The development of rectal cancer will cause the following symptoms: 1. Extensive infiltration of tumor in the pelvis will lead to lumbosacral pain, sciatica and atresia. 2. Forward infiltration of tumor into the mucosa of the vagina and bladder will lead to vaginal bleeding or hematuria, and in severe cases, rectovaginal fistula and rectovaginal fistula may occur. 3. Bilateral ureteral obstruction will lead to urinary closure and uremia, and tumor compression of the urethra will also lead to urinary retention. 4. Tumor compression of urethra may also lead to urinary retention.4. Ascites, obstruction of lymphatic tract or compression of iliac vein may lead to edema of lower limbs, scrotum and labia.5. Intestinal perforation may lead to acute peritonitis and abdominal abscess.6. Distant metastasis, such as liver metastasis, may lead to hepatomegaly, jaundice and ascites, lung metastasis may lead to cough, shortness of breath and bloody sputum, brain metastasis may lead to coma, bone metastasis may lead to bone pain, etc.7. Bone metastases may lead to bone pain, etc. 7. They may cause cachexia and systemic multi-organ failure.