Department of General Surgery, Beijing Hospital, National Geriatrics Center, Beijing, China. zhumw2013@163.com. Department of General Surgery, Beijing Hospital, National Geriatrics Center, Beijing, China. Department of General Surgery, Peking University Third Hospital, Beijing, China. Department of General Surgery, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China. Department of General Surgery, Nanfang Hospital Affiliated to Southern Medicine University, Guangzhou, China. Department of General Surgery, Ruijin Hospital Shanghai Jiaotong University School of Medicine, Shanghai, China. Department of Gastrointestinal Surgery, Shanghai Sixth Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China.