Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a moderate - to - large left - sided pleural effusion , new since the prior study . There is no shift of mediastinal structures . Probably , there is substantial associated atelectasis involving the left lower lobe and possibly parts of the lingula . The pulmonary vasculature is mildly prominent . There is no pleural effusion on the right . No pneumothorax is identified .
    OUTPUT:
    
Moderate - to - large left - sided pleural effusion . Findings suggesting mild vascular congestion .