Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Old healed left - sided rib fractures . There is crowding of the bronchovascular structures at the lung bases relatively increased lucency at the apices consistent with the patient 's known emphysema . Bibasilar atelectasis has improved compared to the prior study . No focal consolidation seen . No pneumothorax seen . Probable small left pleural effusion .
    OUTPUT:
    
Slight improvement in the bibasilar airspace opacities likely reflecting atelectasis . Infection can not be excluded . Persistent small left effusion .