I've Been Constipated. Could I Have Colon Cancer?

A doctor goes over a patient''s x-ray, screening for colon cancer. Getty Images North America

I'm usually able to have a bowel movement at least two times per week. For the past three weeks, I haven't been able to have a bowel movement on my own. I've been taking a laxative once a week. Can this be a sign of colon cancer?

Is Constipation a Sign of Colon Cancer?

It's good that you're paying attention to what's a normal schedule for you. Constipation is usually defined as fewer than three bowel movements per week.

Chronic constipation without a specific cause is experienced by as many as 14% of the population, and by more women than men. A change in your bowel habits is a sign that something is going on in your body, and it's wise to check it as a medical symptom.

Given the high number of people in the population with constipation, it's a leap to think the cause is cancer rather than more common causes, such as a change in your diet, lack of exercise or that you are dehydrated.

Most often, colorectal cancer has no symptoms at all. This is why regular screening with a fecal occult blood test is done, as well as screening colonoscopy at age 50 and regular intervals. Guidelines for detecting colorectal cancer don't include constipation as a reason for further diagnostic testing. If that is your only symptom, your doctor is justified in not sending you for a colonscopy, unless you were due for one as a screening test.

While not the first thing you should suspect, constipation can be a sign of colorectal cancer. Tumors in the left colon, sigmoid colon, and rectum can sometimes block the flow of solid stool, leading to difficulty having bowel movements.

While there has been speculation in the past that chronic constipation is a risk factor for colorectal cancer, a large meta-review of studies in 2013 found no increase in the prevalence of colorectal cancer in people with constipation.

This was especially shown in studies that tracked people for six to 12 years.

What is Causing Your Constipation?

There's always a reason for constipation, even if it's not cancer. Have you been eating differently these past few weeks? Less fiber, more white stuff (bread, rice, pasta), more cheese? Have you exercised less? Have you been sweating more, drinking less, or have other risks for dehydration? All of those things can lead to constipation, too.

Any change of bowel habits is worth discussing with your doctor. It may not be cancer, but it could be something that needs attention and treatment. It is also a good time to get caught up on all of your screening tests and preventative health procedures, such as immunizations. Depending on your age and other factors, your doctor may recommend colon cancer screening. At the very least, you'll get some professional medical advice (which I can't provide) about the problem you're having.
Sources:

Suares NC, Ford AC "Prevalence of, and risk factors for, chronic idiopathic constipation in the community: systematic review and meta-analysis. Am J Gastroenterol. 2011 Sep;106(9):1582-91; quiz 1581

Constipation - Gastrointestinal Complications-for health professionals (PDQ). Updated January 4, 2016. National Cancer Institute at the National Institutes of Health. Accessed 2/9/2016.

Power AM, Talley NJ, Ford AC. "Association between constipation and colorectal cancer: systematic review and meta-analysis of observational studies." Am J Gastroenterol. 2013 Jun;108(6):894-903; quiz 904. doi: 10.1038/ajg.2013.52. Epub 2013 Mar 12.

Symptoms and Causes of Constipation. November 13, 2014.  National Institutes of Health.  Accessed February, 2016. http://www.niddk.nih.gov/health-information/health-topics/digestive-diseases/constipation/Pages/symptoms-causes.aspx

Douglas K. Rex, et. al. "Colorectal Cancer Screening, Guideline. American College of Gastroenterology" Am J Gastroenterol 2009, 104: 739-750.

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