Motility Dysfunction in Irritable Bowel Syndrome

Motility or the speed of the contractions of the muscles in the intestinal system can be a problem in irritable bowel syndrome (IBS). In terms of motility dysfunction in IBS, what seems to be obvious is for the most part supported by research: Colon contractions are too fast in people with diarrhea-predominant IBS (IBS-D) and too slow in people with constipation-predominant IBS (IBS-C). In addition to the obvious, this motility dysfunction seems to start as early as the small intestine. Here is what you need to know about motility, IBS, and what may be going wrong.

Motility Triggers

A variety of common factors trigger changes in motility, whether you have IBS or not:

• Eating
• Stress
• Emotional reactions
• Hormonal changes (women)

Motility Dysfunction

In general, several areas of dysfunction appear when comparing IBS patients to healthy individuals:

Constipation

• Decrease in the number of intestinal contractions
• Longer time for food to pass through the small intestine and colon (transit time)
• No difference in the time it takes the stomach to empty (gastric emptying)
• Increase in sigmoid (lower end of colon) contractions, perhaps interfering with the flow of stool
• The delay in transit time contributes to the development of small, hard to pass, stools
• Delayed transit time contributes to abdominal pain

Diarrhea

Rapid intestinal contractions

Shorter transit time for food through the small intestine and colon

No difference in gastric emptying rate

No difference in stool weight

Rapid transit time contributes to abdominal pain

Motility as a Diagnostic Tool

Now for the bad news: Nothing with IBS ever seems clear-cut. Although research has for the most part supported the above trends, there have been some inconsistencies. Since these motility differences seem to be based on common sense, it may be that the inconsistencies seen in motility research are simply due to difficulties in accurately measuring intestinal contractions. Unfortunately, this measurement difficulty and the existence of these inconsistent findings prevent the measurement of motility as being a definitive tool (biological marker) for an IBS diagnosis.

Future Research

The good news is that while motility difficulties made up a large part of early research into IBS, research has since expanded into more complex areas. It is now thought that the motility dysfunction in IBS is entwined with visceral sensitivity issues, both of which are affected by dysfunction in the complex connections between the brain (central nervous system) and the gut (enteric nervous system). As new clues as to the reasons behind the motility dysfunction seen in IBS emerge, this opens the possibilities for more effective treatment strategies.

Further Reading;

• Five Reasons Why IBS Is Not All in Your Head
• Visceral Hypersensitivity and Irritable Bowel Syndrome
• The Brain Gut Connection in Irritable Bowel Syndrome
• Inflammation and Irritable Bowel Syndrome
• Gut Bacteria and IBS

_Sources:

_{Cann, P.A., Read, N.W., Brown, C., Hobson, N. & Holdsworth, C.D. Irritable bowel syndrome: relationship of disorders in the transit of a single solid meal to symptom patterns Gut 1983 24:405-411.}

_{Jones, J., Boorman, J., Cann, P., Forbes, A., Gomborone, J., Heaton, K., Hungin, P., Kumar, D., Libby, G., Spiller, R., Read, N., Silk, D., & Whorwell, P. British Society of Gastroenterology guidelines for the management of the irritable bowel syndrome Gut 2000 47:ii1-ii19.}

_{Kellow, J. Gut Motility: In Health and Irritable Bowel Syndrome. International Foundation for Functional Gastrointestinal Disorders Fact Sheet.}

_{Lund, C. Motility disorders in the irritable bowel syndrome. Gastroenterology Clinics of North America 1991 20:279-295.}