Thin stools are associated with intestinal inflammation, rectal polyps, intestinal tumors, and anal stenosis. During an attack of enteritis, the intestinal tract is hyperactive, so the contents of the intestine are eliminated quickly, and the food residues cause irritation to the rectum. The number of bowel movements increases during the disease, and the stool is not only thin, but also prolonged. If there is a large polyp in the rectum, it will squeeze the stool during defecation, so the stool will come out relatively thin. When intestinal tumors appear in the colon or rectum, the feces will be squeezed by the tumor after formation, and the feces will be mainly flat and thin, and some people’s feces will even look like a water belt. Some people have narrowed anal canal, and the stool will be relatively thin when passing through the anal canal, so these people will not only have thin stool, but also have increased possibility of fissure.