Colon Cancer Versus Irritable Bowel Syndrome (IBS): What Are the Symptoms?

Colon cancer and IBS are common health problems that share some symptoms, such as excessive gas, constipation, and abdominal pain. Because there is often overlap in symptoms, it can be hard to know whether you’re dealing with colon cancer or IBS. The good news is that you’re not alone. Gastroenterologists have specialized training in the digestive system and can create a plan for managing your digestive symptoms.

What Is Colon Cancer?

Colon cancer is the short term for colorectal cancer. It happens when cells in the colon or rectum grow out of control. Your colon and rectum are part of your digestive system. The colon is the first and longest part of your large intestine. The role of your colon is to absorb water and nutrients from foods. The leftover material becomes stool (poop). The rectum is the lower part of your large intestine where your body stores stool. Sometimes abnormal growths called polyps develop in the colon or rectum. Some polyps turn into cancer over time. Other polyps never turn into cancer.

The best way to prevent colon cancer is to remove polyps before they ever have a chance to turn into cancer. That’s why it’s important to have colon cancer screening tests such as a stool-based test or colonoscopy. The American Cancer Society estimates that 106,590 new cases of colon cancer and 46,220 new cases of rectal cancer will be diagnosed in 2024.

“Irritable bowel syndrome does not increase your risk of colon cancer,” says David Palange, DO, a colon and rectal surgeon at ChristianaCare’s Helen F. Graham Cancer Center and Research Institute in Newark, Delaware. “The best ways to minimize your risk are to get colon and rectal cancer screening in concordance with national guidelines, avoid smoking, maintain a healthy weight and avoid obesity, be physically active, and limit alcohol and red meat.”

What Is IBS?

IBS is a group of symptoms that occur together, including recurrent pain in the abdomen and changes in bowel movements, which may include diarrhea, constipation, or both. With IBS, there can be symptoms without any visible signs of damage or disease in your digestive tract. IBS is considered a functional gastrointestinal (GI) disorder. Functional GI disorders are related to problems with how the brain and the gut work together. Today, doctors often talk about functional GI disorders as disorders of gut-brain interactions.

“In people with IBS, the gut receptors become sensitized — so sensitive that they feel things that most normal people don't feel,” says Satish Rao, MD, PhD, the J. Harold Harrison, MD, Distinguished University Chair in Gastroenterology at Augusta University in Georgia. “Signals from the gut are constantly being sent to the brain, but the signaling is distorted such that patients with IBS have much more intense [digestive] symptoms.” This gut hypersensitivity is a sign of IBS.

According to the American College of Gastroenterology, 10 to 15 percent of adults in the United States suffer from IBS symptoms, but only 5 to 7 percent of adults have been formally diagnosed with IBS.

Why Do Colon Cancer and IBS Get Mistaken for Each Other?

“IBS is sometimes called the greatest mimic of any GI condition because it can have similar symptoms to colon cancer, but also similar symptoms to other disorders like diverticular disease or small bowel dysfunction,” says Dr. Rao.

To help determine whether a patient has colon cancer or IBS, a gastroenterologist will take an excellent health history and listen to the patient’s main complaints. Depending on the patient’s age and symptoms, a colonoscopy and a physical exam of the rectum may be done to assess colon or rectal cancer.

If IBS is suspected based on the person’s symptoms and health history, blood and stool tests may be used to make a diagnosis. Notably, a colonoscopy is very helpful for diagnosing colon cancer, but not always necessary for diagnosing IBS.

Overlapping and unique symptoms for colon cancer and IBS can be seen in the table below.

Other symptoms, including anxiety, depression, indigestion, mucus in the stool, bathroom urgency, and food intolerance can occur in both IBS and colon cancer, but on their own these symptoms will not point to colon cancer.

Prevention

You can reduce your risk of colon cancer by getting screenings starting at age 45 and making lifestyle changes (quit smoking, maintain a healthy weight, and limit alcohol).

It is not clear what causes IBS. Lifestyle changes such as regular physical activity, adequate sleep, and increased fiber intake may reduce IBS symptoms in some people.

Treatment

Treatment for colon cancer depends on the stage of the cancer and its location. Staging has to do with the size of a tumor and whether the cancer has spread to other parts of the body. In general, the lower the stage, the less the cancer has spread. Treatments for colon cancer may include surgery, chemotherapy, local ablation, systemic therapy, and immunotherapy.

Treatment for IBS depends on whether the patient has IBS with diarrhea or IBS with constipation, but dietary measures are usually the first line of therapy. There are some medications and supplements that treat symptoms, too. If a patient with IBS has abdominal pain, a doctor may prescribe antispasmodics to relieve muscle spasms. Additionally, antidepressants are sometimes prescribed for abdominal pain because they help the brain block pain messages.

“For the management of IBS, we need to identify triggers to symptoms which would include diet and lifestyle modification, the use of probiotics and other medicines, as well as a focus on the patient’s mental health,” says Dr. Palange.

Summary

Colon cancer and IBS can be scary, but there’s hope. Both conditions can be managed in partnership with your healthcare team. Seek out medical attention right away if you experience digestive symptoms that persist beyond an expected amount of time.