Most early stage rectal cancer is asymptomatic. Patients with progressive cancer (middle and late stage) show symptoms such as abdominal pain, blood in stool, thinning of stool and diarrhea. Rectal cancer can show blood in stool when it grows to a certain extent. A small amount of bleeding is not easily detected by the naked eye, but a large number of red blood cells can be found when the stool is examined by microscope, and the so-called fecal occult blood test is positive. When there is a large amount of bleeding, it can appear as blood in the stool with bright red or dark red color. When the cancer surface breaks down and forms ulcers, and the tumor tissue is necrotic and infected, pus and blood, mucus and blood stools may appear. Patients may have different degrees of incomplete stool feeling, anal drop feeling, and sometimes diarrhea. When rectal tumor causes narrowing of intestinal lumen, symptoms of intestinal obstruction (abdominal pain, abdominal distension, difficulty in defecation) may appear in different degrees. The stool may become thin and grooved. When tumor invades bladder and urethra, frequent, urgent, painful urination and difficulty in urination may occur; when tumor invades vagina, rectovaginal fistula and fecal fluid may appear; when tumor invades sacrum and nerves, severe pain in sacrococcygeal area and perineum may appear; when tumor invades and presses ureter, swelling and pain in lumbar area may appear; when tumor also presses external iliac vessels, edema of lower limbs may appear. All the above symptoms indicate that the tumor is in advanced stage. When the tumor metastasizes distantly (liver, lung, etc.), symptoms may appear in the corresponding organs. For example, dry cough and chest pain may appear when the tumor metastasizes to the lung. Patients may have different degrees of weakness, weight loss and other symptoms. Patients with the above symptoms (abdominal pain, blood in stool, thinning of stool and diarrhea) are recommended to go to the anorectal clinic of regular hospitals, not to attribute the above symptoms to hemorrhoids. Many patients have delayed treatment because of treating rectal cancer as hemorrhoids.