Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A large , multiloculated left pleural effusion and substantial atelectasis at the left lung base are mildly improved from the prior exam . A pigtail catheter is seen projecting over the left hemithorax . The right lung is clear . The heart is enlarged and grossly unchanged . There is no evidence of pneumothorax .
    OUTPUT:
    
Large , left multiloculated pleural effusion minimally improved from the prior study .