CXR | Notion

There are numerous causes of white shadowing in the lungs including:

consolidation
pleural effusion
collapse
pneumonectomy
specific lesions e.g. tumours
fluid e.g. pulmonary oedema

If there is a 'white-out' of a hemithorax it is useful to assess the position of the trachea - is it central, pulled or pushed from the side of opacification.

Trachea pulled toward the white-out	Trachea central	Trachea pushed away from the white-out
Pneumonectomy	Consolidation	Pleural effusion
Complete lung collapse e.g. endobronchial intubation	Pulmonary oedema (usually bilateral)	Diaphragmatic hernia
Pulmonary hypoplasia	Mesothelioma	Large thoracic mass

Lung collapse - note how the trachea is pulled towards the side of the white-out

Pleural effusion - note how the trachea (blue) is pushed away the side of the white-out. The other signs of a positive mass effect include leftward bowing of the azygo-oesophageal recess (yellow) and splaying of the ribs on the right (red)

For more information check out the link to the superb Radiology Masterclass website.