Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patchy left lower lobe opacity could be due to atelectasis or less likely subtle / very early pneumonia . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Subtle left lower lobe opacity more likely due to atelectasis versus less likely subtle / very early pneumonia .