Colorectal cancer mainly occurs in the sigmoid colon and rectum, early signs include: 1. change in stool habits: variable and irregular timing, increasing or decreasing frequency. 2. 2. Alternation of diarrhea and constipation: unexplained and uncontrollable by medication, with loose stool or mucus stool for several days in a row, followed by several days of no stool. This situation frequently and repeatedly. 3, blood in the stool: can be invisible to the naked eye, occult blood positive, can also be and mucus stool stained with bleeding, but also on the surface of the stool with blood. When the above occurs, one should do a fecal occult blood test, and the other should be distinguished from hemorrhoids, never simply assume that bleeding stools are caused by hemorrhoids. 4, persistent abdominal pain, bloating discomfort or indigestion. If the above symptoms appear, you should immediately go to the gastroenterology department of a regular hospital for examination.