Surgery is painful, and most patients respond that post-anal pain is even more memorable and even mentioned. Reasons for pain after anal surgery 1, anal sensory acuity: the anus is the exit of the digestive tract, because it bears the task of defecation, human beings in the long-term evolutionary process, so that the nerves innervating the anus are abnormally rich, the anus is locally more sensitive to various stimuli than other parts of the body. 2, anal sphincter spasm: the anal sphincter is divided into internal and external sphincter, the internal sphincter is mainly responsible for the role of closing the anus, is the continuation of the rectal wall muscles and terminals, belongs to the smooth muscle. When exposed to chemical and physical stimuli such as intestinal secretions, feces and surgical pulling, spasm will occur involuntarily, and the spasm will aggravate the local ischemia and edema of the anus, making the pain worse. 3. Defecation: The anus will repeatedly expand and contract during defecation, pulling on the surgical wound and aggravating the pain. At the same time, if the stool is abnormal, dry or diarrhea will also stimulate the wound. So many anal patients call post-operative defecation a hurdle, and some even control defecation by fasting in the hope of escaping it. But this is wrong. On the one hand, fasting leads to nutritional deficiencies that affect the healing of the wound, and on the other hand, the anus needs to be repaired in an “active” state in order not to affect its future function. Classification of post-operative anal pain 1. Traumatic pain: mainly occurs within a few hours after surgery and during and after defecation. Characteristically, the degree of pain is proportional to the number of surgical incisions and the size of the trauma, which will also gradually reduce or disappear with the extension of time. The peak of pain in the surgical wound of perianal abscess differs from that of other diseases, generally appearing about 5 days after surgery, mainly because the corrupted tissue of the abscess cavity is only shed at this time and the nerve endings are exposed. Thereafter, as the granulation grows and the nerve endings are covered, the pain will be reduced and disappear. 2.Sphincter spasm pain: It occurs within a few days after surgery and is severe and unbearable, with continuous or regular bouts of pain, some patients describe it as paroxysmal convulsion-like pain, which can be combined with difficulty in defecation and urination in severe cases. 3.Complication pain: It occurs suddenly within a few days after surgery, and the pain level is heavy, which will decrease with the extension of time. 4.scar pain: It is caused by the contracture of the scar after the healing of the surgical incision, and the heavier the scar, the more likely it is to appear. It usually appears after one month after surgery, and it is a transient pinprick-like pain, and the degree is not heavy.