Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy and CABG . Subtle left base retrocardiac opacity may be due to atelectasis and vascular structures although an early consolidation due to infection or aspiration is not excluded in the appropriate clinical setting . No pleural effusion or pneumothorax is seen . The cardiac and mediastinal silhouettes are stable .
    OUTPUT:
    
Subtle left base retrocardiac opacity may be due to atelectasis and vascular structures although an early consolidation due to infection or aspiration is not excluded in the appropriate clinical setting . Otherwise , no significant interval change .