Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal contours are within normal limits and without change . Areas of linear atelectasis are present at both lung bases . Additional slightly more confluent opacity overlies the lower thoracic spine corresponding to the right retrocardiac region on the PA view . No pleural effusion or pneumothorax .
    OUTPUT:
    
Bibasilar linear atelectasis . Additional patchy opacity in right lower lobe posteriorly may represent atelectasis or pneumonia .