The human intestinal tract is divided into the small intestine and the large intestine, the latter including both the colon and the rectum. Tumors that grow in the rectum and colon are collectively called colorectal cancer. Among them, cancer of the left half of the intestines (rectum, sigmoid colon and descending colon) accounts for 75%, cancer of the right half of the intestines (ascending colon) accounts for 20%, while cancer of the transverse colon accounts for only 5%. Rectal cancer has the highest incidence rate, accounting for about 60% of colorectal cancers. What is the age group of colorectal cancer? The incidence of colorectal cancer is mostly in the age group of 41-60 years old (the first peak period), followed by the age group of less than 40 years old (the second peak period), and the incidence rate is lower in the age group of 61 years old and above (the third peak period). The second peak group of colorectal cancer is mostly concentrated in the age of 25~35, so young people should not ignore colorectal cancer. Who are prone to colorectal cancer? Long-term constipation Long-term constipation causes feces to stay in the colon for too long, and the carcinogenic substances therein have a great impact on the mucous membrane of the intestinal wall. 2, long-term diarrhea people There are many reasons for diarrhea, one of them is colorectal polyps, if the polyps are not found for a long time, they can evolve into cancer. Therefore, patients with colorectal polyps must undergo regular colonoscopy. High protein and high fat food metabolites in the body can easily induce malignant changes of cells, which can trigger colorectal cancer. 4, Long-term inflammatory bowel disease patients If the treatment is not proper, the disease recurs many times, and the duration of the disease is more than 8 years, the patients should be alert to the occurrence of colorectal cancer. People with family history of colorectal cancer should pay attention to the symptoms of colorectal cancer at any time in all age groups with family history of this disease. Hemorrhoidal bleeding patients, some have polyps or cancerous tumors in the large intestine above the anus, if only bleeding symptoms are noted in the diagnosis, it is likely to miss the diagnosis of tumors occurring in the large intestine! It is recommended that anyone who has bleeding hemorrhoids must go to the gastroenterology department of the hospital in the near future to do a colonoscopy.