Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to the prior examination , there is new opacification of the left lower lobe , which likely represents atelectasis , however an underlying pneumonia can not be excluded . There is a probable small left pleural effusion . The lungs are otherwise clear . The pulmonary vasculature is normal . There is stable enlargement of the cardiomediastinal silhouette with significant tortuosity of the descending aorta . No pneumothorax is visualized .
    OUTPUT:
    
1 . New left lower lobe opacification , which likely represents atelectasis , however an underlying pneumonia can not be excluded . 2 . Small left pleural effusion .