Massive pleural effusion

Massive pleural effusion. In this example, there is complete ‘white-out’ of the right hemithorax. A big clue to the cause here is the fact that the trachea is being pushed to the opposite side. In this setting, a massive pleural effusion is the most likely cause, although a huge lung mass could also potentially have this appearance. If the trachea were being pulled towards the opacified side, the differential diagnosis changes to pneumonectomy or complete collapse of the lung, which could be caused by an obstructing tumour in the right main bronchus.