Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal contours are within normal limits in this patient status post previous median sternotomy and coronary bypass surgery . Lung volumes are low . Bibasilar subsegmental atelectasis is present as well as a possible small left pleural effusion with adjacent mild elevation left hemidiaphragm . No focal areas of consolidation are evident . Small - caliber vascular catheter terminates at cavoatrial junction .
    OUTPUT:
    
No radiographic evidence of pneumonia .