Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiomediastinal and hilar contours are within normal limits . A very subtle opacity the base of the left lung appears less conspicuous on the current examination and may reflect a resolving focus of infection . No pleural effusion or pneumothorax .
    OUTPUT:
    
Very subtle opacity seen at the left base on the frontal view appears less conspicuous on the current exam and may reflect an area of persistent or resolving infection in the appropriate clinical setting .