How IBS Differs From Other Conditions

ven diagram with IBS and IBD

Amber J Tresca

Irritable bowel syndrome (IBS) is a disease of exclusion, meaning that a diagnosis of IBS is often given after no other cause for the symptoms can be found. This also means that IBS is frequently misdiagnosed, and treated, as other conditions. Some people may see several different doctors and undergo many tests before finally arriving at a diagnosis of IBS.

There is some research that indicates there are genes associated with IBS, making IBS potentially inheritable. Some of those genes have been found, though it's still unclear how much a person's genes affect their risk of having this condition.

What are the other conditions that have symptoms similar to IBS? These conditions are known as “differential diagnoses”—different conditions that have a similar set of symptoms or “presentation.”

Inflammatory Bowel Disease (IBD)

IBS is often confused with ulcerative colitis or Crohn's disease, which collectively known as IBD. But there are significant differences. IBS is a syndrome, not a disease, and it will not lead to colon cancer, nor does it cause inflammation or intestinal bleeding. IBD will often cause inflammation or ulcers in the intestinal wall that can be seen by a physician during a colonoscopy, while IBS does not cause any of these physical signs. IBD can also cause severe abdominal pain, fevers, and weight loss, which are not seen with IBS.

It is possible for people who have IBD to also have IBS. However, there is an important distinction to make: having IBS does not mean it is going to "progress" or "turn into" IBD. IBS is not a progressive disease, and it does not actually cause any damage to the intestines or other parts of the digestive tract.

People with IBD may need surgery as a treatment for their disease. Surgery is not performed to treat IBS. In addition, IBD often affects other parts of the body outside the digestive tract. 

Key Points: IBS does not cause inflammation, ulcers, bleeding, or significant weight loss.

Celiac Disease

Celiac disease (what used to be called celiac sprue) is reportedly underdiagnosed because many people still think that this is a rare childhood disease. In fact, as many as 1 in 100 people may have this hereditary condition, according to the Celiac Disease Foundation, though some experts put that figure even higher. While it is not the same as IBS, it is estimated that celiac disease is four times more common in those with IBS symptoms than those without those symptoms. 

It may take years to get a diagnosis of celiac disease, as the symptoms are often vague and may be overlooked or assumed to be caused by other conditions.

When a person with celiac disease eats gluten (a common food ingredient), an immune response is triggered that causes damage to the lining of the small intestine. This results in the small intestine being unable to absorb critical nutrients. Unlike IBS, for which there is no diagnostic test, celiac disease can be diagnosed with 85% to 98% accuracy with antibody tests (the most recent and accurate tests are for the anti-deamidated gliadin peptide, or DGP, antibody, and for the anti-tissue transglutaminase, or anti-tTG, antibody). It can also be excluded as a possible diagnosis with more than 99% accuracy with genetic testing for the HLA-DQ2 and HLA-DQ8 genes.

The basis for the treatment of celiac disease is the elimination of gluten from the diet.

Key Points: Celiac disease can often be accurately diagnosed with antibody tests or genetic testing, and symptoms often improve rapidly with a gluten-free diet.

Infection

A viral, parasitic, or bacterial infection can cause the symptoms common in IBS such as abdominal pain, bloating, and diarrhea. These infections may be the common “stomach flu” (viral gastroenteritis), food poisoning, or from water contaminated with harmful parasites. These types of infections tend to be acute rather than chronic; the symptoms start quickly and may be severe. In many cases, there may be a clear event that precipitated the symptoms, such as eating undercooked food (in the case of food poisoning) or having contact with a person with similar symptoms (such as with the stomach flu).

While these infections are not the same as IBS, IBS can in fact develop after a bacterial infection. The mechanism by which this occurs is not yet well understood.

Key Points: Bacterial and parasitic infections often improve after treatment with antibiotics, and viral infections tend to improve after a few days. However, symptoms of IBS are chronic.

A Word From Verywell

IBS is often confused with other conditions, most notably IBD. In addition, the conditions are sometimes referred to by incorrect terms such as "irritated bowel disease" or "inflammatory bowel syndrome," which causes further complications and misunderstanding. When receiving a diagnosis from a gastroenterologist or other health care professional, the best idea is to get clear information and ask questions until you're comfortable with the new terms. Taking a few minutes to understand IBS is important to help clear up any questions and get on the path to the right treatment.

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Article Sources

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