Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single portable semi-upright chest radiograph demonstrates unremarkable mediastinal and hilar contours . Heart size is top normal . Lungs are clear . No pleural effusion or pneumothorax evident . No osseous abnormality is identified .
    OUTPUT:
    
Clear lungs . Appearance of mildly enlarged heart may be due to patient position , recommend re-evaluation with upright conventional radiographs when patient is stable .