Abdominal CT plain scan + enhanced examination can basically exclude rectal cancer if it shows that the rectum is fine, but a definitive diagnosis requires proctoscopic pathologic biopsy. Abdominal CT is the main means of abdominal organ examination. Through abdominal CT scanning + enhancement examination, some early lesions can be found, which is of strong guiding significance for the early examination of rectal cancer. Abdominal CT plain scan + enhancement can understand the location, shape, size and relationship with surrounding organs of rectal cancer. Therefore, when abdominal CT examination is fine, rectal cancer can be basically excluded. Most rectal cancers, especially early rectal cancers, are difficult to be characterized by abdominal CT examination, and the gold standard for its examination is proctoscopic tissue biopsy, which can only be assured when the result suggests normal. It is suggested that patients should follow the doctor’s instructions to give relevant examinations according to the needs of their conditions so as not to miss them.