Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart may be mildly enlarged on this AP projection . The mediastinal and hilar contours are within normal limits . There is a subtle retrocardiac opacity , seen better on the lateral view . There is no pleural effusion or pneumothorax identified .
    OUTPUT:
    
Subtle retrocardiac opacity , better appreciated on the lateral view may represent infection in the appropriate clinical setting .