How to detect colorectal tumor in early stage? Many patients encountered in the gastroenterology clinic have changes in stool habits, many of them complained that their stools were normal in the past, but now their stools are not normal, and as a result, colon cancer was found after colonoscopy, and some of them have already metastasized and lost the time for surgical resection. Therefore, it is very necessary to raise the awareness and screening of colorectal tumors. The colon is divided into two parts: colon and rectum, which are mainly located in the lower right, lateral abdomen, upper abdomen, left abdomen, lower abdomen and up to the anus. Colorectal cancer is one of the most common malignant tumors in the world, and its incidence rate is currently ranked the 3rd in global malignant tumors. With the change of diet and living habits of Chinese residents, its incidence rate is gradually increasing. According to the report of China Center for Disease Control and Prevention in 2007, the death rate of colorectal cancer in China ranks the 3rd among malignant tumors in women and the 4th in men. Minister Chen Zhu pointed out in the report of the third national retrospective sample survey on causes of death in 2008 that the overall incidence of colorectal cancer in China has increased by 36.7% in recent years. Timely detection of precancerous lesions and early tumors can significantly reduce the incidence and mortality rate of colorectal cancer. Timely treatment of precancerous lesions can reduce the chance of cancer and lower the incidence of colorectal cancer; endoscopic resection of early colorectal cancer can approach the state of cure; the 5-year survival rate is over 90%. Raising awareness of colorectal cancer is not only the responsibility of specialist physicians, but also other professional doctors and the general public should pay full attention to colorectal cancer. The warning signs of colorectal cancer are change in stool habits and nature, as well as abdominal pain, loss of appetite, weakness and emaciation. Clinical manifestations are ① persistent change in bowel habit, diarrhea or constipation, or alternating diarrhea and constipation; ② recent persistent abdominal discomfort, vague pain and abdominal distension; ③ unexplained blood in stool or blood and mucus in stool; ④ unexplained anemia or significant weight loss; ⑤ abdominal mass. In the late stage, cachexia, ascites, jaundice, hepatomegaly, huge abdominal mass, severe pain in the anorectal area, and difficulty in urination may appear. When there are the above symptoms, you should seek medical consultation in time. Screening is an effective method to enhance the early diagnosis of colorectal cancer, which can effectively reduce the incidence and mortality rate of colorectal cancer, and it can carry out primary and secondary prevention. The scientific screening method should be able to identify the early symptoms, signs and pathological changes in the body of the disease, with the characteristics of rapid, safe, reliable, easy, less painful and less costly, and easy to be accepted by the examiner and the examined. At present, a simple, economical, non-invasive test with certain positive findings is the fecal occult blood test (FOBT). The most commonly used fecal occult blood tests are chemical methods (including the o-toluidine method, latent blood powder method, guaiac method) and immunological methods (colloidal gold labeled immunoassay, immunoturbidimetric method, etc.). The traditional chemical method is low cost, but has many false positives and low sensitivity. The emerging immunocolloid gold method and immunoturbidimetric method are slightly more costly, but are increasingly widely used because of their good specificity. Of course, the only direct method to detect colorectal tumors is colonoscopy, and colon polyps (precancerous lesions) can be removed under colonoscopy, so colonoscopy is both a screening tool and the “gold standard” for colon cancer diagnosis. We suggest that e-colonoscopy should be performed for people with alarm symptoms in the high-risk group of colon and rectal cancer. The recommended screening criteria are as follows: age ≥ 40 years, history of colorectal cancer and intestinal polyps in first-degree relatives; history of intestinal polyps or cancer in oneself; ulcerative colitis or Crohn’s disease for more than 10 years; biliary tract disorders and gallbladder removal for more than 10 years; history of lower abdominal radiotherapy for more than 10 years; history of chronic schistosomiasis in the colon, meeting one or more of the following two items: ① Positive fecal occult blood by immunoassay ( colloidal gold test paper method); ② 2 or more of the 6 items such as chronic diarrhea, chronic constipation, mucus and blood stool, change in stool habit, chronic appendicitis and history of mental irritation.