Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is mildly enlarged . The patient is status post coronary artery bypass graft surgery . The aortic arch is calcified . There is again an expansile soft tissue opacity along the lower mediastinum immediately above the thoracic inlet . Mild to moderate relative elevation of the right hemidiaphragm compared to the left is noted . There is no evidence for pleural effusion or pneumothorax . The lungs appear clear . The bones are probably demineralized to some degree .
    OUTPUT:
    
1 . No evidence of acute disease including no evidence for pleural effusion . 2 . Soft tissue density in the lower mediastinum suspected to represent a hiatal hernia but not entirely characterized ; it is difficult to exclude an aneurysm . If more remote prior radiographs are not available to show stability of this appearance , then characterization should be considered with chest CT when clinically appropriate .