Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Subtle left basilar opacity likely corresponds to atelectasis / possible pulmonary contusion as seen on CT earlier today . No large pleural effusion is seen . There are no findings to suggest pneumothorax . There are multiple left - sided rib fractures , better assessed on CT , however , 1 reasonably well seen involves the posterior left 4th rib is , which is minimally displaced . The cardiac and mediastinal silhouettes are unremarkable .
    OUTPUT:
    
Multiple left - sided rib fractures , better assessed on CT . Subtle possibly left lung base opacity likely relates to atelectasis / pulmonary contusion as seen on CT .