Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are within normal limits . The trachea is central . Even allowing for the projection , the heart is mildly enlarged . Left lower lobe atelectasis , can not exclude superimposed infection . No pleural effusions seen . No pneumothorax .
    OUTPUT:
    
Left lower lobe atelectasis , can not exclude superimposed infection .