Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Pacer wires are unchanged in position , ending in the right ventricle and right atrium . The cardiomediastinal silhouette is normal . There is no pneumothorax or pleural effusion . There is subtle opacity in the left perihilar region , increased from prior .
    OUTPUT:
    
Subtle opacity in the left perihilar region , concerning for developing pneumonia , likely within the superior segment of the left lower lobe .