Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy and CABG . The cardiac silhouette is top - normal to mildly enlarged . The right lung is grossly clear . Subtle left base retrocardiac opacity may be due to atelectasis versus pneumonia . Dedicated PA and lateral views may be helpful for further evaluation . No large pleural effusion is seen . There is no pulmonary edema .
    OUTPUT:
    
Left base retrocardiac opacity may be due to atelectasis versus pneumonia . Dedicated PA and lateral views would be helpful for further evaluation .