Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since the most recent chest radiograph from ___ , there is persistent opacification of the left lung base , compatible with pneumonia . This is not significantly changed . The remainder of the lungs are clear . Trace left pleural effusion is also stable . No pneumothorax . Cardiomediastinal contours are unchanged .
    OUTPUT:
    
Unchanged left lower lobe pneumonia . No significant change since ___ .