Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are normally expanded . Faint opacity at the left base is similar to the study of ___ . There is no convincing evidence of pneumonia . There is no pleural effusion or pneumothorax . The cardiomediastinal silhouette hilar contours are normal . CBD stents are incidentally seen in the right upper quadrant .
    OUTPUT:
    
Persistent left lower lobe opacity is unchanged since ___ and may reflect atelectasis . There is no convincing evidence of pneumonia .