Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well - expanded . There has been interval significant decrease in the left pleural effusion . Retrocardiac opacity remains , likely representing atelectasis . The remainder of the left lung and the entire right lung are clear . There is no left pleural effusion . There is no pneumothorax . The cardiomediastinal silhouette is top - normal in size .
    OUTPUT:
    
1 . Interval significant decrease in left pleural effusion . 2 . Retrocardiac opacity , likely reflecting atelectasis .