Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is increased opacity projecting over the lung bases particularly on the lateral view in the retrocardiac region . Based on the frontal there is more retrocardiac opacity than right basilar opacity . Superiorly , the lungs are clear . The cardiac silhouette is within normal limits . Chronic left lateral fourth and fifth rib fractures are noted , in part creating opacity projecting over left upper lung laterally . No acute osseous abnormalities .
    OUTPUT:
    
Basilar opacities , left greater than right which could represent either atelectasis versus infection or aspiration . .