Are your symptoms IBS or colorectal cancer?

Last updated Oct. 4, 2021

Colorectal cancer shares some symptoms with a less serious, but much more common disease: irritable bowel syndrome (IBS). So how do you know if your symptoms are cancer, IBS or something else?

We talked to David Richards, M.D., about the symptoms of irritable bowel syndrome and colorectal cancer, and what action you should take if you are experiencing either.

What are the symptoms of irritable bowel syndrome?

IBS can be hard to diagnose. It’s not something a doctor can see, feel or detect under a microscope, and the symptoms come and go. The main symptoms of IBS are constipation, diarrhea or a combination of the two, accompanied by abdominal pain.

Someone with IBS may also experience one or more of the following:

• Abdominal bloating
• Mucus in your stool
• The feeling that you haven’t finished a bowel movement
• Relief of symptoms after a bowel movement

You can gauge whether these are IBS symptoms based on how long you’ve had them. “The symptoms have to go back at least six months, with at least one day a week of pain in the last three months,” Richards says.

What are the symptoms of colorectal cancer?

Diarrhea, constipation and abdominal pain are all symptoms of colorectal cancer. However, there are additional symptoms that are more concerning.

“Sudden and unexplained weight loss, rectal bleeding or blood in the stool are all cause for concern,” says Richards.

Other colorectal cancer symptoms include:

• A change in the size or shape of your stool, which may suddenly be thin like a pencil
• A new need for straining to evacuate stool
• Fatigue
• Discomfort or urge to have a bowel movement when there is no need
• Bloating or feeling full constantly
• Change in appetite

“I would be especially concerned if these symptoms came on suddenly,” says Richards.

When should you see a doctor about symptoms?

Symptoms lasting more than two weeks should trigger a trip to the doctor. Based on your age, symptoms and family cancer history, your doctor will decide if you need a diagnostic test like a colonoscopy or CT scan.

In addition to colorectal cancer, your doctor will want to rule out inflammatory bowel disease (IBD). This family of disorders shares symptoms with IBS and colorectal cancer.

The two most common inflammatory bowel diseases are ulcerative colitis and Crohn’s disease. These are autoimmune diseases that inflame the GI tract. This prolonged inflammation raises the risk of colorectal cancer.

“A lot of the concerning symptoms may not be cancer, but they could be something more than IBS,” says Richards.

Does IBS affect your cancer risk?

Unlike IBD, IBS does not cause inflammation, a key factor in colorectal cancer risk.

“IBS does not raise your risk for colorectal cancer, no matter how long you’ve had it,” says Richards.

What should cancer patients know about IBS?

A lot of cancer treatments can trigger stomach issues. For example, traditional chemotherapy affects any rapidly dividing cells, including cells in the GI tract. So, blood in the stool and abdominal pain are not uncommon.

If you are in cancer treatment or about to start treatment, talk to your doctor about side effects that you might experience and how to manage potential GI side effects.

When is colorectal cancer screening needed?

Men and women at average risk for colorectal cancer should get a screening colonoscopy every 10 years beginning at age 45. 

If you are under the regular screening age or between screenings and you experience prolonged symptoms of gastrointestinal disease, see your doctor as soon as possible. The earlier cancer is detected, the more likely it is to be treated successfully.

Request an appointment at MD Anderson online or by calling 1-877-632-6789.