1.Physical examination: determine the presence of abdominal pressure, abdominal tension, and whether the bowel sounds are hyperactive. 2.Laboratory examination: (1) Stool examination: including stool appearance, microscopy, and culture. Stool routine (red/white blood cells, protozoa, eggs, fat droplets) examination, occult blood test, stool culture, qualitative stool fat test (Sudan III staining), stool electrolyte or pH test are useful for etiological judgment. (2) Blood biochemical examination: including routine blood, electrolytes, total serum protein, C-reactive protein, erythrocyte sedimentation rate, can understand the patient’s infection with pathogenic bacteria, the presence of anemia and other manifestations. 3. Imaging examination: (1) X-ray barium meal or barium enema: observe the functional status of the whole gastrointestinal tract, and initially determine the presence of organic lesions. (2) Colonoscopy: access to the terminal ileum, direct observation of the colonic mucosa, feasible tissue biopsy if necessary. (3) Small intestine microscopy: it can be chosen when small intestine lesions are suspected or need to be excluded. (4) Capsule endoscopy: provides a non-invasive method for gastrointestinal examination, but it cannot be repeatedly observed, and the focus of observation cannot be set.