Irritable bowel syndrome (IBS) is a chronic disorder of the large intestine, also known as the colon.

Because IBS and colon cancer affect the same part of the body, they share some symptoms. If you have some of these symptoms, it’s important to know the differences.

Some of the most common symptoms of IBS are changes to bowel movements, including:

Other signs and symptoms can include:

Certain foods or episodes of high stress can trigger symptoms of IBS. Even though it’s a chronic condition, these symptoms can come and go.

Females tend to have an increase in symptoms during their period.

For most people with IBS, symptoms aren’t terribly severe and can be managed with lifestyle changes. Those with severe symptoms may also require medication to manage the disorder.

Diagnosing IBS

To diagnose IBS, your doctor will want to know your medical history, including:

  • all the medications you take
  • recent infections
  • recent stressful events
  • basic diet and foods that seem to affect symptoms

Your personal and family history are also important. This includes history of:

Your doctor will do a physical exam to check for abdominal bloating and tenderness. You may not need any additional testing to get a diagnosis of IBS, but some tests can rule out other conditions. These include:

The diagnosis involves a pattern of symptoms, which includes abdominal pain and two or more of the following symptoms:

  • Abdominal pain that gets better or worse after a bowel movement.
  • Your bowel movements are more or less frequent than you’re used to.
  • There’s been a change in the appearance of your stools.

You may be told you have IBS if:

  • symptoms began at least 6 months ago
  • you’ve had problems at least once a week over the last 3 months

Symptoms of colon cancer, or colorectal cancer, may not become obvious until the cancer starts to spread. It’s a slow growing cancer, which is one reason colonoscopy screenings are so important.

During a colonoscopy, precancerous polyps can be removed before they develop into cancer.

Signs and symptoms of colon cancer can include changes to bowels and bowel habits that last for more than a few days, such as:

  • abdominal cramping or pain
  • constipation
  • dark stool or blood in stool
  • diarrhea
  • excess gas
  • fatigue
  • a feeling that bowel movements aren’t complete
  • narrowing of the stool
  • rectal bleeding
  • unexplained weight loss
  • weakness

Diagnosing colon cancer

As with IBS, your doctor will want your complete personal and family medical history.

Risk factors may include:

In addition to a physical exam, your doctor may order blood and stool tests. If cancer is suspected, other tests may include:

  • colonoscopy, along with tissue biopsy
  • imaging tests, such as X-ray or CT scan of the colon and rectum

The biopsy can confirm the presence of colon cancer and imaging tests can help assess whether the cancer has spread.

Although some symptoms of IBS and colon cancer are the same, there are some distinct differences to keep in mind. This chart shows how IBS and colon cancer are similar and how they differ.

SymptomIBSColon cancer
abdominal cramps or pain related to bowel movementsXX
changes in bowel habits lasting more than a few daysXX
constipationXX
diarrheaXX
feeling that bowel movements are incompleteXX
bloating or excess gasXX
whitish mucus in stoolX
dark stool or blood in stoolX
fatigueX
general weaknessX
narrowing of stoolX
rectal bleedingX
unexplained weight lossX

IBS, with all its discomforts and inconveniences, doesn’t cause damage to your digestive tract or lead to other health problems.

A 2010 trial found that when undergoing colonoscopy, people with IBS were no more likely to have structural abnormalities of the colon than healthy people.

They also found that people with IBS are at no greater risk of precancerous polyps or colon cancer.

Seek the advice of a doctor if you have any concerns about abdominal discomfort or changes in bowel habits. Symptoms of IBS can also indicate a variety of other conditions, including colon cancer.

Other signs that you should see a doctor right away include:

Having IBS doesn’t increase your risk of colon cancer, but that doesn’t mean you should ignore symptoms. To be on the safe side, tell your doctor about new symptoms such as rectal bleeding, narrowed stool, or weight loss.

Talk to your doctor about colon cancer screening. For most people, colonoscopy screening should begin at age 50.

If you have a family history of colon cancer or other risk factors, your doctor may recommend earlier or more frequent screening.

IBS can generally be managed by making certain dietary and other lifestyle changes. More severe cases can be treated with medications.

Having IBS doesn’t increase your risk of developing colon cancer.

Symptoms of colon cancer tend to appear only after the disease has spread. Screening for colon cancer can detect and remove precancerous polyps before they have the chance to develop into cancer.

Because the symptoms of IBS, colon cancer, and some other gastrointestinal disorders overlap, see a doctor to get the right diagnosis. They can help you manage or treat your condition so you can start feeling better.