Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided small to moderate hydropneumothorax has slightly decreased when compared to the prior examination . A new left - sided pleural drain is seen . The left - sided pleural fluid has also decreased . There is persistent retrocardiac opacity . The appearance of the right lung is unchanged with numerous pulmonary not . There is a prominent likely skin fold . Mild mediastinal shift to the left .
    OUTPUT:
    
Slight interval decrease in the left - sided hydro pneumothorax post pleural drain catheter insertion .