There is complete white-out of the right hemithorax. What conditions can cause complete white-out of a hemithorax?
Consolidation, atelectasis and complete collapse of the lung, pleural effusion/collection.
Are there features in this case that make one differential more likely than the other?
There is no volume loss, so a diagnosis of complete lung collapse seems unlikely. If this were complete consolidation of the right lung, one would expect rather more in the way of air-bronchograms. This case represents a huge pleural effusion.
Now we know this is an effusion, what are the potential causes?
The differential for causes of a pleural effusion is huge, but the unilaterality and size of the effusion make malignancy by far the most likely diagnosis.
Frontal and lateral radiographs of the chest demonstrate complete white out of the right hemithorax. There is evidence of positive mass effect upon the mediastinum which is shifted towards the left (including the trachea), with leftward bowing of the azygo-oesophageal recess. The right ribs are also splayed.
On lateral projection only one pleural cavity is visible (the left one).