Does Mechanical Bowel Preparation Destabilise the Gut Microbiota and Provide a Window of Opportunity in Which to Influence the Re-establishing Microbiota in Diverticulosis?

The mechanical bowel preparation (BP) procedure, which directly precedes colonic endoscopy, results in a significant reduction in reported symptoms for several bowel disorders (eg irritable bowel syndrome (IBS )), but as yet, there is little research-based supporting evidence. This proposal will use a robust experimental design to explore both the composition of the microbiota, and importantly, its metabolic activity to assess interactions with human hosts following BP. The aim of this pilot study is to generate data demonstrating the destabilising effects of BP on both the composition and metabolic activity of the gut microbiota.

If the hypothesis is proven, this study will show that BP generates a 'window of opportunity' in which to influence the subsequent re-establishment of the microbiota. This is with the eventual aim of correcting dysbiosis and preventing the development of symptomatic uncomplicated diverticular disease in patients with diverticulosis.

Background Diverticular disease, characterised by weakness of the supporting connective tissue of the wall of the colon leading to the formation of diverticula1, is somewhat neglected and does not receive scientific attention that other inflammatory gut disorders have. Despite this condition affecting 50% of our aging population, approximately 1/5 of which will develop debilitating symptomatic uncomplicated diverticular disease (SUDD)2, there is a paucity of knowledge in this field.

The factors determining the transition from asymptomatic diverticulosis to SUDD are unclear. However, the gut microbiota has been implicated in a recent small-scale study which correlated diverticulosis with depletion of Clostridium cluster IV. Clostridium cluster IX, Fusobacterium and Lactobacillaceae, all of which can exert an anti-inflammatory effects. Patients who present with left-side non-specific abdominal pain and diarrhoea are assessed by colonic endoscopy. A small-scale study showed that this procedure also resulted in a significant reduction in Lactobacillaceae in the control population after 1 month (n=10).

BP is received 14 and 20 hours prior to colonoscopy and involves oral administration with a variety of stimulant laxatives (eg Moviprep - polyethylene glycol) resulting in severe diarrhoea and complete clearance of faecal matter from the bowel. It is likely that this BP is implicated in any reduction in reported symptoms as opposed to the endoscopic procedure itself, although putative underlying mechanisms have yet to be identified.