I. What diseases should be considered for pain related to defecation (1) Anal fissure: the pain is characterized by burning pain in the anal region at the beginning of defecation, which is more intense after defecation than before and lasts for several minutes to several hours. (2) Strangulated internal hemorrhoid: a swelling prolapses from the anus during defecation and cannot be retracted, and severe persistent pain occurs with a history of internal hemorrhoid prolapse. (3) Anal sinusitis: the pain is mild, often a few minutes after defecation, and can disappear on its own. (2) What diseases should be considered for pain unrelated to defecation (1) Perianal infection: persistent pain and increasing distension in the anus or anal canal, often accompanied by inflammatory manifestations, such as fever and increased white blood cell count. (2) Thrombosed external hemorrhoid: The patient suddenly feels a spherical mass, purple or black in color, appearing at the edge of the anus, caused by the rupture of perianal veins, accompanied by persistent and severe pain, which is aggravated when walking or standing. (3) Anal canal cancer: there is often mild persistent stabbing pain in the anal region, and in the late stage, the whole body is in poor condition, and a hard lump can be felt in the anal canal. (4) Foreign body in the anal canal: such as chicken bone pieces, bamboo spines, fish bone spines, etc. enter the anal sinus and cannot be discharged, while the pain in the anal region is suddenly severe, persistent and worsens when defecating, and patients usually do not have blood in the stool or inflammatory manifestations. The diagnosis can often be made by rectal examination (sometimes rectal examination under local anesthesia is required). Excessive consumption of chili peppers, garlic, mustard, alcohol, etc., contains irritating components in the stool, which can also cause pain and discomfort in the anus. According to the World Health Organization, in recent years there has been a trend towards the prevalence of sexually transmitted diseases in the anus, rectum and colon, such as cytomegalovirus (CMV) ulcerative proctitis, which is a common disease in homosexual men. The main manifestations are anorectal pain, burning sensation, anal itching, mucus and blood stools, and urgency. Endoscopic examination reveals rectal mucosal ulcers ranging from superficial punctate lesions to relatively deep fused ulcers with the entire ulcer covered by a light yellow and white wound membrane. Multiple bites for tissue biopsy and viral culture can confirm the diagnosis. Surgeons must also be familiar with the manifestations and early diagnostic techniques of these diseases in the anus and rectum. V. Chronic anal pain (1) Perineal descent syndrome: Perineal descent syndrome is a pelvic floor disorder caused by degeneration and dysfunction of the pelvic floor muscles from various causes, which occurs when the perineum descends beyond the normal range during forceful defecation. parks (1996) first described this disease and considered this syndrome as a concomitant symptom of rectal prolapse. The main cause is directly related to excessive straining to defecate. Common symptoms are characterized by a feeling of unclean bowel movements, anal swelling, difficulty in defecation and perineal pain. (2) Pelvic floor dyslaxation syndrome: pelvic floor dyslaxation syndrome used to be named puborectalis syndrome, and the late pathological changes were mainly spastic hypertrophy of the puborectalis muscle. 1985 Kuijpers was named pelvic floor dyslaxation syndrome, which was thought to be caused by normal muscle dysfunction. The main clinical symptom is slow progressive defecation difficulty, defecation can take up to several hours, very painful. (3) Endorectal prolapse: Severe endorectal prolapse often causes chronic anal pain, and endorectal prolapse caused by endorectal fornix can stretch the rectal vault and produce a sense of urgency, thus leaving the internal sphincter in a state of prolonged tension and spasm. Anal pain in such patients may be secondary to ischemia-reperfusion injury of the anal canal caused by pathological hypertrophy of the internal sphincter.