Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are slightly low with bibasilar atelectasis or scarring similar to prior studies . There is no evidence of new focal airspace opacity to suggest pneumonia . Heart size is top normal . The mediastinal hilar contours is stable . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Stable atelectasis or scarring at the lung bases . No evidence of pneumonia .