Intestinal motility in irritable bowel syndrome: is IBS a motility disorder? Part 1. Definition of IBS and colonic motility

Innovative concepts in diet therapies in disorders of gut-brain interaction

Diet therapy in disorders of gut-brain interaction (DGBI) is rapidly advancing, with accumulating evidence to support two innovative therapies-manipulation of dietary fibers and enzyme supplementation-that target specific DGBI pathophysiology and modulate digestion. Dietary fibers escape digestion in the upper gastrointestinal tract and can influence gut function by impacting digestion, improving laxation, and interacting with the microbiota. A more nuanced understanding of different fiber types and their ability to impact gut function in highly specific ways has shown that fibers can impact distinct gut symptoms and pathophysiology. By considering their functional characteristics of bulking, gel-forming, and fermentability, restriction or supplementation of specific fibers can offer clinical value in DGBI. Similarly to fiber specificity, emerging evidence suggests that supplemental digestive enzymes may be targeted to known food triggers with consideration that enzymes are substrate specific. Limited evidence supports use of lactase to target lactose, and α-galactosidase to target galacto-oligosaccharides. Application of enzymes during manufacturing of food products may prove to be an additional strategy, although evidence is scant. Both innovative therapies may be utilized in isolation or in combination with other diet and nondiet therapies. Implementation can be guided by the principles that fiber modulation can be targeted to specific symptomology or requirement for alterations to gut function, and digestive enzymes can be targeted to known food triggers. This review aims to summarize recent literature of these two innovative concepts and provide practical suggestions for their implementation in clinical practice.

Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is one of the most common disorders of gut-brain interaction, with a complex pathophysiology. Antispasmodics are prescribed as first-line therapy because of their action on gut dysmotility. In this regard, peppermint oil also has antispasmodic properties.

AIM

To update our previous meta-analysis to assess efficacy and safety of peppermint oil, particularly as recent studies have cast doubt on its role in the treatment of IBS METHODS: We searched the medical literature up to 2nd April 2022 to identify randomised controlled trials (RCTs) of peppermint oil in IBS. Efficacy and safety were judged using dichotomous assessments of effect on global IBS symptoms or abdominal pain, and occurrence of any adverse event or of gastro-oesophageal reflux. Data were pooled using a random effects model, with efficacy and safety reported as pooled relative risks (RRs) with 95% confidence intervals (CIs).

RESULTS

We identified 10 eligible RCTs (1030 patients). Peppermint oil was more efficacious than placebo for global IBS symptoms (RR of not improving = 0.65; 95% CI 0.43-0.98, number needed to treat [NNT] = 4; 95% CI 2.5-71), and abdominal pain (RR of abdominal pain not improving = 0.76; 95% CI 0.62-0.93, NNT = 7; 95% CI 4-24). Adverse event rates were significantly higher with peppermint oil (RR of any adverse event = 1.57; 95% CI 1.04-2.37).

CONCLUSIONS

Peppermint oil was superior to placebo for the treatment of IBS, but adverse events were more frequent, and quality of evidence was very low. Adequately powered RCTs of peppermint oil as first-line treatment for IBS are needed.

Bacterial modulation of visceral sensation: mediators and mechanisms

The potential role of the intestinal microbiota in modulating visceral pain has received increasing attention during recent years. This has led to the identification of signaling pathways that have been implicated in communication between gut bacteria and peripheral pain pathways. In addition to the well-characterized impact of the microbiota on the immune system, which in turn affects nociceptor excitability, bacteria can modulate visceral afferent pathways by effects on enterocytes, enteroendocrine cells, and the neurons themselves. Proteases produced by bacteria, or by host cells in response to bacteria, can increase or decrease the excitability of nociceptive dorsal root ganglion (DRG) neurons depending on the receptor activated. Short-chain fatty acids generated by colonic bacteria are involved in gut-brain communication, and intracolonic short-chain fatty acids have pronociceptive effects in rodents but may be antinociceptive in humans. Gut bacteria modulate the synthesis and release of enteroendocrine cell mediators, including serotonin and glucagon-like peptide-1, which activate extrinsic afferent neurons. Deciphering the complex interactions between visceral afferent neurons and the gut microbiota may lead to the development of improved probiotic therapies for visceral pain.

