Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a new left lung base opacity , obscuring the hemidiaphragm posteriorly . A spiration or pneumonia can not be excluded in the appropriate clinical setting . The right lung is essentially clear . No pneumothorax . Cardiomediastinal silhouette is within normal limits . No acute osseous abnormalities . An enteric tube terminates in the stomach .
    OUTPUT:
    
New left lung base opacity , which could be due to a small pleural effusion with adjacent atelectasis or to pnemonia / aspiration pneumonia .