Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since prior , there has been little change to a large left pleural effusion which continues to occupy approximately ___ of the left hemithorax . The right lung is clear . There is no right pleural effusion . Left heart border is obscured by fluid , the right heart border is unchanged .
    OUTPUT:
    
Large left pleural effusion occupying approximately ___ of the left hemithorax .