Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac , mediastinal and hilar contours appear stable . Patchy retrocardiac opacity appears streaky and probably due to atelectasis . Otherwise the lungs appear clear . There are no pleural effusions or pneumothorax .
    OUTPUT:
    
Mild retrocardiac opacification , most commonly due to atelectasis also although not entirely specific .