Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable semi-upright radiograph of the chest demonstrates persistent retrocardiac patchy opacity , likely atelectasis . There is mild interstitial pulmonary edema , most significant at the bases , which is slightly improved . There are tiny bilateral pleural effusions . The cardiomediastinal and hilar contours are unchanged . There is no pneumothorax .
    OUTPUT:
    
1 . Persistent retrocardiac opacity likely represents atelectasis . 2 . Persistent although somewhat improved mild interstitial pulmonary edema , worst at the bases .