Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The patient is status post coronary artery bypass graft surgery . Allowing for differences in technique , the cardiac , mediastinal and hilar contours appear unchanged . A mild interstitial abnormality appears similar to the prior examination and suggests slight background congestion , but otherwise the lungs appear clear . There are no pleural effusions or pneumothorax . Severe degenerative changes again involve the left shoulder .
    OUTPUT:
    
Mild similar background interstitial abnormality suggesting pulmonary congestion , but similar to before .