Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP chest radiograph ___ at 18 :45 is submitted .
    OUTPUT:
    
The patient is status post median sternotomy . The nasogastric tube has been removed . Overall cardiac and mediastinal contours are stable . Interval appearance of opacity in the retrocardiac region which may reflect early pneumonia or aspiration , although atelectasis could also have this appearance . Clinical correlation is advised . No pulmonary edema . No pneumothorax .