 2. Safety of CME CME group and non-CME group were compared the differences of security, included operation time, blood loss, postoperation complications, flatus restoring time, defecation restoring time, drainage removal time, Diet restoring time, drainage volume in three days after surgery, hospital deaths, the exhaust time, hospitalization time and hospitalization costs. In addition, the feasibility of CME techniques as the surgical approach of choice for elderly patients was also evaluated. 