Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low leading to crowding of the bronchovascular structures . Interval increased airspace opacity at the left lung base may represent atelectasis versus pneumonia . No large pleural effusion or pneumothorax . Tortuosity of the thoracic aorta and a dilated pulmonary conus are again noted .
    OUTPUT:
    
Low lung volumes with left lower lobe airspace opacity may represent atelectasis , although superimposed infection is difficult to exclude . The patient has a history of pulmonary embolism , if this is suspected clinically , a chest CT angio may be obtained for further evaluation .