Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is bibasal atelectasis and crowding of the bronchovascular structures due to low lung volumes . With this in mind , there is no definitive evidence of pneumonia . A retrocardiac opacity appears to be stable since the ___ study , likely representing atelectasis rather than pneumonia . No acute appearing fractures are identified . Cardiac silhouette remains stable in size .
    OUTPUT:
    
Bibasal atelectasis without definitive evidence of pneumonia .