Endocrine regulation of gut function - a role for glucagon-like peptide-1 in the pathophysiology of irritable bowel syndrome

NEW FINDINGS

What is the topic of this review? Pathophysiological changes linked to irritable bowel syndrome (IBS) include stress and immune activation, changes in gastrointestinal microbial and bile acid profiles and sensitization of extrinsic and intrinsic gut neurons. This review explores the potential role for L-cells in these pathophysiological changes. What advances does it highlight? L-cells, which secrete glucagon-like peptide-1 in response to nutrients, microbial factors, bile acids and short-chain fatty acids, may sense IBS-related changes in the luminal environment. Glucagon-like peptide-1 can act as a hormone, a paracrine factor or a neuromodulatory factor and, through its actions on central or peripheral neurons, may play a role in gastrointestinal dysfunction.

ABSTRACT

The prevalent and debilitating functional bowel disorder, irritable bowel syndrome (IBS), is characterized by symptoms that include abdominal pain, bloating, diarrhoea and/or constipation. The heterogeneity of IBS underscores a complex multifactorial pathophysiology, which is not completely understood but involves dysfunction of the bi-directional signalling axis between the brain and the gut. This axis incorporates efferent and afferent branches of the autonomic nervous system, circulating endocrine hormones and immune factors, local paracrine and neurocrine factors and microbial metabolites. L-cells, which are electrically excitable biosensors embedded in the gastrointestinal epithelium, secrete glucagon-like peptide-1 (GLP-1) in response to nutrients in the small intestine. However, they appear to function in a different manner more distally in the gastrointestinal tract, where they are activated by luminal factors including short-chain fatty acids, bile acids and microbial metabolic products, all of which are altered in IBS patients. Glucagon-like peptide-1 can also interact with the hypothalamic-pituitary-adrenal stress axis and the immune system, both of which are activated in IBS. Given that a GLP-1 mimetic has been found to alleviate acute pain symptoms in IBS patients, GLP-1 might be important in the manifestation of IBS symptoms. This review assesses the current knowledge about the role of GLP-1 in IBS pathophysiology and its potential role as a signal transducer in the microbiome-gut-brain signalling axis.

Neuroimmune Cross Talk in the Gut. Neuroendocrine and neuroimmune pathways contribute to the pathophysiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder characterized by recurrent abdominal pain, bloating, and disturbed bowel habit, symptoms that impact the quality of life of sufferers. The pathophysiological changes underlying this multifactorial condition are complex and include increased sensitivity to luminal and mucosal factors, resulting in altered colonic transit and visceral pain. Moreover, dysfunctional communication in the bidirectional signaling axis between the brain and the gut, which involves efferent and afferent branches of the peripheral nervous system, circulating endocrine hormones, and local paracrine and neurocrine factors, including immune and perhaps even microbial signaling molecules, has a role to play in this disorder. This minireview will examine recent advances in our understanding of the pathophysiology of IBS and assess how cross talk between hormones, immune, and microbe-derived factors and their neuromodulatory effects on peripheral nerves may underlie IBS symptomatology.

THE INTESTINAL MICROBIOTA AND THE ROLE OF PROBIOTICS IN IRRITABLE BOWEL SYNDROME: a review

Irritable bowel syndrome is a common, chronic relapsing gastrointestinal disorder that affects 7%-22% of the population worldwide. According to Rome III Criteria, the disorder is defined by the coexistence of abdominal discomfort or pain associated with an alteration in bowel habits. Its pathophysiology is not completely understood but, in addition to some important abnormalities, the disturbed intestinal microbiota has also been described supported by several strands of evidence. The treatment of irritable bowel syndrome is based upon several therapeutic approaches but few have been successful or without adverse events and more recently the gut microbiota and the use of probiotics have emerged as a factor to be considered. Probiotics are live micro-organisms which when consumed in adequate amounts confer a health benefit to the host, such as Lactic bacteria among others. An important scientific rationale has emerged for the use of probiotics in irritable bowel syndrome, although the data regarding different species are still limited. Not all probiotics are beneficial: it is important to select the specific strain which should be supported by good evidence base. The mechanisms of action of probiotics are described and the main strains are quoted.

