Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is borderline enlarged . The mediastinal and hilar contours are unremarkable . There is no overt pulmonary edema . Hazy opacity within the retrocardiac region could reflect atelectasis but infection or aspiration is not excluded . A small left pleural effusion may be present . There is no pneumothorax .
    OUTPUT:
    
Retrocardiac opacity could reflect atelectasis but infection or aspiration are not excluded . Possible small left pleural effusion .