Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac silhouette is significantly enlarged . A retrocardiac opacity likely relates to a combination of pleural effusion and volume loss , as seen on prior chest CT examination . Increased opacity at the right lung base is also likely due to a combination of pleural fluid and atelectasis . However , an underlying infectious process can not be excluded . There is no pneumothorax . Bilateral shoulder prostheses are noted .
    OUTPUT:
    
Bibasilar opacities are likely a combination of pleural effusion and atelectasis , however an underlying infectious process can not be excluded .