The times they may be a-changing. Conventional wisdom has always held that there is no inflammation seen in patients with irritable bowel syndrome (IBS). Cutting edge research has begun to find evidence of low-grade inflammation in digestive tract tissue in some IBS patients. Considered very preliminary, these results may pave the way to new and improved treatment options. Here are the things that you need to know in order to have an understanding of the role that inflammation may play in the development and maintenance of IBS.

Two Necessary Definitions

Mast cells:

Mast cells are found in tissue all over the body. They are believed to play an important role in protecting the body from pathogens -- outside agents, such as germs or viruses, that pose a threat to your health. It is thought that mast cells induce a rapid inflammatory response in response to a pathogen. It is thus not surprising that mast cells appear to be highly involved in what we commonly know as allergies.


Cytokines are proteins that are released by mast cells and other cells associated with the immune response. It is thought that after the quick inflammatory reaction triggered by mast cells, a longer lasting inflammatory process occurs due to the release of certain kinds of cytokines. Cytokines can be pro-inflammatory or anti-inflammatory.

The Possible Problem

Imagine that your body gets infected by a nasty stomach virus (gastroenteritis). Mast cells react quickly, followed by cytokines, to fight back against the infection. The release of these substances causes abdominal pain, cramping and diarrhea. In most cases, this inflammatory response is temporary. Once the body senses that the invader has been conquered, the inflammatory process closes down.

Latest research appears to point to the possibility that, in a small set of IBS patients, this inflammatory process persists after the main infection is gone. And because things are never simple with IBS, it is also entirely possible that there are some individuals who experience this chronic low-grade inflammation without ever experiencing a clear-cut case of gastroenteritis. In any case, the continued activation of mast cells, even on a very mild basis, could contribute to the motility dysfunction that characterizes IBS, particularly in terms of continued episodes of diarrhea. In addition, mast cells can be found very close to nerve cells in the intestines, perhaps contributing to ongoing pain and visceral hypersensitivity that is typical of IBS.

Potential Risk Factors

It is not clear why this continued inflammatory process would affect some people and not others. More research is needed to investigate the following possibilities:

The Bottom Line

Investigation into the role of ongoing inflammation in the development and maintenance of IBS is in a very early stage. What is known is that, in a certain small set of IBS patients, an increase in inflammatory cells has been found in the lining of the large intestine and the ileum part of the small intestine. This inflammation cannot be seen with a microscope as part of an ordinary biopsy procedure, but requires more in-depth examination. Patients whose tissue contains these increased inflammatory substances are more likely to suffer post-infectious IBS (IBS-PI) or diarrhea predominant IBS (IBS-D). Clearly, more research needs to be conducted in order to develop a clearer picture of the role of inflammation in IBS. The hope is that this improved understanding will lead to the development of new treatment options and bring about a relief from suffering.


Barbara, G., De Giorgio, R., Stangellini, V., Cremon, C. & Corinaldesi, R. “A role for inflammation in irritable bowel syndrome?" Gut 2002 51:i41-i44.

Delvaux, M. " Role of visceral sensitivity in the pathophysiology of irritable bowel syndrome". Gut 2002 51:i61-i67.

Liebregts, T., Birgit, A., Bredack, C., Roth, A., Heinzel, S., Lester, S., Downie-Doyle, S., Smith, E., Drew, P., Talley, N. & Holtmann, G. "Immune Activation in Patients With Irritable Bowel Syndrome" Gastroenterology 2007 132:913-920.

Norton, W. & Drossman, D. “Symposium Summary Report” Digestive Health Matters 2007 16:4-7.

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