Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post median sternotomy and CABG . Cardiac silhouette size is borderline enlarged . The aortic knob is calcified . Mediastinal and hilar contours are within normal limits . Pulmonary vasculature is not engorged . Patchy opacity in the retrocardiac region is demonstrated . No pleural effusion or pneumothorax is present . No acute osseous abnormality is detected .
    OUTPUT:
    
Retrocardiac opacity concerning for pneumonia . RECOMMENDATION ( S ) : Followup radiographs after treatment are recommended to ensure resolution of this finding .