After a colonoscopy is fine usually a stool test is also required. Colonoscopy is not a substitute for stool examination, certain mild inflammation, endoscopic mucosa may not have obvious lesions, through the routine examination of the stool, may find the presence of leukocytes or pus cells, etc., to clarify the inflammatory lesions of the intestinal tract. If there is an infection in the intestinal tract and the pathogen infecting the intestinal tract can be clarified by fecal pathogenicity testing, which guides the physician in treatment. Secondly, when there is slight bleeding in the intestines, colonoscopy may also fail to detect changes in the mucosa, and the presence of bleeding in the intestines can be clarified through fecal routine or fecal occult blood test. The colonoscopy mainly examines lesions in the colon and rectum, and does not provide a complete picture of the lesions in the small intestine. Stool examination, can assist in the diagnosis of small bowel disease. Stool examination can also provide changes in the shape, color and odor of the stool to help doctors identify the cause of the patient’s illness. Therefore, a stool examination is equally important and should be performed when no abnormalities are detected by colonoscopy. Patients should follow the doctor’s instructions, complete the relevant examinations under the doctor’s guidance, identify the cause of the disease, and carry out targeted treatment, so as to avoid delaying the condition.