Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since the prior CXR on ___ , the lungs are better aerated . The small to moderate left effusion appears better , but this may be partially due to erect positioning . There is still significant retrocardiac atelectasis . No new areas of consolidation . Right lung is essentially clear . No pneumothorax . Stable cardiomediastinal silhouette .
    OUTPUT:
    
Slight interval improvement in left effusion , though this may be partially due to positioning .