Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post coronary artery bypass graft surgery . The cardiac , mediastinal and hilar contours appear unchanged . Allowing for low lung volumes , patchy left basilar opacities appear unchanged and suggest mild chronic scarring . There is similar slight relative elevation of the left hemidiaphragm . There is no pleural effusion or pneumothorax . Bony structures are unremarkable .
    OUTPUT:
    
No evidence of acute disease .