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What Are the Symptoms?

In its early stage, colorectal cancer usually produces no symptoms. The most likely warning signs include:

• Changes in bowel movements, including persistent constipation or diarrhea, a feeling of not being able to empty the bowel completely, or rectal bleeding
• Dark patches of blood in or on stool; or long, thin, "pencil stools"
• Abdominal discomfort or bloating
• Unexplained fatigue, or loss of appetite or weight.

• You notice a change in your bowel movements, experience bleeding from the rectum, or notice blood in or on your stool. Don't assume you have hemorrhoids; your doctor will most likely perform a rectal examination and possibly a sigmoidoscopy or schedule a colonoscopy — an examination that involves a long flexible tube inserted in your rectum.
• You experience persistent abdominal pain, unusual weight loss, or fatigue. These symptoms may be due to other causes, but they could also be linked to cancer.
• You are diagnosed with anemia. In determining its cause, your doctor should check for bleeding from the digestive tract because of colorectal cancer.