Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A Port - A - Cath terminates in the superior vena cava . The cardiac , mediastinal and hilar contours appear stable . There is vague persistent opacity in the left lower lobe which is apparently a background finding , likely due to atelectasis . Otherwise the lungs appear clear . There are no pleural effusions or pneumothorax . There is no free air .
    OUTPUT:
    
Persistent vague left base opacity , probably atelectasis .