Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Retrocardiac opacity is seen which likely represents volume loss left lower lobe however pneumonia can not be excluded . A lateral view would be helpful in localizing the opacity . Also seen is a small opacity at the base of the right lung which partially obscures the right hemidiaphragm . The cardiomediastinal silhouette and hilar contours are unchanged . The pleural surfaces are normal without effusion or pneumothorax .
    OUTPUT:
    
Retrocardiac opacity likely represents volume loss left lower lobe however pneumonia can not be excluded .