• tanellewestgard

IBS vs IBD - what's the difference?

Updated: Sep 20, 2019

Have you ever been out talking to a group of girls and someone casually brings up that they have IB? . I put a question mark because for so long whether someone told me they had IBS or IBD I nodded my head and pretended I knew exactly what they were talking about. I also thought they were the same thing, which I now know is far from true. 

Therefore this post is about making that distinction between IBS and IBD because although they may seem similar, they are also clinically very different. 

IBS (Irritable Bowel Syndrome)

Used to be referred to as Functional bowel disorder and is referred to as a syndrome rather than a disease. It is a syndrome in which diagnosed based on symptoms (1). It is usually a diagnosis of exclusion, in which is made my a process of elimination (1). This means eliminating diseases such as IBD. In comparison to IBD, IBS has no abnormalities seen upon a scope or diagnostic markers found during blood work.

How is IBS diagnosed?

IBS is diagnosed via the Rome criteria : recurrent abdominal pain/discomfort for 1 day per week for at least the last 3 months and is associated with at least 2 of the following (2,4).

  • improvement with defecation

  • onset occurs with a change in stool frequency

  • onset occurs with a change in stool form 

  • these symptoms need to be present for at least 6 months

What are other symptoms? (1,4)

  • abdominal pain

  • diarrhea, constipation or both 

  • gas, burping, bloating

  • heartburn

  • nausea and vomiting 


The reason for IBS is poorly understood but there are a few theories on it. It has been recognized as a biopsychosocial disorder. To break this down, there are potential biological factors (inflammation and infection), psychological (anxiety, depression) and social factors (stress) involved (3,4).

IBD (Inflammatory Bowel Disease) 

IBD is a disease (rather than a syndrome like IBS) and is diagnosed based on detectable abnormalities seen on a scope and results found during blood work (5). These structural abnormalities include ulcers and lesions that involve inflammation and can be seen in the large intestine and or small intestine depending on the disease. The diagnostic markers include inflammatory as well as immune system markers (6, 7).

Within IBD there are different subtypes but the two most common include:

  • Crohn's Disease

  • Ulcerative Colitis 

These vary in how they affect the gastrointestinal system.

What are some symptoms (6,9):

Although many of these symptoms are similar to IBS, they are much more severe.

  • intermittent attacks of diarrhea (can contain blood or mucous)

  • fever

  • abdominal pain 

  • severe fatigue

  • anemia 

  • joint pain

  • weight loss

  • redness of the eyes

  • skin changes

symptoms persist for a period of time and then subside or go away (remission of symptoms)  (6).

It can take a while for people to get diagnosed with IBD due to the nature of the diagnosis. However, once diagnosed there are patients that often have to visit many doctors and try many different therapies to try and resolve their symptoms. 


The reason for IBD is also not entirely understood but the theories include a defect or alteration in our gut's immune system, an autoimmune process, infections that develop in the digestive system, and genetics (6,7,8).  Both Crohn's and Colitis produce inflammatory cells that we can identify (6,7). Interestingly, they are also associated with increased incidence of other autoimmune diseases (9).

I hope this post provided you with some insight on the difference between the two IB? . xo


1. Jones, R., & Lydeard, S. (1992). Irritable bowel syndrome in the general population. Bmj, 304(6819), 87-90.

2. Talley, N. J. (1999). Irritable bowel syndrome: definition, diagnosis and epidemiology. Best Practice & Research Clinical Gastroenterology, 13(3), 371-384.

Boucher Biomed Department Notes

3. Camilleri, M., & Choi, M. G. (1997). Irritable bowel syndrome. Alimentary pharmacology & therapeutics, 11(1), 3-15.

4. Olden, K. W. (2002). Diagnosis of irritable bowel syndrome. Gastroenterology, 122(6), 1701-1714.

5. Lewis, J. D. (2011). The utility of biomarkers in the diagnosis and therapy of inflammatory bowel disease. Gastroenterology, 140(6), 1817-1826.

6. Carter, M. J., Lobo, A. J., & Travis, S. P. (2004). Guidelines for the management of inflammatory bowel disease in adults. Gut, 53(suppl 5), v1-v16.

7. Fasano, A., & Shea-Donohue, T. (2005). Mechanisms of disease: the role of intestinal barrier function in the pathogenesis of gastrointestinal autoimmune diseases. Nature Reviews Gastroenterology & Hepatology, 2(9), 416.

8. Orholm, M., Munkholm, P., Langholz, E., Nielsen, O. H., Sφrensen, T. I., & Binder, V. (1991). Familial occurrence of inflammatory bowel disease. New England journal of medicine, 324(2), 84-88.

9. Danese, S., Semeraro, S., Papa, A., Roberto, I., Scaldaferri, F., Fedeli, G., ... & Gasbarrini, A. (2005). Extraintestinal manifestations in inflammatory bowel disease. World journal of gastroenterology, 11(46), 7227.

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