Colorectal cancer sometimes arises without any symptoms. For this reason, screening tests (such as colonoscopy and a test for blood in the stool) are recommended to detect the cancer early, when it is more curable.
When symptoms do occur, however, they may include the following:
- rectal bleeding or blood in the stool
- a change in bowel habits (such as diarrhea, constipation, or narrowing of the stool) that lasts for more than a few days
- abdominal pain
- a continuous feeling that you need to have a bowel movement, which does not resolve after passing stool
- weakness
Some of these symptoms may be caused by other conditions. But you should see your doctor if they persist. Any incidence of rectal bleeding or blood in the stool should be brought to your doctor's attention.