The human intestine is divided into small intestine and large intestine, and the latter includes both colon and rectum. Tumors growing in the rectum and colon are collectively called colorectal cancer. Among them, cancer of the left hemithorax (rectum, sigmoid colon and descending colon) accounts for 75%, cancer of the right hemithorax (ascending colon) accounts for 20%, and cancer of the transverse colon accounts for only 5%. Rectal cancer has the highest incidence rate, accounting for about 60% of colorectal cancer. Age group of colorectal cancer incidence Colorectal cancer incidence mostly occurs in people aged 41-60 years old (first peak), followed by people under 40 years old (second peak), and the incidence rate above 61 years old is low (third peak). The second peak of colorectal cancer is mostly concentrated in the age of 25~35, so young people should not ignore colorectal cancer. Who are vulnerable to colorectal cancer (1) 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) People with long-term diarrhea There are various causes of diarrhea, one of which is colorectal polyps, which can turn into cancer if left undetected for a long time. Therefore, patients with colorectal polyps must undergo regular colonoscopy. (3) Long-term high-fat diet The metabolites of high-protein and high-fat food in the body can easily induce cell malignancy, which can lead to colorectal cancer. (4) Long-term inflammatory bowel disease Patients with improper treatment, multiple relapses and disease duration of more than 8 years should be alert to the occurrence of colorectal cancer. (5) People with family history of colorectal cancer People of all ages with family history of this disease should pay attention to the appearance of colorectal cancer symptoms. (6) People with bleeding hemorrhoids Some patients with bleeding hemorrhoids have polyps or cancerous tumors in the large intestine above the anus, and if only the bleeding symptoms are noticed in the diagnosis, it is likely that the tumor in the large intestine will be missed! It is recommended that anyone with bleeding hemorrhoids must go to a hospital gastroenterology department for a colonoscopy in the near future.