Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable semi-upright radiograph of the chest demonstrates hyperexpanded lungs . Mild diffuse interstitial abnormality is of uncertain chronicity . The cardiomediastinal and hilar contours are unremarkable . The patient is status post median sternotomy . There is no pneumothorax , pleural effusion , or consolidation .
    OUTPUT:
    
Mild diffuse interstitial abnormality is of uncertain chronicity .