[1] Shenyang Anorectal Hosp, Dept Gen Surg, 9 Nanjingbei St, Shenyang 110054, Liaoning, Peoples R China
[2] Dalian Med Univ, Dept Gen Surg, Hosp 2, Dalian 116000, Liaoning, Peoples R China
[3] Daqing Oilfield Gen Hosp, Dept Gen Surg, Daqing 163000, Heilongjiang, Peoples R China