Most of them have perianal diseases, such as external hemorrhoids, mixed hemorrhoids, anal fistulas, etc., which cause uneven skin at the anal edge, sometimes with painful conditions, and therefore often lead to unclean wiping of the buttocks after defecation. There are also some people with normal anal appearance, but there are polyps or large internal hemorrhoids, or because of the age of the anal sphincter muscle relaxation, or previous anal trauma or surgery, the scar is large, this part of the people often anal sphincter muscle is not closed tightly, resulting in a small amount of mucus and other secretions outflow, often contaminated underwear, is not considered to wipe the butt clean. This situation can be solved by cleaning the anus after the stool, doing more anal lifting exercises and exercising the anal sphincter, but in serious cases you need to go to the hospital to see a doctor.