Large isolated right upper lobe bulla.  The left lung is entirely normal in appearance.

In the acute setting for the unprepared, this may be mistaken for a pneumothorax and lead to pleural drain insertion.  

Two ways at least to avoid this mistake:

1.  Take a look for old films.  It might sound boring and repetitive, but it is so helpful, so often.

2.  In this case, the increased bronchovascular markings in the lower zone are the normal lobes compressed.  In a pneumothorax of this size the lung normal collapses towards the hilum.

This kind of bullous disease would be a candidate for bullectomy.