Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to the prior radiograph , there has been improvement in lung volumes and there is a persistent small left pleural effusion . Retrocardiac opacity likely represents atelectasis . Heart size is enlarged but stable . No evidence of pneumonia .
    OUTPUT:
    
Small left pleural effusion and mild cardiomegaly . No evidence of pneumonia .