IMPRESSION:
AP chest compared to :
 
 Left lower lobe collapse is new.  Poor definition of the bronchial tree below
 the left main bronchus suggest retained secretions, but mass could be present.
 Small accompanying left pleural effusion is common with lower lobe collapse. 
 Right lung clear.  At least one right lung nodule is present.  Heart size
 indeterminate, was moderately enlarged prior to left lung collapse.