Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The mediastinal and hilar contours are normal . The pulmonary vasculature is normal . There is subtly increased opacity involving the left upper lobe which could represent infection in the appropriate clinical setting . . No pleural effusion or pneumothorax is seen .
    OUTPUT:
    
Subtly increased opacity involving the left upper lobe which could represent an area of infection in the appropriate clinical setting .