One side of the stool is round and the other side is flat, which may be related to physiological factors or pathological factors such as hemorrhoids and anal space occupation. 1. Physiological factors: if the patient has no other discomfort when defecating, it may be caused by the fecal water, fiber content is more causes of feces through the anus by extrusion caused by the deformation of the situation, so there may be the phenomenon of one side of the stool is round and one side of the phenomenon of flat, which belongs to the normal physiological factors. 2. Pathological factors: (1) hemorrhoids: one side of the stool round side flat may be due to hemorrhoids, when the hemorrhoids are large when the stool through the anus, may be due to the hemorrhoids of the extrusion caused by deformation of the situation, the formation of the stool side round side flat phenomenon. (2) anal occupancy: anal occupancy can also lead to one side of the stool round and one side flat, mainly due to swelling caused by the intestinal content of the intestinal canal to reduce the size of the patient to such a situation, and accompanied by the phenomenon of blood in the stool. Excluding normal physiological factors, if the patient has a flat stool with one side rounded, it is recommended to go to the hospital in time, under the judgment of the doctor to clarify the cause of the disease and carry out the correct treatment.