Lobar lung collapse
Lobar collapse refers to the collapse of an entire lobe of the lung. As such it is a subtype of atelectasis (although collapse is not entirely synonymous is atelectasis), which is a more generic term for 'incomplete expansion'. Individual lobes of the lung may collapse due to obstruction of the supplying bronchus.
- compression by adjacent mass
The appearance on chest x-ray varies according to the lobe involved and are discussed separately:
- right middle lobe collapse
- right lower lobe collapse
- left upper lobe collapse
- left lower lobe collapse
- lingular collapse
Some features, however, are generic markers of volume loss and are helpful in directing ones attention to the collapse, as well as enabling distinction from opacification of the lobe without collapse (e.g. lobar pneumonia). These features include 5:
- elevation of the ipsilateral hemidiaphragm
- crowding of the ipsilateral ribs
- shift of the mediastinum towards the side of atelectasis
- crowding of pulmonary vessels or air bronchograms
Lobar collapse is usually trivially easy to identify on CT, but identification of the cause is not always easy, as the collapsed lung can make identification of an obstructing lesion difficult.