MRI Helps Identify and Treat Irritable Bowel Syndrome

In three separate studies, researchers examined the disorder and found another way of examining the condition, which could have major implications in how it is both diagnosed and treated in the future.

The three studies explored the effectiveness of using MRI to evaluate the colon, which has a number of novel advantages. Before this, clinicians have relied on -rays to view the colon, which has limitations due to the risks tied to radiation. By using MRI as an alternative, the researchers have been able to image the bowel continuously with no risk to the patient, enabling them to learn more about the inner workings of the gut.

The research has been led by researchers from the University of Nottingham’s (UK) Digestive Diseases Center (NDDC) and scientists from the Sir Peter Mansfield Magnetic Resonance Center at the University. In the first study, published in the January 2014 issue of the journal Neurogastroenterology and Motility, scientists were able to image the colon and split it in to three functional regions: the ascending colon, which is a storage and fermentation region, where unabsorbed residue is broken down by bacteria; the transverse colon, which is a storage area for the residue left after bacterial processing, and the descending colon, which is an organ that pushes waste down and out of the body.

Using MRI, scientists can also measure the volumes of these regions, which they have never been able to do before. Prof. Robin Spiller, lead director of Nottingham digestive diseases biomedical research unit, said, “We studied people with accelerated transit and to our surprise, we found that the colon size was rather similar to those with normal transit suggesting people regulate their bowel habit to keep the colonic size constant. We also know that when you eat a meal the ascending colon expands as the meal is pushed down into it to make space in the small bowel for the new meal. We found that this increase was smaller in IBS patients than in healthy volunteers, suggesting that the IBS patient’s ascending colon can’t relax enough. With MRI, we can actually measure this change in a way that we’ve never been able to do before. This will have other benefits in the future, for instance we will be able to measure the effect of some drugs on the bowel.”

In the second study, published in the January 2014 issue of the journal Neurogastroenterology and Motility, scientists used MRI scanning to gauge the actual time it takes for contents to transit the bowel, using specially designed MRI visible markers, which subjects ingest. Scientists can then image the bowel 24 hours later to see how far they have moved. Previously, motility had to be measured using X-rays, which has extremely limited the circumstances when the measurement could be made.

In the third study, published online November 19, 2013, in American Journal of Gastroenterology, researchers used the colonic imaging technique again, but this time, to improve their understanding of the causes of IBS. By looking at fructose, a sugar commonly found in fruit, and fructans, which are polymers of fructose, researchers were able see what effects these had on the gut of healthy study participants. “We already know that fructose is difficult to absorb, but the novelty with this new method, is that we are now able to image the end effect of this malabsorption which is the distension of the small intestine and colon. We are currently repeating these studies in patients with IBS to see whether their symptoms correlate with the distension of the colon.”

Fructans and fructose are part of a group of chemicals called FODMAPs (fermentable oligo, di- monosaccharides and polyhydric) alcohols, whose characteristics are that they are comparatively tough to absorb, but they are fermentable, so when they go in to the colon they are exposed to the bacteria and produce gas.

Prof. Spiller continued, “It’s been found that diets that restrict the intake of these things improve symptoms and our MRI studies show us scientifically why that improvement might occur. We were able to show that while fructose alone was poorly absorbed and distended the small bowel, when it was combined with glucose the poor absorption was prevented. We also found that fructans have little effect in the small bowel but a large effect on the colon. In future, will be able to use our MRI techniques to test specific foods to understand how they will affect IBS.

“By defining the link between the chemistry of food to its impact on the bowel our technique will enable us to answer specific questions, e.g., when an apple ripens and the sugar content rise, does the adverse effect reduce? This might explain why green apples can cause stomachache while ripe ones do not. The fructose in the green apple is malabsorbed but as it ripens the glucose content rises improves fructose absorption, improving the rate of absorption.”

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