Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since prior , there is new retrocardiac opacity which silhouettes the hemidiaphragm . Streaky right basilar opacity is unchanged , potentially atelectasis . Superiorly the lungs are clear . Cardiac silhouette is enlarged but stable . No acute osseous abnormalities .
    OUTPUT:
    
Interval development of a left basilar opacity which could be due to atelectasis though infection or aspiration are possible .