Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is chronic cardiomegaly with a dual lead pacemaker , mediastinal surgical clips , and artificial aortic valve . There is a retrocardiac opacity . There is chronic elevation of the right hemidiaphragm with normal colonic gas projecting under the right hemidiaphragm . There is no pneumothorax . There is no large pleural effusion . Pulmonary vascularity is normal . No clavicular fracture is noted .
    OUTPUT:
    
Retrocardiac opacity may represent atelectasis but pneumonia can not be excluded in the appropriate clinical context .