Yan Zhou1,2, Hang Xu1, Long Li3,4, Xianghai Ren5,6,7. 1. Department of Pediatric Surgery, Capital Institute of Pediatrics, No. 2 Yabao Road, Chaoyang District, Beijing, 100020, China. 2. Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, 100730, China. 3. Department of Pediatric Surgery, Capital Institute of Pediatrics, No. 2 Yabao Road, Chaoyang District, Beijing, 100020, China. lilong23@126.com. 4. Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, 100730, China. lilong23@126.com. 5. Department of Pediatric Surgery, Capital Institute of Pediatrics, No. 2 Yabao Road, Chaoyang District, Beijing, 100020, China. xianghai_ren@qq.com. 6. Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, 100730, China. xianghai_ren@qq.com. 7. Department of Colorectal and Anal Surgery, Zhongnan Hospital of Wuhan University, Wuhan, 430071, China. xianghai_ren@qq.com.