Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is no pneumothorax . The cardiac , mediastinal and hilar contours appear unchanged . Left basilar opacities persist , but perhaps minimally improved . A Trace pleural effusion may be new on the right . It is difficult to exclude a very small pleural effusion on the left .
    OUTPUT:
    
No evidence of pneumothorax .