Colorectal cancer is a common malignant tumor of gastrointestinal system that seriously endangers human health. In recent years, its incidence rate and mortality rate have shown a rapid increase worldwide, and its incidence rate ranks the 3rd among malignant tumors and mortality rate ranks the 4th among malignant tumors. According to the information published by the World Health Organization IARC, there were 1,200,000 new cases of colorectal cancer worldwide in 2008, and the number of deaths was half of the number of cases. In China, with the change of living environment and diet, the mortality rate of colorectal cancer has also increased rapidly. The incidence rate of colorectal cancer in China has been comparable to the world average, and the incidence rate ranks the fourth in malignant tumors and the mortality rate ranks the fifth, while in Beijing, the incidence rate has ranked the second in male malignant tumors. Second, who should be alert to the occurrence of colorectal cancer? Early detection and early treatment are the principles of diagnosis and treatment for all tumor patients. According to the authoritative SEER data of the United States, the 5-year survival rate of colorectal cancer with tumor limitation is as high as 90.1%, while that of those with regional lymph node metastasis is 71.2% and that of those with distant liver and lung metastasis is only 13.5%, which shows how important early detection and early diagnosis and treatment are. However, early diagnosis does not seem to be optimistic at present. Information shows that the earliest staged stage I colorectal cancer in China accounts for only 11.8%, while the United States accounts for 39%. A very important reason for the difficulty of early detection of colorectal cancer is that colorectal tumors do not have specific symptoms in early stage, and it is difficult for patients to choose to visit hospitals through symptoms. However, some people, who are at high risk of colorectal cancer, should be more alert to the occurrence of colorectal cancer, and even if they have no symptoms, they need to take the initiative to do some tests regularly, including fecal occult blood and colonoscopy, etc. For patients over 40 years old, they should be highly alert to the possibility of rectal cancer and must seek medical consultation in time if they have the following conditions: Grade I relatives with history of colon or rectal cancer; history of intestinal polyp, adenoma or cancer; persistent positive fecal occult blood; mucus blood in stool; and mucus blood in stool. Positive fecal occult blood; history of mucus and blood stool, chronic constipation, chronic diarrhea, etc. We suggest that patients who are in a position to do so should have a colonoscopy once a year. What are the common symptoms of colorectal cancer? Colorectum is the collective name of colon and rectum, which is generally divided into right hemicolectum (cecum, ascending colon, right side of transverse colon), left hemicolectum (left side of transverse colon, descending colon and sigmoid colon) and rectum. Patients with right hemicolectomy can show early loose stools with increased frequency, and alternate diarrhea and constipation as the mass increases; tumor rupture and bleeding and malnutrition can cause anemia, and unexplained anemia is also a point we need to be alert to. Due to insidious symptoms and untimely detection, many patients can palpate the right abdominal mass. For patients with left hemicolectomy tumor, because the left hemicolectomy is thinner than the right hemicolectomy, and the stool to the left hemicolectomy has been partially “processed” by the large intestine and absorbed most of the water, so the water content of stool is relatively lower, so the symptoms such as difficulty in defecation, stool with blood, mucus and intestinal obstruction can appear at the early stage of tumor growth. The bleeding volume of left colon cancer is relatively small, usually bright red, and the symptoms of malnutrition and anemia are less frequent in early stage. The characteristics of both of them also determine the higher early detection rate of left hemicolectomy than right hemicolectomy. For rectal cancer, the symptoms are more obvious, such as blood in stool, more frequent stools, frequency and incomplete feeling, etc. Blood in stool is the most common, accounting for 80% of the symptoms of rectal cancer, and it is very important to distinguish blood in stool of rectal cancer from hemorrhoids. What is the difference between blood in stool of rectal cancer and hemorrhoids? Simply put: Rectal cancer blood in stool is characterized by: mucus dark red blood stool and mixed blood in stool; while hemorrhoid bleeding is characterized by: dripping or spraying fresh blood and separation of blood in stool. Fourth, should I see gastroenterology or gastrointestinal surgery when I have the above symptoms? This is usually a problem that people struggle with. First of all, you should know the scope of practice of internal medicine and surgery, gastroenterology to treat diseases, including diarrhea, enteritis, gastrointestinal dysfunction, ulcer medication, etc. In general, gastroenterology is a department that treats digestive tract diseases with drugs. If you have the above symptoms, you should first consult the gastrointestinal surgery department to rule out the possibility of tumor through examination, and if you are diagnosed with tumor, you should consult the surgery department. Of course, for some early stage cancers, after precise staging, colonoscopic resection in gastroenterology will be recommended.