Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac , mediastinal and hilar contours appear within normal limits . A plate - like opacity in the left lower lobe is probably due to atelectasis although not entirely specific . There is no pleural effusion or pneumothorax . Otherwise , the lungs appear clear .
    OUTPUT:
    
Opacity at the lung left lung base , not entirely specific although probably compatible with atelectasis .