The causes of swelling and pain in the wound on the thirteenth day of hemorrhoid surgery include normal postoperative reaction, incomplete wound healing, and wound infection. 1. Post-operative reaction: patients in hemorrhoid surgery after the swelling pain, especially after internal hemorrhoid surgery, may be a normal post-operative reaction, this is due to the hemorrhoid nucleus in the area above the dentate line, there are nerves innervating the internal organs, in the process of surgery, ligation of hemorrhoids, may involve the nerve, which triggered the symptoms of post-operative swelling pain. 2. Wound healing incomplete: due to hemorrhoid surgery, there will be a scar, if the wound is not completely healed 13 days after the operation, when the patient activities, hard to defecate, etc., will pull the wound, resulting in patients with symptoms of swelling and pain. 3. Wound infection: after surgery, before the wound is completely healed, patients still have to defecate normally, and feces contains a lot of food residue or harmful substances, etc., which is easy to cause the wound to be invaded by bacteria, the local wound infection occurs, which triggers the patient to appear bloating and pain. If the patient in the hemorrhoid surgery thirteen days later, there are still symptoms of wound swelling and pain, it is recommended that the patient go to the hospital in time to review, improve the relevant examination, clear the cause of the disease, and follow the doctor’s advice to give treatment.