There are many causes of anal swelling: the first one is more common is fecal retention, such as long-term fecal retention and difficulty in passing stool, which can lead to a large amount of stool being retained in the rectum, and the rectum will absorb the water of the stool thus leading to the generation of fecal stones, which, if formed, can lead to anal swelling. The second cause of anal swelling may also be endorectal or anterior rectal protrusion. The second cause of anal distention may be the endorectal sleeve or prolapse of the rectum. In this case, rectal examination or anoscopy should be performed in time to clearly see the loose mucosa. The third reason is that if the mixed hemorrhoids are heavy and combined with a lot of spicy and irritating food, or a lot of alcohol, it can lead to swelling of the hemorrhoid nucleus and stagnation of the hemorrhoid veins, resulting in anal swelling. So there are many reasons for anal swelling, which should be decided by combining physical examination, medical history and auxiliary examinations.