A routine blood test after a patient has diarrhea can discern whether there is inflammation in the body, but not directly determine the specific cause of the disease. Routine blood test is a test to determine the blood condition and disease by observing the change in the number and morphological distribution of blood cells such as red blood cells, white blood cells, platelets and hemoglobin. For example, a high white blood cell count indicates an inflammatory infection in the intestinal tract, which can be considered as a cause of diarrhea. If you want to verify the specific cause of diarrhea, the following methods are often used: 1, routine stool: the preliminary determination of the presence of infection by testing the stool, intestinal infection is the direct cause of diarrhea; 2, colonoscopy: facilitate the diagnosis of terminal ileal lesions, this anatomical part still belongs to the intestine, lesions will also cause diarrhea; 3, X-ray examination: through barium meal examination or abdominal plain film X-ray examination: barium meal examination or abdominal plain film examination to clarify whether diarrhea is caused by gastrointestinal tract diseases; 4.