Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Dense left retrocardiac opacity most likely represents atelectasis , but pneumonia could be considered in the appropriate clinical setting . Background interstitial pulmonary edema is mild . Bilateral pleural effusions , small on the right , and trace on the left . No pneumothorax . Heart size is moderately enlarged . Note is made of a prostatic mitral valve . Aortic arch calcifications are noted . The median sternotomy wires are intact . No acute osseous abnormalities identified . No subdiaphragmatic free air .
    OUTPUT:
    
1 . Left retrocardiac opacity most likely represents atelectasis , although pneumonia could be considered in the appropriate clinical setting . 2 . Mild interstitial pulmonary edema . 3 . Bilateral pleural effusions , small on the right , and trace on the left .