Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a subtle increase in opacification overlying the left lower lobe in the retrocardiac region which could be secondary to scarring ; however , an acute infectious process can not be excluded . The cardiomediastinal contours are stable . There is no pleural effusion or pneumothorax . Note is made of sternotomy wires which appear to be intact .
    OUTPUT:
    
Subtle increase in opacification overlying the left lower lobe which could be secondary to scarring ; however , an acute infectious process can not be excluded .