Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a very large right - sided pleural effusion including leftward shift of mediastinal structures to a mild - to - moderate degree . There is also probably extensive associated right lung atelectasis . The left lung appears clear without pleural effusion . There is no pneumothorax . Bony structures are unremarkable .
    OUTPUT:
    
Large right - sided pleural effusion .