Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable chest radiograph demonstrates unremarkable hilar and cardiac contours . Patient has a tortuous aorta . Interval widening of the mediastinum compared to ___ , though this is likely exaggerated by patient positioning and bilateral low lung volumes . Lungs are clear . No large pleural effusion or pneumothorax is seen . Patient is status post sternotomy .
    OUTPUT:
    
Apparent minimal interval widening of mediastinum likely exaggerated by patient positioning and low lung volumes though can not exclude aneurysmal dilatation which could be further evaluated for on chest CTA .