Intestinal fistula after intestinal cancer surgery is mainly caused by the anastomosis not completely healed. There are many reasons for this, such as the suturing technique is not good enough, for example, when the suture or the anastomosis of the intestinal canal is closed, resulting in local ischemia, or when the suture is not tight enough, resulting in local leakage, so the patient has intestinal fistula after surgery. In addition, it may be caused by bleeding from the anastomosis, because after the anastomosis bleeds, it will lead to local ischemia, and later intestinal fistula may appear. In addition, if the patient is older and has poor nutritional status, such as hypoproteinemia, the anastomosis may heal poorly during the healing process, so that an intestinal fistula may also occur. In addition, if the patient has a low rectal tumor and undergoes anus-preserving surgery, many patients will also develop intestinal fistula due to poor local blood supply.