There is no obvious symptom in the early stage of rectal cancer, and the symptom appears only when it develops into ulcer or infection. 1.Symptoms of rectal irritation: discomfort of defecation, feeling of incomplete stool, feeling of anal drop, diarrhea, shortness of breath, and lower abdominal pain in advanced stage. 2.Symptoms of cancer infection: blood on the surface of stool, and in severe cases, purulent stool and increased number of stools. 3.Symptoms of intestinal wall stenosis: deformation and thinning of stool at the beginning. After the cancer causes partial obstruction of intestinal cavity, there are abdominal distension, paroxysmal abdominal pain, hyperactive bowel sounds and difficulty in stool. 4.Late stage of rectal cancer: invasion of prostate can cause frequent and painful urination; invasion of presacral nerve can cause severe and continuous pain; liver metastasis can cause cachexia such as hepatomegaly, ascites, jaundice, anemia, emaciation and edema.