Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared with the prior studies , the known left sided loculated pleural effusion is similar in appearance . However a retrocardiac opacity is again seen , for which infection is not excluded . Cardiomediastinal and hilar silhouettes are unchanged . The tracheostomy tube is also unchanged . Median sternotomy wires are intact . Hardware overlying the sternum is also unchanged . The pigtail catheter overlying the left upper abdominal quadrant is again noted .
    OUTPUT:
    
1 . Retrocardiac opacity is similar in appearance to the studies of ___ , but overlying infection is not excluded . 2 . Small left loculated effusion is unchanged in appearance .