Left lower lobe collapse
Updates to Article Attributes
Left lower lobe collapse has distinctive features, and can be readily identified on frontal chest radiographs, provided attention is paid to the normal cardiomediastinal contours. However, the shadow cast by the heart does make it more difficult to see than the right lower lobe collapse.
For a general discussion please refer to the article on lobar collapse.
Radiographic features
Chest radiograph
Left lower lobe collapse is readily identified on a well penetrated-penetrated film of a patient with a normal sized heart, but can be challenging in the typical patient with collapse, namely unwell patients, with portable (AP) often under-penetrated films, often with concomitant cardiomegaly. Features to be observed include 1-3:
- triangular opacity in the posteromedial aspect of the left lung (retrocardiac sail sign)
- edge of collapsed lung may create a 'double cardiac contour'
- left hilum will be depressed
- flat waist sign
- loss of the normal left hemidiaphragmatic silhouette
- loss of the outline of the descending aorta
Non-specific signs found in left sided-sided atelectasis are usually also present including:
- elevation of the hemidiaphragm
- crowding of the left
sided-sided ribs - shift of the mediastinum to the left
On lateral projection, the left hemidiaphragmatic outline is lost posteriorly and the lower thoracic vertebrae appear denser than normal (they are usually more radiolucent than the upper vertebrae) 3.
Differential diagnosis
The characteristic shape associated with volume loss usually does not allow for any significant differential diagnosis. As always one should consider:
- consolidation (of the medial basal segment of the left lower lobe)
- pulmonary or posterior mediastinal mass
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