Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lung volumes are slightly low . There are patchy opacities in the lung bases , similar to the prior study likely reflecting areas of atelectasis . The cardiac , mediastinal and hilar contours are unchanged . There is no pneumothorax or pleural effusion . There are multilevel degenerative changes in the thoracic spine .
    OUTPUT:
    
Patchy opacities at lung bases likely reflect atelectasis in the setting of low lung volumes .