Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There are relatively low lung volumes , which accentuate the bronchovascular markings . However , given this , patchy left basilar opacity is seen and an infectious process is not excluded . There is mild elevation of the anterior right hemidiaphragm . Retrocardiac density , best seen on the lateral view , also seen on the prior study , may be due to a hiatal hernia . No large pleural effusion or pneumothorax is seen . The cardiac silhouette is top normal to mildly enlarged . The mediastinal contours are unremarkable .
    OUTPUT:
    
Low lung volumes which accentuate the bronchovascular markings . Patchy opacity projecting over the lateral left lung base on the frontal view , not well substantiated on the lateral view , may be due to atelectasis versus infection .