Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . Increased retrocardiac opacity compared to the prior exam may reflect normal bronchovascular crowding and atelectasis in the setting of low lung volumes ; however , infection appropriate clinical situation can not be excluded . Left lower lung atelectasis has increased in the interim . No large pleural effusion . The heart size is moderately enlarged , probably similar to the prior exam when accounting for lower lung volumes . The mediastinum is not widened . No pneumothorax . No acute osseous abnormality
    OUTPUT:
    
Low lung volumes with retrocardiac opacity likely atelectasis but to be correlated clinically .