Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: One portable upright view of the chest . Again seen are bibasilar opacities , some of which likely represent atelectasis and scarring given patient 's history of chronic aspiration . However , underlying pneumonia in lower lobes can not be ruled out , particularly on the right where the opacity has progressed . Cardiac , mediastinal , and hilar contours are unremarkable . The upper lung zones appear clear . No pneumothorax and no pleural effusion .
    OUTPUT:
    
Bibasilar opacities likely represent combination of atelectasis and scarring given patient 's history of chronic aspiration . However , underlying pneumonia in the lower lobes particularly on the right can not be ruled out .