Generally, thyroid cancer does not cause bleeding in stool after surgery, but if there is blood in stool, it should be considered to be related to hemorrhoids, anal fissure, rectal polyps or intestinal tumors. 1. Hemorrhoids: such as internal hemorrhoids, early painless post-stool bleeding can occur, which can be in the form of blood spurting or dripping, with dry stool or constipation as the causative factors. 2. Anal fissure: if there is fecal dryness, defecation caused by stool mechanical damage to the anus, anal pain, blood in the stool and other manifestations. 3. Rectal polyp: Rectal polyp can be asymptomatic when it is small, and after it increases in size, it can have the performance of stool with dark red or bright red blood, and complicated with infection, it can cause mucous pus and blood stool. 4. Intestinal tumor: For example, rectal cancer patients have symptoms such as change of bowel habit and character, abdominal pain and blood in stool. After thyroid cancer surgery, patients with blood in stool can consult doctor in time, clarify the cause of blood in stool, and follow the doctor’s instruction for treatment; after thyroid cancer surgery, they need to have lifelong follow up and regular re-consultation.