Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and CABG . Heart size is mildly enlarged , unchanged . Mediastinal and hilar contours are unremarkable . Pulmonary vasculature is normal . Linear opacity in the left lower lobe may reflect subsegmental atelectasis or scarring . Remainder of the lungs are clear . No focal consolidation or pneumothorax is present . Blunting of the left costophrenic angle on the lateral view suggests a trace pleural effusion . No acute osseous abnormality is visualized .
    OUTPUT:
    
Subsegmental atelectasis versus scarring in the left lower lobe . Trace left pleural effusion .