Characterising IBS subtypes and their response to Stress using MRI

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Irritable Bowel Syndrome (IBS) is an extremely common condition which causes recurrent abdominal pain and erratic bowel habits. Although not fatal it can markedly reduce the sufferer‘s quality of life. IBS sufferers report a confusing range of disturbances of bowel habit including both diarrhoea and constipation, sometimes in the same patient. Patients reported symptoms are subjective and their significance is uncertain without a reliable way of measuring bowel function. More than half the IBS patients are abnormally anxious and two thirds believe their symptoms are stress related, which may explain the day to day variability in bowel habit. However it is difficult to objectively determine the effect of stress in any individual patient. We have recently developed and validated a new, non-invasive, Magnetic Resonance Imaging (MRI) technique to image small bowel and colon function. We believe that this could be a convenient test, costing less than many currently used tests, to objectively assess IBS patients and quantify their responsiveness to stress. We believe that stress acts on the gastrointestinal system by releasing a chemical, called CRF which acts via the nervous system and special cells in the gut called mast cells. This stimulates contractions and accelerate movements through the bowel. We have recently shown that MRI can detect the effect of CRF on the small bowel whose water content is reduced by 1/3rd within 30 minutes of injection. Previous studies show that CRF also stimulates colonic contractions. We aim to develop new methods of economically and effectively analysing colon images to compliment our method of studying small bowel water content and rates of movement through the gut. We will characterise the small and colonic water content and transit rates in various subtypes of IBS patients in whom we will also assess mast cells in the colonic mucosa. We will then test our hypothesis that the bowel and its mast cells in IBS patients are more sensitive to the stress by examining the correlation between MRI parameters, mast cell activation and psychological markers of stress. Our studies will lead to a better understanding of abnormalities of gut function and the effect of stress in IBS patients. They may also provide novel ways of predicting the response of individuals to different treatments.