Enteroscopy can only observe whether there are organic lesions on the surface of the intestinal tract, and cannot clarify functional diseases, while both organic and functional diseases can cause diarrhea. 1. Organic diseases: common diseases that can cause diarrhea include ulcerative colitis, Crohn’s disease, intestinal tuberculosis, etc. Other diseases may also cause diarrhea, such as small bowel disease and hyperthyroidism. 2. Functional diseases: common including irritable bowel syndrome, intestinal spasm, etc., the patient may manifest as diarrhea, but colonoscopy can suggest normal, need to treat the symptoms. It is recommended that patients go to the hospital in time after diarrhea, to clarify the nature of the disease and symptomatic treatment.