Beliefs about management of irritable bowel syndrome in primary care: cross-sectional survey in one locality

Aim

To examine beliefs about irritable bowel syndrome (IBS) management among primary care physicians.

Background

There have been considerable advances in evidence synthesis concerning management of IBS in the last five years, with guidelines for its management in primary care published by the National Institute for Health and Care Excellence (NICE).

Methods

This was a cross-sectional web-based questionnaire survey of 275 primary care physicians. We emailed a link to a SurveyMonkey questionnaire, containing 18 items, to all eligible primary care physicians registered with three clinical commissioning groups in Leeds, UK. Participants were given one month to respond, with a reminder sent out after two weeks.

Findings

One-hundred and two (37.1%) primary care physicians responded. Among responders, 70% believed IBS was a diagnosis of exclusion, and >80% checked coeliac serology often or always in suspected IBS. Between >50% and >70% believed soluble fibre, antispasmodics, peppermint oil, and psychological therapies were potentially efficacious therapies. The respondents were less convinced that antidepressants or probiotics were effective. Despite perceived efficacy of psychological therapies, 80% stated these were not easily available. Levels of use of soluble fibre, antispasmodics, and peppermint oil were in the range of 40% to >50%. Most primary care physicians obtained up-to-date evidence about IBS management from NICE guidelines. Most primary care physicians still believe IBS is a diagnosis of exclusion, and many are reluctant to use antidepressants or probiotics to treat IBS. More research studies addressing diagnosis and treatment of IBS based in primary are required.

Increased prevalence of autoimmune diseases in functional gastrointestinal disorders: case-control study of 23471 primary care patients

BACKGROUND

There is increasing evidence that impaired mucosal defence mechanisms are implicated in the pathogenesis of the functional gastrointestinal disorders (FGIDs), allowing inappropriate immune activation.

AIM

To test the hypothesis that an excess of autoimmune disorders among sufferers, using a large primary care database to examine this.

METHODS

Cases were diagnosed with FGIDs - irritable bowel syndrome (IBS), functional dyspepsia (FD), chronic idiopathic constipation (CIC), and multiple FGIDs. Controls were those without FGIDs. Prevalence of autoimmune disorders was compared between cases and controls using odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

We included 23,471 patients (mean age 51.4 years, 66.1% female). Prevalence of autoimmune disorders was greater among all FGIDs, compared with controls without. In those with FD (OR 1.35; 95% CI 1.12-1.63), CIC (OR 1.75; 95% CI 1.11-2.75), or multiple FGIDs (OR 1.49; 95% CI 1.25-1.77) this was statistically significant after controlling for age and gender. Rheumatological autoimmune disorders were significantly more frequent in those with FD (OR 1.44; 95% CI 1.15-1.80), CIC (OR 1.84; 95% CI 1.08-3.13), or multiple FGIDs (OR 1.53; 95% CI 1.24-1.88), after controlling for age and gender. However, endocrine autoimmune disorders were no more frequent in those with FGIDs, after controlling for age and gender.

CONCLUSIONS

In a large sample of primary care patients, there was a significantly higher prevalence of autoimmune disorders among those with FD, CIC, or multiple FGIDs not explained by differences in age or gender. We were unable to control for concomitant drug use, which may partly explain this association.

Abdominal bloating: pathophysiology and treatment

Abdominal bloating is a very common and troublesome symptom of all ages, but it has not been fully understood to date. Bloating is usually associated with functional gastrointestinal disorders or organic diseases, but it may also appear alone. The pathophysiology of bloating remains ambiguous, although some evidences support the potential mechanisms, including gut hypersensitivity, impaired gas handling, altered gut microbiota, and abnormal abdominal-phrenic reflexes. Owing to the insufficient understanding of these mechanisms, the available therapeutic options are limited. However, medical treatment with some prokinetics, rifaximin, lubiprostone and linaclotide could be considered in the treatment of bloating. In addition, dietary intervention is important in relieving symptom in patients with bloating.

