Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since the prior chest radiograph performed on ___ , there is increasing left retrocardiac density , likely representing atelectasis . There is likely also atelectasis at the right lung base . Tiny right apical pneumothorax is now appreciated . No pneumothorax on the left . There is likely a small pleural effusion on the right . A small effusion on the left is difficult to exclude . Cardiomediastinal contours are unchanged . Extensive subcutaneous emphysema along both lateral chest walls persists . Mildly displaced left lateral sixth rib fracture demonstrates no evidence of healing .
    OUTPUT:
    
1 . Tiny right apical pneumothorax , without evidence of tension . 2 . Extensive subcutaneous emphysema persists . 3 . Bibasilar atelectasis , slightly increased . 4 . Re-demonstration of mildly displaced left sixth rib fracture , not yet healed .