When Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) Overlap or Coexist

Although inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) have similar acronyms and some similar symptoms, they are very different gastrointestinal disorders. The different forms of IBD, such as Crohn’s disease and ulcerative colitis, cause visible inflammation and other structural changes in the digestive tract, as well as tangible biomarkers in one’s blood that can be measured by existing tests. As such, IBD is traditionally classified by the medical profession as an “organic” disorder.  Meanwhile, IBS, in which no structural differences from a “normal” colon or biomarkers can be obviously seen through existing tests and procedures currently available to physicians in a clinical setting, is considered a “functional” disorder.

In addition, IBS is considerably more common than IBD. Some of the demographic groups that are at higher risk for each disorder are different. Treatments used for IBD generally do not work for and are not accepted medical protocol for IBS and vice versa. Anecdotally, community resources, such as support groups, tend to be more readily available for IBD than IBS. Some people may be diagnosed with both IBS and IBD, but one condition does not cause the other. In fact, one of the frequent challenges of both the IBS and IBD communities is making the media and general public– including sometimes our own IBS and/or IBD affected peers and families– aware that IBS and IBD are not different names for the same condition. Three years ago, this blog published a post about the differences. Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) Are Not the Same.

The basic differences outlined in that post and the associated linked resources are still valid, and as far as leading international researchers in gastroenterology currently understand the science, IBD and IBS are still separate disorders. But like much related to irritable bowel syndrome, the reality is much too complex to reduce to simple media sound bites or Internet memes. As mentioned in IBS Impact’s 2011 post on the subject, for some time, researchers had already recognized that some people with irritable bowel syndrome do have subtle inflammation, especially in the post infectious-IBS (IBS-PI) subset, and anti-inflammatories, including some medications traditionally prescribed for IBD, have been tested in clinical trials for IBS, before and since that post, with mixed results. Over many years, various academic researchers of functional gastrointestinal disorders like IBS have also found evidence of neurological changes in pain perception, dysfunction in neurotransmitters and the brain-gut axis, altered gut microflora, genetic changes, and changes in immune mediators, though at a lower level than in IBD, in various subsets of people with IBS. So although numerous pieces of the puzzle that is irritable bowel syndrome remain to be put together, it is increasingly clear that IBS is not just a disorder of function.

Conversely, IBD may not be as straightforward as traditionally assumed either, as is seen in the subset of people who have coexisting diagnoses of inflammatory bowel disease and irritable bowel syndrome. According to Douglas Drossman, MD, MACG, founder and co-director emeritus of the University of North Carolina Center for Functional GI and Motility Disorders,  founder and president of the Rome Foundation, and founder and president of the Drossman Center for the Education and Practice of Psychosocial Care, this group of people is now said by medical professionals to have what is called IBS-IBD. In his September 13, 2014 blog post, Understand IBS-IBD From the Biopsychosocial Perspective, Dr. Drossman writes that is now possible for IBD medications to resolve observable gastrointestinal inflammation to such microscopic levels that IBD is considered in remission. Yet, up to 20% of these people continue to experience significant pain and diarrhea similar to IBS-D. Interestingly, in  the past several years, researchers have observed that the way IBS-IBD presents is very similar to postinfectious IBS.

International experts in IBS like Dr. Drossman have long advocated a comprehensive biopsychosocial approach to treating IBS, in recognition of the influence psychological stress and cognitive beliefs can have on the physical aspects of IBS and vice versa. In the linked post, he explains its importance for the specific IBS-IBD subset as well.

The IBS-IBD subset of people with IBS is rarely, if ever, mentioned in educational material readily available to people with IBS, families and the media or general public.  IBS Impact thanks Dr. Drossman for his continuing leadership in the field and for bringing these aspects to wider attention through his post. It is hoped that in the future, further research in general and with the IBS-IBD group in particular will yield useful insights into the causes and treatment of both IBD and IBS.

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