Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Stable retrocardiac opacity is most consistent with atelectasis . The lungs are otherwise clear . There is a stable trace left pleural effusion . No right pleural effusion . No pneumothorax . Heart size , mediastinal contour , and hila are unremarkable . Limited assessment of the upper abdomen is unremarkable . Visualized osseous structures are notable for left clavicle fixation hardware .
    OUTPUT:
    
1 . Stable retrocardiac opacity is most consistent atelectasis . 2 . Stable trace left pleural effusion . 3 . No pneumothorax .