Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy . A right lower lobe opacity reflects a fat containing Bochdalek 's hernia as seen on the reference chest CT . There are bibasilar opacities , possibly reflecting atelectasis . No pleural effusion or overt pulmonary edema is noted . The heart is normal in size , and the thoracic aorta is enlarged as noted on the prior chest CT .
    OUTPUT:
    
Bibasilar opacities likely reflect atelectasis . No pulmonary effusion .