The bowel movement is normal at the beginning and becomes flat at the end, which is usually considered to be a physiological phenomenon. However, if it is caused by hemorrhoids, colorectal polyps, rectal cancer and other diseases, it is not normal. 1. Physiological phenomenon: because when the stool is stored in the large intestine, different locations of the feces absorb water differently, so there will be a normal stool at the beginning of the back of the flattening of the situation, indicating that the back of the feces in the water is more, which is a normal situation. 2. hemorrhoids: the etiology of this disease is not yet clear, but clinically there is an anal cushion under the theory and varicose vein theory, common triggering factors are bad defecation habits, low-fiber diet, long-term constipation or diarrhea and so on. As hemorrhoids manifest as enlargement of the venous plexus of the anal canal or lower rectum, so in the process of fecal discharge, may change the shape of the stool, appearing in the stool at the beginning of the normal behind the flattening of the situation. 3. Colorectal polyps: Studies have shown that the causes of this disease include genetics, poor eating habits, advanced age, and other underlying diseases, such as ulcerative colitis and Crohn’s disease. Generally small polyps are asymptomatic, but when the polyps are large, it will change the stool characteristics and defecation habits, so some patients will have the phenomenon that their stools become flat after being normal at the beginning. 4. Rectal cancer: this disease is mostly evolved from adenomatous polyps, which is the result of environment, diet, living habits and genetic factors. Generally speaking, there are no obvious symptoms in the early stage, but when the disease develops to a certain stage, patients will not only have the phenomenon that the stool becomes flat behind the normal stool at the beginning, but also have the phenomenon of anxiousness (discomfort in the lower abdomen, wanting to defecate very much, and feeling of incomplete defecation after defecation), incomplete defecation, and bleeding, etc. It is recommended to have the phenomenon that the stool becomes flat behind the normal stool at the beginning. It is recommended that patients with bowel movements that start out normal and then flatten out should go to the hospital in a timely manner in order to clarify the cause of the problem.