Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is vague opacity in the left lung base which is stable from prior exam and likely represents scarring . There are no convincing signs of pneumonia or CHF . No large effusion or pneumothorax is seen . The cardiomediastinal silhouette is normal . The imaged bony structures are intact . There is no free air below the right hemidiaphragm .
    OUTPUT:
    
Left basal opacity with slight elevation of the left hemidiaphragm , stable , likely represents scarring . Please refer to subsequent CTA chest for further details .