Antibiotics for irritable bowel syndrome: rationale and current evidence

Irritable bowel syndrome (IBS) is the most common gastrointestinal condition effecting adults in developed countries worldwide. Over the last decade, evidence has emerged suggesting that gut bacteria play a role in the pathophysiology of IBS. While difficult to identify using noninvasive means, one of the most common attributable bacterial concepts in IBS is the small intestinal bacterial overgrowth hypothesis (SIBO). In this article, we review the different mechanisms by which gut flora and, specifically, SIBO may contribute to IBS and the evidence supporting the use of various antibiotic therapies in treating IBS.

Probiotics in the management of functional bowel disorders: promise fulfilled?

Irritable bowel syndrome (IBS) and chronic constipation (CC) are common problems worldwide and are associated with significant impact on activities of daily living and quality of life. Recent interest, in IBS in particular, has focused on the potential roles of the microbiota and its interaction with the host's immune system. Recently, high-quality clinical trials have been performed on prebiotics and probiotics in IBS or CC. Although strategies that seek to modify the microbiota, such as the use of probiotics, offer much promise in IBS and CC, more high-quality trials and, studies of longer duration are required.

Effects on gastrointestinal transit and antroduodenojejunal manometry after gut-directed hypnotherapy in irritable bowel syndrome (IBS)

BACKGROUND

Gut-directed hypnotherapy is an effective treatment in irritable bowel syndrome (IBS) but little is known about the mechanisms of action. In this study we aimed to investigate the effects on gastrointestinal motility when treating IBS with gut-directed hypnotherapy.

METHODS

We randomized 90 patients with IBS, refractory to standard management to receive gut-directed hypnotherapy 1 h/week for 12 weeks or supportive treatment for the same time period. Eighty-one subjects (40 hypnotherapy, 41 controls) could be evaluated by one or more of the following investigations, both before and after the intervention: gastric emptying time, small bowel transit time, colonic transit time, and antroduodenojejunal manometry.

RESULTS

No significant differences in gastric emptying time, small bowel transit time, or colonic transit time was found when comparing the baseline and post-intervention measurements in the hypnotherapy group or in the control group. The same was true concerning the results of the antroduodenojejunal manometry. However, there was a numerical trend toward a higher number of migrating motor complexes at manometry and an accelerated gastric emptying time after hypnotherapy that did not reach statistical significance.

CONCLUSIONS

In this study, we were not able to find evidence for long-standing effects on gastrointestinal motility as a mediator of the effects on IBS when treating the condition with gut-directed hypnotherapy. Further research to understand the mechanism of action is needed.

Bugs on the brain; brain in the gut--seeking explanations for common gastrointestinal symptoms

INTRODUCTION

Gastrointestinal symptoms such as heartburn, indigestion (or dyspepsia), bloating, distension, constipation, abdominal pain, abdominal discomfort and diarrhoea are extremely common worldwide. For some, such symptoms can prove to be chronic and disabling.

METHODS

The recent literature on irritable bowel syndrome and, in particular, work emanating form this authors research group, was reviewed.

RESULTS

These functional symptoms commonly occur in aggregations, referred to as functional gastrointestinal disorders (FGIDs). Some of the FGIDs and, most notably irritable bowel syndrome (IBS), have achieved a degree of scientific and clinical credibility as coherent entities. Several lines of evidence ranging from gut motility to the microbiota are under investigation in attempts to explain IBS or its symptomatology.

CONCLUSION

Though biomarkers for IBS and other FGIDs have proven elusive, considerable progress has been made in understanding possible aetiological factors in IBS; progress which may well lead to better therapeutic strategies.

The efficacy and safety of rifaximin for the irritable bowel syndrome: a systematic review and meta-analysis

OBJECTIVES

Irritable bowel syndrome (IBS) affects 10-15% of the population, and treatment options are limited. Rifaximin is a minimally absorbed antibiotic that has shown efficacy in IBS patients. The objective of our study was to perform a meta-analysis and systematic review of available randomized, placebo controlled trials evaluating the efficacy and tolerability of rifaximin in patients with IBS.

