Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and aortic valve replacement . Previously noted right internal jugular central venous catheter has been removed . There is mild enlargement of the cardiac silhouette which is unchanged . Aortic knob is calcified . There are low lung volumes . There is crowding of the bronchovascular structures but no overt pulmonary edema . Retrocardiac opacity persists , and a small left pleural effusion likely remains . There is no pneumothorax . No acute osseous abnormality is seen .
    OUTPUT:
    
Persistent retrocardiac opacity likely reflecting atelectasis though infection can not be excluded . Small left pleural effusion , relatively unchanged . Crowding of the bronchovascular structures without overt pulmonary edema .