Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is normal . Hilar and mediastinal contours are normal . There is a subtle increase in opacification at the right lung base . There is no pleural effusion or pneumothorax . The visualized osseous structures are unremarkable .
    OUTPUT:
    
Subtle increase in opacity at the right lung base may be secondary to atelectasis , however an acute infectious process can not be excluded .