Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . This accentuates the size of the cardiac silhouette which is mildly enlarged . Aortic knob is calcified . Apparent superior mediastinal widening is likely due to low lung volumes . Crowding of the bronchovascular structures is noted with mild pulmonary vascular congestion . Patchy bibasilar airspace opacities , more pronounced in the retrocardiac region could reflect atelectasis but infection is not excluded . No pleural effusion or pneumothorax is seen . No acute osseous abnormality is identified .
    OUTPUT:
    
Low lung volumes . Mild pulmonary vascular congestion and bibasilar opacities , possibly reflecting atelectasis but infection can not be excluded . Overall , these findings are not significantly changed compared to the previous exam .