider spacing of blood vessels due to compensatory hyperinflation of the right upper and middle lobes
  • superior triangle sign

On the lateral projection the findings are usually obvious:

  • triangular opacity in the lower posterior chest
  • posterior right hemidiaphragm obscured
  • increased attenuation over the lower thoracic vertebrae, (reversing the normal pattern of decreased attenuation compared with the upper thoracic vertebrae) 3
  • oblique fissure displaced posteroinferiorly
  • invisible oblique fissure on lateral CXR if profound collapse rotates the fissure posteromedially (non-tangential to the x-ray beam) 2
  • inferior displacement of the right hilum

If there is an obstructing lesion in the bronchus intermedius, there will be signs of both RML and RLL collapse.

  • triangular opacification in axial images, thinner at the hilum, against the posterior mediastinum/spine and medial hemidiaphragm 2
  • oblique fissure pulled posteriorly and may rotate posteromedially 2
  • compensatory hyperinflation of the right upper and middle lobes 2

The features of right lower lobe collapse are distinctive, however consider:

  • combined right middle and lower lobe collapse if the heart border is obscured
  • consolidation of the medial basal segment of the right lower lobe
  • pulmonary or posterior mediastinal mass

This location is also common for pulmonary sequestration

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Cases and figures

  • Figure 1: position of RLL
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  • Figure 2: position of RLL
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  • Case 1: annotated 
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  • Case 1: annotated  
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  • Case 3: collapse and consolidation
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  • Case 4
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  • Case 2: collapse and consolidation
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