Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: In the retrocardiac space , there is an opacity which was seen in ___ , but it subsequently cleared in ___ . This is worrisome for a pneumonia . Mediastinum again demonstrates stable tortuous aorta with calcified plaque seen at the arch . Cardiac silhouette is stable . No effusions or pneumothoraces are noted . Degenerative changes are seen throughout the spine .
    OUTPUT:
    
Left lower lobe opacity consistent with pneumonia . These findings were discussed with Dr . ___ by Dr . ___ at 11 :57 a .m . via telephone on the day of the study .