Symptoms of irritable bowel syndrome in patients with inflammatory bowel disease

• Main Author: Berrill, James
• Published: Cardiff University 2014
• Subjects: 616.3; Q Science (General)
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611064

Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are both chronic relapsing intestinal disorders. Their symptom profiles overlap in terms of abdominal discomfort and altered bowel habit. Meta-­‐analysis of patients with IBD demonstrates that 25-­‐46% of those in clinical remission have symptoms compatible with IBS. These patients report lower quality of life scores compared to their asymptomatic counterparts. There is uncertainty as to the cause of these symptoms, and concern for the influence they may exert on clinical management. The work described in this thesis investigated the nature of IBS-­‐type symptoms occurring in patients with IBD, examined potential diagnostic tools to distinguish between the respective conditions, and conducted a therapeutic trial for the management of functional symptoms in this setting. IBS-­‐type symptoms were observed to occur more commonly in female IBD patients, were associated with high anxiety levels, and occurred in patients with no active inflammation as confirmed by a normal faecal calprotectin level. These findings are characteristic of irritable bowel syndrome, and suggest that this disorder may cause persistent symptoms during IBD remission. Two potential biomarkers of IBS were investigated. The first explored a hypothesis that IBS may be a systemic condition caused by the absorption of toxic metabolites produced by the bacterial fermentation of dietary carbohydrates. This mechanism would potentially explain both the gastrointestinal and the systemic symptoms that are observed in patients with IBS. It was proposed that toxic metabolites may covalently modify albumin in patients with IBS, however on investigation of this theory there was no significant difference observed between the plasma samples of IBS patients, IBD patients and healthy controls. The presence of systemic symptoms in patients with IBS and IBD was associated with higher anxiety levels. Cognitive function was also assessed as a potential biomarker of IBS following anecdotal reports that IBS patients experience impaired concentration. However no significant difference between IBS patients, IBD patients, and healthy controls was identified. Concurrent mood disorders, in particular depression, were associated with impaired performance of specific tasks in patients with IBD. A randomised-­‐controlled trial of a mindfulness-­‐based psychological intervention was performed in IBD patients with IBS-­‐type symptoms or high perceived stress levels. Sub-­‐group analysis demonstrated a significant improvement in quality of life in the intervention group in those patients who were experiencing IBS-­‐type symptoms. Overall, these findings support the theory that IBS can cause persistent symptoms in IBD patients who are in remission. However, until the molecular mechanisms underlying IBS are identified and reliable biomarkers are developed, a systematic diagnostic approach is required to evaluate these patients. IBS-­‐type symptoms in IBD patients represent a therapeutic target to improve quality of life and further trials of psychological intervention, medication and dietary modification are required.