Assessing the Effect of Lettuce on Intestinal Water Content Through Magnetic Resonance Imaging of the Small Bowel

Overview

When patients have bowel surgery they are sometimes left with a stoma, where the small bowel exits onto the wall of the abdomen, not into the colon. Certain foods have been shown to increase the amount of water lost through a stoma. This can lead to dehydration. Such patients are encouraged to avoid such foods but knowing which ones to avoid relies partly on trial and error. In a survey 1 in 3 patients said that rhubarb increased stoma output. Rhubarb is known to contain chemicals that can stimulate the bowel. 1 in 6 patients also reported the same effect with lettuce which has not previously been shown to have such an effect. Latex found in lettuce leaves may stimulate the bowel to produce more fluid, explaining this effect. In Nottingham the investigators have developed techniques that use Magnetic Resonance Imaging (MRI) to measure water in the small bowel. They want to use these techniques to explore whether eating lettuce increase small bowel water content. They will compare lettuce to rhubarb and to bread, which they know reduces small bowel water. They will see if they can detect any relationship between water in the bowel and feelings of bloating.

Background: In recent years fermentable oligo-, di-, mono-saccharides and polyols, have been proposed to exacerbate symptoms of irritable bowel syndrome (IBS) such as abdominal discomfort and bloating. This phenomenon has also been observed in patients with an ileostomy, where certain foods have been associated with increased fluid output from the stoma. This is in accordance with past work surveying ileostomy patients on foods that altered stoma function. However, there may be other factors that drive fluid output from a stoma. Rhubarb, a food listed by 1 in 3 patients as exacerbating watery diarrhoea, also contains anthraquinones that have laxative effects, such as in senna. A food less commonly associated with laxative effects is lettuce but 1 in 6 patients reported that eating lettuce led to an increase in watery stoma output. Certain lettuce varieties exude a milk-like latex material when cut, giving rise to the latin name Lactuca sativa. While the methylcellulose is insoluble and would not be expected to hold water in the lumen of the small bowel, latex could be expected to stimulate intestinal secretion. This may contribute to post-prandial sensations of bloating by a different mechanism to the osmotic effects and colonic fermentation seen with poorly absorbed but fermentable carbohydrates.. The Nottingham GI MRI group has been at the forefront of elucidating the effects of poorly digested carbohydrates on gastrointestinal physiology. the investigators have published techniques to measure free water in the small bowel and assessment of viscosity in the colon using MR relaxometry. This includes the demonstration that fructose ingestion on its own leads to increased free water in the small bowel compared to co-ingestion with glucose - see panel. The investigators wish to apply these techniques to compare the effect of different foods: white bread, lettuce and rhubarb. The investigators have previously shown that bread led to a reduction in small bowel water and so can active as a negative control. Rhubarb should serve as a positive control. Aims: The purpose of the study is gather pilot data on the effect of different foods on intestinal physiology.