Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac and mediastinal silhouettes are stable . There is slight increase in left base patchy opacity , and underlying infection or aspiration is not excluded . There is an old fracture of the posterolateral left sixth rib with additional prior left - sided rib fractures difficult to exclude . No overt pulmonary edema is seen . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Subtle left base opacity could be due to infectious process .