METHODS

We performed a systematic literature search of multiple online electronic databases regardless of language. Inclusion criteria entailed randomized, placebo controlled trials and IBS defined by accepted symptom-based criteria. Meta-analysis was conducted to evaluate the summary odds ratios (ORs) and 95% confidence intervals (CIs) of combined studies for the primary and secondary outcomes using a random-effects model based on the DerSimonian and Laird method to reflect both within- and between study variability. We assessed heterogeneity using χ(2) test and the inconsistency index statistic (I(2)). Significant heterogeneity was defined as I(2) ≥25%. Meta-regression was performed using generalized linear mixed-effects model and study as random effects to estimate the summary OR adjusting for covariate differences across studies and treatment group. Publication bias was assessed by funnel plot analysis.

RESULTS

Systematic review identified 13,700 citations. Eighteen were deemed to be potentially relevant, of which five articles met eligibility. Meta-analysis found rifaximin to be more efficacious than placebo for global IBS symptom improvement (OR=1.57; 95% CI=1.22, 2.01; therapeutic gain=9.8%; number needed to treat (NNT)=10.2), with mild heterogeneity (P=0.25, I(2)=26%). For the key secondary outcome of bloating, raw data were available for four studies. Rifaximin was significantly more likely to improve bloating than placebo (OR=1.55; 95% CI=1.23-1.96; therapeutic gain=9.9%; NNT=10.1), with no significant heterogeneity (P=0.27, I(2)=23%). We found that studies with older patients and more females demonstrated higher response rates, which was consistent regardless of treatment group. In addition, studies with higher cumulative dose tended to report a higher response rate. Of the covariates evaluated, we found age to be most predictive of response, with a correlation coefficient of 0.97 between aggregate response rate and mean age in the placebo groups. Although studies with higher cumulative dose tended to show increased response rates, this was also seen consistently in both the treated and placebo groups. Adverse effects were similar among patients receiving rifaximin or placebo in all studies. The most common adverse events (AEs) (≤10%) with rifaximin were headache, upper respiratory infection, nausea, nasopharygitis, diarrhea, and abdominal pain. Serious AEs were rare (<1%) and similar with rifaximin and placebo.

CONCLUSIONS

Rifaximin proved more effective than placebo for global symptoms and bloating in IBS patients. The modest therapeutic gain was similar to that yielded by other currently available therapies for IBS. AEs were similar between rifaximin and placebo.

Prucalopride: safety, efficacy and potential applications

Chronic constipation is a very common functional gastrointestinal disorder which can be associated with significant impairments in quality of life for some people with the condition. Its management has, traditionally, been based on dietary and lifestyle changes and the use of a variety of laxative agents. The evidence base for the efficacy of the latter is, in many cases, slim. Not surprisingly, many patients remain dissatisfied with laxatives thus leading to the development of more pharmacological approaches. Among these approaches is the use of prokinetic agents; while prior molecules have been troubled by lack of selectivity and cardiac side effects, the new agent, prucalopride, appears to be highly selective for the serotonin 5-HT4 receptor and is, therefore, a potent stimulator of gut motility. In three large pivotal randomized controlled trials, prucalopride has been effective in relieving the cardinal symptoms of chronic constipation; these effects have been sustained in open-label follow up for as long as 18 months. The safety profile has been encouraging and, especially so, the absence of arrhythmogenic potential. Studies in men, in constipation-predominant irritable bowel syndrome and in other motor disorders are eagerly awaited.

