Bowel cleansing usually refers to the preparation of the bowel prior to a colonoscopy and is categorized into four grades, A, B, C, and D, based on the presence or absence of fecal matter in the bowel. Grade A criteria is when the patient has no fecal matter in the bowel and only a small amount of clear fluid. Grade B criteria are patients with only a small amount of fecal matter or a small amount of clear fluid in the bowel, which usually does not interfere with microscopy and observation. Grade C criteria are intermittent moderate amounts of fecal fluid in all segments of the bowel, but can be observed without difficulty by aspiration, change of position, etc., without affecting the results of the examination. Grade D indicates that the bowel preparation is substandard, and the patient’s intestines are not clean, with a large amount of turbid fecal water or dilute stools, which can still not be observed smoothly by suctioning or changing the position, which seriously affects the examination results and does not allow smooth observation of the specific conditions in the intestines. The color of the discharged fecal water and the amount of fecal sludge can also indirectly determine the degree of intestinal cleansing, with watery stools as the best. The specific situation also needs to be judged by a professional physician. In order to avoid poor preparation affects the test results.