Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since prior , there has been a slight improvement of a left pleural effusion . Opacification of the left mid lung persists and likely represents rounded atelectasis . The right lung is grossly clear without a right pleural effusion . There is no pneumothorax . Cardiomediastinal silhouette is unchanged .
    OUTPUT:
    
Slight decrease in size of left pleural effusion .