Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Subtle left mid lung opacity persists which could be due to a small focus of pneumonia . Patchy left base retrocardiac opacity likely represents atelectasis . No evidence of pneumonia is seen on the right . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are stable .
    OUTPUT:
    
Subtle left mid lung opacity persists which could be due to small focus of pneumonia versus artifact .