Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There are low lung volumes . There is persistent left pleural effusion which appears small to moderate but slightly decreased as compared to the prior study . Left base retrocardiac opacity is most likely due to combination of pleural effusion and atelectasis . The right lung is grossly clear . Cardiac and mediastinal silhouettes are grossly stable .
    OUTPUT:
    
Left pleural effusion which may be slightly improved . Possible very trace right pleural effusion .