Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size remains mild to moderately enlarged . The mediastinal and hilar contours are unchanged with a small hiatal hernia again noted . There is mild pulmonary vascular congestion . There are small bilateral pleural effusions , not changed from the prior study . Retrocardiac patchy opacity may reflect atelectasis though infection is difficult to exclude . Hypertrophic changes are again noted within the thoracic spine . No subdiaphragmatic free air is identified .
    OUTPUT:
    
Mild pulmonary vascular congestion and small bilateral pleural effusions . Retrocardiac atelectasis , though infection can not be completely excluded .