The following are some of the causes of anal swelling, 1, anal internal hemorrhoids, external hemorrhoids or mixed hemorrhoids, the onset of hemorrhoids to increase the chances of anal swelling, because the swelling of internal hemorrhoids, external hemorrhoids will cause the anus to go down, there will be a feeling of swelling. 2, rectal mucosa relaxation, rectal mucosa in the rectum internal mucosa relaxation to a certain degree, only to come off to the outside of the anus. Now with the improvement of people’s standard of living, rectal prolapse is very rare, but rectal mucosal prolapse is clinically more common, the onset of the main performance in the anal swelling, defecation is not clean, the stool strip is relatively thin and soft. In general, doctors who have studied rectal mucosal circumcision or TST or PPH will consider the etiology of endorectal mucosal prolapse.3. Uneven pressure in the anal canal, mainly involuntary spasm of the sphincter muscle, changes in rectal pressure in the anal canal, even if there is no stool inside the anus, the pressure in the anal canal will be great.4. Lesions in other systems, especially gynecological pelvic inflammatory disease and uterine fibroids, can compress the pelvis or compress the rectum, resulting in anal swelling.