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Colorectal cancer

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Symptoms of colorectal cancer

Colorectal cancer may not cause any signs or symptoms in its early stages because the cancer is very small. Symptoms often appear once a tumour grows into surrounding tissues and organs. Other health conditions can cause the same symptoms as colorectal cancer.

See your doctor if you have these symptoms:

  • diarrhea
  • constipation
  • stool that looks narrower than usual
  • feeling like the bowel is not completely empty after a bowel movement
  • blood in the stool (it can be bright or very dark red)
  • bleeding from the rectum
  • gas, cramping, bloating and feeling full
  • pain or discomfort in the rectum
  • a lump in the abdomen or rectum
  • fatigue and weakness
  • anemia, which may cause fatigue and shortness of breath
  • nausea and vomiting
  • loss of appetite
  • weight loss
  • blockage in the intestine (called bowel obstruction), which may cause pain in the abdomen
  • a tear or hole in the intestine (called bowel perforation), which may cause widespread infection (called sepsis)
  • frequent urinary tract infections
  • swollen lymph nodes
  • enlarged liver (called hepatomegaly)
  • jaundice (a condition in which the skin and whites of the eyes become yellow and urine is dark yellow)
  • buildup of fluid in the abdomen (called ascites)
  • pain in the abdomen, buttocks or leg
  • breathing problems


Researcher Dr Ming-Sound Tsao Dr Ming-Sound Tsao created a realistic lab model of lung cancer.

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Help for smokers trying to quit

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It’s okay to need help to quit smoking. The Canadian Cancer Society is here to support people who are ready to quit and even those people who aren’t ready.

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