Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright and lateral views of the chest provided . There is increased retrocardiac opacity which could reflect the presence of a left lower lobe pneumonia . Linear densities in the left and right mid lung are unchanged likely scarring . No large effusion or pneumothorax . No signs of congestion or edema . Cardiomediastinal silhouette is stable . Bony structures appear intact .
    OUTPUT:
    
Retrocardiac opacity concerning for left lower lobe pneumonia .