Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal silhouette is normal . There is no pleural effusion or pneumothorax . There is a subtle opacity posteriorly on lateral view which likely corresponds to increased lung markings in the left lower lobe . There is no acute osseous abnormality .
    OUTPUT:
    
Subtle increased retrocardiac opacity which could represent an early pneumonia in the correct clinical setting .