CT can detect most of the intestinal tumors. CT can detect the size of intestinal tumors and the layer of intestinal wall invaded by intestinal tumors, and it can also directly observe whether the tumors invade other organs and tissues such as pelvic muscles, bladder or prostate. Meanwhile, CT can also detect metastatic lymph nodes with a diameter of 1-2cm or more, but it is more difficult to detect small lymph nodes on CT; and if the tumor is especially small, it is often difficult to detect on CT as well. Therefore, when there is blood in stool, thin or deformed stool, change of stool habit, abdominal pain and other discomfort, besides CT, you need to do electronic colonoscopy, which can detect small tumors in the intestine.