Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Low lung volumes are low . This accentuates the size of the cardiac silhouette which is top normal . Mediastinal contour is unchanged . There is crowding of the bronchovascular structures . No overt pulmonary edema is demonstrated . The hila are unremarkable . Patchy opacities in the lung bases likely reflect atelectasis though infection or aspiration can not be excluded , particularly within the left lung base . A trace left pleural effusion may be present . No pneumothorax is identified . Multilevel degenerative changes are noted in the thoracic spine .
    OUTPUT:
    
Bibasilar airspace opacities , more pronounced on the left , which may reflect atelectasis but infection or aspiration can not be excluded . Possible trace left pleural effusion . Low lung volumes .