Chronic diarrhoea is a common problem, hence clear guidance on investigations is required. This is an updated guideline from 2003 for the investigations of chronic diarrhoea commissioned by the Clinical Services and Standards Committee of the British Society of Gastroenterology (BSG). This document has undergone significant revision in content through input by 13 members of the Guideline Development Group (GDG) representing various institutions. The GRADE system was used to appraise the quality of evidence and grading of recommendations.

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The acute phase of IBD with inflamed gut and often ulcerated mucosa is clearly different from the apparently normal mucosa characteristic of IBS. However, more detailed assessment has detected immune activation, increased gut permeability, increased mucosal serotonin availability, abnormalities of enteric nerve structure and function, and dysbiosis in gut microbiota in IBS - all features seen in IBD. Furthermore, as treatments for inflammation in IBD have become more effective it is now apparent that ∼1 in 3 patients with IBD in remission from inflammation still have persistent abnormalities of sensation, motility and gut microbiota, which might cause IBS-like symptoms. This Perspective explores the overlap between IBS and IBD and their treatments, proposing future directions for research in this stimulating area.

Background & aimsIngestion of poorly digested, fermentable carbohydrates (fermentable oligo-, di-, mono-saccharides and polyols; FODMAPs) have been implicated in exacerbating intestinal symptoms and the reduction of intake with symptom alleviation. Restricting FODMAP intake is believed to relieve colonic distension by reducing colonic fermentation but this has not been previously directly assessed. We performed a randomised controlled trial comparing the effect of a low FODMAP diet combined with either maltodextrin or oligofructose on colonic contents, metabolites and microbiota.MethodsA parallel randomised controlled trial in healthy adults (n = 37). All subjects followed a low FODMAP diet for a week and supplemented their diet with either maltodextrin (MD) or oligofructose (OF) 7g twice daily. Fasted assessments performed pre- and post-diet included MRI to assess colonic volume, breath testing for hydrogen and methane, and stool collection for microbiota analysis.ResultsThe low FODMAP diet was associated with a reduction in Bifidobacterium and breath hydrogen, which was reversed by oligofructose supplementation. The difference in breath hydrogen between groups post-intervention was 27ppm (95% CI 7 to 50, P<0.01). Colonic volume increased significantly from baseline in both groups (OF increased 110ml (19.6%), 95% CI 30ml to 190ml, P = 0.01; MD increased 90ml (15.5%), 95% CI 6ml to 175ml, P = 0.04) with no significant difference between them. Colonic volumes correlated with total breath hydrogen + methane. A divergence in Clostridiales abundance was observed with increased abundance of Ruminococcaceae in the maltodextrin group, while in the oligofructose group, Lachnospiraceae decreased. Subjects in either group with high methane production also tended to have high microbial diversity, high colonic volume and greater abundance of methanogens.ConclusionA low FODMAP diet reduces total bacterial count and gas production with little effect on colonic volume.

Psyllium is a widely used treatment for constipation. It traps water in the intestine increasing stool water, easing defaecation and altering the colonic environment. We aimed to assess the impact of psyllium on faecal microbiota, whose key role in gut physiology is being increasingly recognised. We performed two randomised, placebo-controlled, double-blinded trials comparing 7 days of psyllium with a placebo (maltodextrin) in 8 healthy volunteers and 16 constipated patients respectively. We measured the patients’ gastrointestnal (GI) transit, faecal water content, short-chain fatty acid (SCFA) and the stool microbiota composition. While psyllium supplement had a small but significant effect on the microbial composition of healthy adults (increasing Veillonella and decreasing Subdoligranulum), in constipated subjects there were greater effects on the microbial composition (increased Lachnospira, Faecalibacterium, Phascolarctobacterium, Veillonella and Sutterella and decreased uncultured Coriobacteria and Christensenella) and alterations in the levels of acetate and propionate. We found several taxa to be associated with altered GI transit, SCFAs and faecal water content in these patients. Significant increases in three genera known to produce butyrate, Lachnospira, Roseburia and Faecalibacterium, correlated with increased faecal water. In summary, psyllium supplementation increased stool water and this was associated with significant changes in microbiota, most marked in constipated patients.

MRI measurements can objectively demonstrate the mode of action of therapy targeting intestinal fluid content in constipation.

This study successfully demonstrated the use of a novel MRI tagging technique to visualize and assess the motion of ascending colon contents following a 500 mL macrogol challenge. Significant differences were demonstrated between healthy and constipated subjects.

Background: Cystic fibrosis (CF) is a multi-system genetic disorder affecting > 72,0 0 0 people worldwide. Most CF patients experience gastrointestinal symptoms and can develop complications. However, the mechanisms of CF gut disease are not well understood. We evaluated gut function and transit in CF using magnetic resonance imaging (MRI). We hypothesised oro-caecal transit time (OCTT) is longer in CF; with lower small bowel water content (SBWC).Methods: Twelve CF patients aged 12-40 years and 12 age and sex-matched controls underwent serial MRIs over 1 day with standardised meals. The primary endpoint was OCTT, assessed by the appearance of a food bolus in the caecum. Other measures included corrected SBWC and corrected colonic volume (both area under the curve, AUC), gastric half-emptying time and gastrointestinal symptoms.Results: OCTT was longer in CF (CF 330 mins [270, > 360] vs. controls 210 mins [173, 315], p = 0.04), with no difference in gastric half-emptying times. Corrected SBWC was higher in CF (CF 62 L.min/m 2 [36, 80] vs. controls 34 L.min/m 2 [28, 41], p = 0.021); minimal postprandial decrease between T240 and T300 (CF 13 mL/m 2 [-13, 57] vs. controls 102 mL/m 2 [67, 108], p = 0.002) suggests impaired ileal emptying. Corrected colonic volumes were higher in CF (CF 186 L.min/m 2 [167, 206] vs. controls 123 L.min/m 2 [89, 146], p = 0.012). There were no differences in gastrointestinal symptoms.Conclusions: MRI provides novel insights into CF pathophysiology. Sub-clinical ileal obstruction may be more prevalent than previously thought. Gastrointestinal MRI shows promise as an investigational tool in CF.