Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There relatively low lung volumes and bibasilar atelectasis . Left base opacity has improved since the prior study and most likely represents atelectasis although infectious process is not entirely excluded in the appropriate clinical setting . No large pleural effusion is seen . There is no pneumothorax . Cardiac and mediastinal silhouettes are stable .
    OUTPUT:
    
Left base atelectasis , improved since the prior study ; underlying infectious process not entirely excluded in the appropriate clinical setting . .