Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac , mediastinal and hilar contours appear stable . There is a new nonspecific retrocardiac opacity obscuring the left hemidiaphragmatic border . Coinciding pleural effusion is not excluded on the left . There is probably a very small pleural effusion on the right . There are also mild congestive changes .
    OUTPUT:
    
New retrocardiac opacification , a typical site for atelectasis although pneumonia is not excluded . Findings suggest mild vascular congestion .