Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Right sided dual - chamber pacemaker device is re - demonstrated with leads in the right atrium and right ventricle . Lung volumes are low . Heart size is mildly enlarged . Widening of the superior mediastinal contour is likely due to low lung volumes . Crowding of bronchovascular structures is present without overt pulmonary edema . Bibasilar airspace opacities may reflect atelectasis , however infection or aspiration can not be excluded . No large pleural effusion or pneumothorax is present . Large hiatal hernia is re - demonstrated .
    OUTPUT:
    
Low lung volumes with bibasilar airspace opacities , possibly atelectasis , but infection or aspiration can not be excluded . Large hiatal hernia .