A US data prompt, collected from the National (US) Endoscopy Database from 2000 to 2012, in 65,892 patients aged 40-49 years who underwent colonoscopy for various indications. A higher percentage of patients with blood in the stool had larger polyps (>9 mm) or tumors compared to controls! If the blood in the stool is bright red and attaches to the surface of the stool in drops, then the bleeding is mostly in the anus or not far from the anus, and bleeding from hemorrhoids, anal fissures, giant polyps, and rectal cancer should be considered. Bowel cancer can be asymptomatic in early stage and early diagnosis depends on regular colonoscopy! Generally speaking, people above 40 years old, but nowadays, tumors are trending younger, and it is not uncommon to have bowel cancer in the age of 10 or so. For long-term manifestations of the following (more than 2 months), it is worth to draw attention: 1. Blood in stool: early lesions of bowel cancer are limited to mucosa, which can be asymptomatic or only have changes in bowel habits. When the tumor grows to a certain extent, blood in stool can appear, which is mostly light in color and adheres to the surface of stool. Red blood cells can be found in the stool microscopy and the fecal occult blood test is positive. For people with bloody stools or persistent positive fecal occult blood, the possibility of colorectal tumors should be considered first, and further relevant tests should be done. 2.Mucus stool and pus-blood stool: When a huge polyp or cancer ruptures, the stool often has bright red or dark red blood and mucus, and the feces and blood are mixed. 3.Changes in bowel habits: the number of stools changes from once a day to two or three times a day, and there is a feeling of incomplete stools after each stool. 4. Alternation of diarrhea or constipation: If there are symptoms such as alternation of diarrhea and constipation, it may be because the growth of tumor affects the normal physiological function of intestine, and should be considered as possible tumor. 5. Lower and middle abdominal pain and abdominal distension: Patients with intestinal cancer will suffer from abdominal distension and abdominal pain due to intestinal obstruction, among which the incidence of abdominal pain is higher than that of abdominal distension. The location of pain is mostly in the lower and middle abdomen, and the degree of pain varies, mostly hidden pain or distension. 6. Anemia and wasting: As the disease progresses, patients may develop chronic wasting symptoms, such as anemia, wasting, weakness and fever, and even cachexia, often accompanied by fatigue and unexplained sudden weight loss, associated with blood in stool, insufficient intake and excessive consumption. It is best to go for colonoscopy when there are above manifestations, which is the most effective and preferred means for early diagnosis of colorectal cancer and precancerous lesions.