Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A portable frontal chest radiograph demonstrates interval increase in a previously seen left pleural effusion , now large with only a small amount of aerated lung in the left lung apex . This appears to exert mass effect upon the mediastinum , which is now shifted to the right . The right lung appears normally aerated without focal consolidation , pleural effusion , or pneumothorax . There is no appreciable left - sided pneumothorax . The visualized upper abdomen is unremarkable .
    OUTPUT:
    
Large left pleural effusion exerting mass effect upon the mediastinum , which is now shifted to the right .