Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy and CABG . The cardiac , mediastinal and hilar contours are unchanged , with the heart size within normal limits . Calcification of the aortic arch is redemonstrated . The pulmonary vascularity is normal . Again demonstrated is a retrocardiac opacity , which again may represent atelectasis or aspiration . The right lung is grossly clear . No pneumothorax is seen . There is likely a small left pleural effusion . Mild degenerative changes in the thoracic spine are redemonstrated .
    OUTPUT:
    
Persistent retrocardiac consolidative opacity which may reflect atelectasis and / or aspiration . Small left pleural effusion .