Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: As compared to the prior examination , there has been interval removal of a right internal jugular central venous line . A left IJ hemodialysis catheter is unchanged in position . There is a new retrocardiac , left lower lobe opacity obscuring the left hemidiaphragm . A left small pleural effusion is stable . The patient is status post sternotomy , and the cardiomediastinal silhouette is stable .
    OUTPUT:
    
New , left retrocardiac opacity may reflect atelectasis or pneumonia , in the appropriate clinical setting .