Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and CABG . Heart size remains mildly enlarged , unchanged . Moderate size hiatal hernia is re - demonstrated . Aortic knob calcifications are present . The mediastinal and hilar contours are unchanged , and there is no pulmonary vascular congestion . Linear opacities in both lung bases likely reflect subsegmental atelectasis . Minimal blunting of the left costophrenic sulcus suggests a trace left pleural effusion . No pneumothorax is identified .
    OUTPUT:
    
Mild bibasilar atelectasis and probable trace left pleural effusion . Unchanged moderate size hiatal hernia .