Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low leading to crowding of the bronchovascular structures . Mild bibasilar and left retrocardiac airspace opacities likely reflect atelectasis . There is no lobar consolidation , pleural effusion , pneumothorax , or pulmonary edema . The cardiac silhouette is normal in size . No acute displaced rib fractures are identified .
    OUTPUT:
    
Low lung volumes and bibasilar airspace opacities which likely reflect atelectasis , although superimposed infection is difficult to exclude .