Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to the prior radiograph , there is increased opacification in the retrocardiac region , which could represent atelectasis or developing infection . The lungs are otherwise clear . Cardiomediastinal silhouette is normal . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Increased retrocardiac opacification could represent atelectasis or developing infection .