Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal silhouette and pulmonary vasculature are unremarkable . The lungs are mildly hyperexpanded , consistent with COPD . No definite consolidation is identified . There is no pleural effusion or pneumothorax . Again noted is a retrocardiac opacity , not changed since prior examination , which may represent a hiatal hernia .
    OUTPUT:
    
1 . COPD . 2 . Stable retrocardiac density which may represent a hiatal hernia .