Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There are low lung volumes . The heart size remains mildly enlarged . The mediastinal and hilar contours are stable . There is crowding of the bronchovascular structures , without overt pulmonary edema . More focal opacification in the left lower lobe could reflect an area of atelectasis , though infection or aspiration can not be completely excluded . There is no pneumothorax or pleural effusion . No acute osseous abnormality is seen .
    OUTPUT:
    
Low lung volumes . More focal opacity in the left lung base may reflect an area of atelectasis , though infection or aspiration can not be completely excluded .