Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a retrocardiac opacity with air bronchograms concerning for infection . The cardiac silhouette is moderately enlarged but unchanged . There is no pleural effusion or pneumothorax . Surgical clips are noted in the region of the thyroid gland . Included upper abdomen is unremarkable . Osseous structures are grossly intact .
    OUTPUT:
    
Left lower lobe pneumonia .