Western medicine recognizes that the onset of prolapse of the anal canal and rectum is closely related to generalized hypofunction and local factors of the pelvic floor. 1, incomplete development: the body is not yet mature during childhood, the pelvic floor support tissue is weak. In addition, the sacral bend has not been formed, the rectum is almost vertical. The rectum lacks strong support and support, so it is easier to move. If accompanied by malnutrition, chronic diarrhea or constipation, there may be separation of rectal mucosa and muscle layer, separation of rectum and surrounding tissue and rectal detachment. 2, physical weakness: various causes of severe malnutrition, long-standing illness and frailty or old age, due to a large reduction of fatty tissue between the gap around the anorectum, rectal ligament loosening, pelvic floor muscle group hypofunction, contraction weakness, perineum decline, resulting in the lack of effective fixation of the rectum, position down and prolapse. 3, increased abdominal pressure: chronic diarrhea, persistent constipation, prostate hypertrophy and long-term wheezing patients, due to the regular increase in abdominal pressure, resulting in the pelvic floor relaxation and decline, rectal prolapse. 4, pelvic floor muscle group injury: anorectal perineum surgery or trauma, as well as women’s production process may damage the pelvic floor muscle group and supporting tissue, or damage to the anal canal rectal ring, anal sphincter, thus losing the role of rectal support fixed, rectal prolapse occurs. 5, rectal prolapse pull: prolapsed internal hemorrhoids, rectal polyps, papillary fibroids, etc., because of repeatedly prolapsed outside the anus pulling the rectal mucosa down, can lead to separation of rectal mucosa and muscle layer, rectal mucosa prolapse. 6, neurological dysfunction: the influence of nerve injury or disease that innervates the anorectum and surrounding tissues, loss of function or decompensation, causing pelvic floor, perineum and anal sphincter relaxation and weakness, can also lead to prolapse of the rectum. The pathological changes of rectal prolapse: The pathological changes of rectal mucosal prolapse are the loosening of the submucosal layer of the lower rectum and the separation of the rectal mucosa from the rectal muscle layer. When defecation occurs, the rectal mucosa is pushed out of the anus with the feces. Increasing abdominal pressure can also cause it to prolapse out of the anus. At the beginning, the mucosa is mostly purple-red, smooth, soft and shiny. Later, due to repeated prolapse, the mucosa is constantly stimulated and becomes inflamed and edematous, and in severe cases, vesicles, superficial ulcers and punctate bleeding can be seen. Rectal mucosal prolapse has the possibility of self-healing, but most of them develop into total rectal prolapse. Total rectal prolapse is due to the loss of function of the pelvic floor muscles and supporting tissues, contraction weakness, perineum decline, loss of the role of rectal support, support and fixation, rectal downward movement, and eventually lead to the loosening of the lateral rectal ligaments, separation of rectum and sacrum, and prolapse of rectum out of the anus when the abdominal pressure is increased, and in severe cases, part of the sigmoid colon can be combined with prolapse. The mucosa of the prolapsed intestine is mostly congested and edematous. Due to repeated prolapse, frictional stimulation and poor hemolymphatic reflux, it often shows chronic inflammation, with erosion and ulcer formation, and easy bleeding. If the prolapse does not return for a long time, it may become embedded. Due to poor blood flow, the intestinal canal becomes enlarged and stagnant, and in serious cases, strangulated necrosis and intestinal perforation may occur. Due to the repeated prolapse of the intestine outside the anus, the anal sphincter is weak and relaxed due to long-term passive expansion and weak contraction. When the rectum prolapses, the anal canal can be turned out with it. Anal looseness also further aggravates rectal prolapse. There are two theories about the pathogenesis of rectal prolapse of the anal canal. 1. Sliding hernia theory: Moschcowitz proposed in 1912 that rectal prolapse is the process of hernia. Under the pressure of the abdominal viscera, the wrinkled wall of the rectal bladder trap or rectal uterine trap gradually sags, pressing the anterior rectal wall below it into the rectal pot belly, forming a hernia sac, which descends with the rectum and comes out of the anus. 2, intestinal overlap theory: Broden and Senllman 1968, that rectal prolapse is the sigmoid colon and rectum overlap in the b-rectal junction. The initial point of overlap is located at the highest point of the normal fixation of the rectum. Due to the pulling of the overlapping bowel, the upper end of the rectum separates from the sacrum, and the starting point of the overlap gradually descends with the rectal fixation point. Repeatedly, the fixation point of rectum and sacrum becomes lower and lower, and finally the sacrum is separated from the rectum and the rectum comes out of the anus.