The earliest stages of colorectal cancer have no symptoms. Colorectal tumors can grow slowly over the course of several years. This can cause subtle symptoms that only appear at later stages. If you have any of these symptoms, do not assume it is due to cancer. Symptoms can be caused by other, less serious conditions. However, it is still important to discuss them with your doctor. Early detection and treatment improve outcomes for cancer and other health issues.
Symptoms will vary by location of the tumor or how long it has been growing. The two most common symptoms of colorectal cancer are changes in bowel movements and blood in stool.
These may include:
Keep in mind that bowel habits and function are different for everyone. The changes you notice may be unique to you, but these are general changes to be aware of. If you detect changes that last at least 6 weeks, contact your doctor.
Tumors can cause bleeding, but sometimes it cannot be seen, especially if the tumor is in the first sections of the colon. If blood in the stool cannot be seen, it is called occult blood. There are specific tests that can detect occult blood in the stool.
Blood that is visible may appear as:
It should be noted that any rectal bleeding, with or without a bowel movement, should prompt a call to your doctor. Rectal bleeding can be caused by noncancerous conditions, such as hemorrhoids, which may require medical treatment.
Later stages of cancer may cause:
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Colorectal cancer. American Cancer Society website. Available at:
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Accessed February 27, 2020.
Colorectal cancer. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/colorectal-cancer. Updated January 22, 2020. Accessed February 27, 2020.
Glynne-Jones R, Wyrwicz L, Tiret E, et al. Rectal cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2017 Jul 1;28.
Last reviewed December 2019 by Mohei Abouzied, MD
Last Updated: 2/27/2020