The Role of Inflammation in Irritable Bowel Syndrome

Conventional wisdom has always held that inflammation not seen in patients with irritable bowel syndrome (IBS). Well, the times they may be a-changing.

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. Because of this, there are a few things you'll want to know about the role that inflammation may play in the development and maintenance of IBS.

Woman lying on couch with stomach cramps
Laylabird / Getty Images

Defining Two Key Factors

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 to a pathogen. Therefore, it is not surprising that mast cells appear to be highly involved in what we commonly know as allergies.

Cytokines. 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

In order to visualize the inflammatory response, 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.

Some 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. Things are rarely 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. This may contribute to the 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

The 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 number 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 sharper 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 relief from suffering.

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By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.