Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is normal in size . The mediastinal and hilar contours appear within normal limits . There is no pleural effusion or pneumothorax . The lateral view suggests a patchy posterior infrahilar opacity which is highly non-specific and not well demonstrated on the frontal view , although probably retrocardiac .
    OUTPUT:
    
Patchy posterior lung opacity , highly non-specific , most likely , retrocardiac . Differential considerations include a variety of etiologies including atelectasis .