Gut memories: towards a cognitive neurobiology of irritable bowel syndrome

The brain and the gut are engaged in continual crosstalk along a number of pathways collectively termed the 'brain-gut axis'. Over recent years it has become increasingly clear that dysregulation of the axis at a number of levels can result in disorders such as irritable bowel syndrome (IBS). With recent advances in neuroimaging technologies, insights into the neurobiology of IBS are beginning to emerge. However the cognitive neurobiology of IBS has remained relatively unexplored to date. In this review we summarise the available data on cognitive function in IBS. Moreover, we specifically address three key pathophysiological factors, namely; stress, immune activation and chronic pain, together with other factors involved in the manifestation of IBS, and explore how each of these components may impact centrally, what neurobiological mechanisms might be involved, and consider the implications for cognitive functioning in IBS. We conclude that each factor addressed could significantly impinge on central nervous system function, supporting the view that future research efforts must be directed towards a detailed assessment of cognitive function in IBS.

Do interactions between stress and immune responses lead to symptom exacerbations in irritable bowel syndrome?

Irritable bowel syndrome (IBS) is a common, debilitating gastrointestinal (GI) disorder, with a worldwide prevalence of between 10% and 20%. This functional gut disorder is characterized by episodic exacerbations of a cluster of symptoms including abdominal pain, bloating and altered bowel habit, including diarrhea and/or constipation. Risk factors for the development of IBS include a family history of the disorder, childhood trauma and prior gastrointestinal infection. It is generally accepted that brain-gut axis dysfunction is fundamental to the development of IBS; however the underlying pathophysiological mechanisms remain elusive. Additional considerations in comprehending the chronic relapsing pattern that typifies IBS symptoms are the effects of both psychosocial and infection-related stresses. Indeed, co-morbidity with mood disorders such as depression and anxiety is common in IBS. Accumulating evidence points to a role for a maladaptive stress response in the initiation, persistence and severity of IBS-associated symptom flare-ups. Moreover, mechanistically, the stress-induced secretion of corticotropin-releasing factor (CRF) is known to mediate changes in GI function. Activation of the immune system also appears to be important in the generation of IBS symptoms and increasing evidence now implicates low-grade inflammation or immune activation in IBS pathophysiology. There is a growing body of research focused on understanding at a molecular, cellular and in vivo level, the relationship between the dysregulated stress response and immune system alterations (either individually or in combination) in the etiology of IBS and to the occurrence of symptoms.

Relationships among the lactulose breath test, intestinal gas volume, and gastrointestinal symptoms in patients with irritable bowel syndrome

BACKGROUND AND AIMS

Irritable bowel syndrome (IBS) patients frequently complain of gas-related symptoms, and the lactulose breath test (LBT) is a test that assesses the amount of fermented gas generated by bacteria in the bowel. We aimed to assess the relationship among intestinal gas volume, LBT result, and gastrointestinal symptom score in healthy control and functional bowel disorder (FBD) subjects.

METHOD

In 84 IBS subjects, 24 FBD subjects other than IBS, and 25 healthy controls, a symptom questionnaire that enquired about seven main symptoms, plain abdominal radiography and a LBT were checked on the same day. The intestinal gas volume was calculated as the gas volume score (GVS) with a digitalized image of plain supine abdominal radiographs.

RESULTS

The GVS was greater in the LBT (+) group compared to the LBT (-) group (P = 0.02). The GVS was greater in the FBD and IBS groups than in the control group (P < 0.01). The GVS showed low but positive correlations with the severity and frequency of bloating, flatulence, abdominal pain, constipation, and tenesmus (P < 0.05). The severity of flatulence (P = 0.02) and the frequency of bloating (P = 0.02) in the LBT (+) group were significantly higher than those in the LBT (-) group.

CONCLUSIONS

Subjects with positive LBT had more gas-related symptoms and greater gas volume scores. Gas-related symptoms, positive LBT and increased GVS were significantly associated to each other. These findings can broaden the understanding of the pathophysiologic mechanisms of gas-related symptoms in IBS.

Treatment of irritable bowel syndrome: beyond fiber and antispasmodic agents

Irritable bowel syndrome (IBS) is a chronic functional disorder of the gastrointestinal tract of unknown etiology. The diagnosis of IBS is made clinically, using symptom-based criteria such as the Manning or Rome criteria. Medical therapy for this condition has traditionally been directed towards symptom relief, using fiber or antispasmodic agents. In recent years, emerging data have confirmed the efficacy of antidepressants, psychological therapies, 5-HT(3) antagonists, 5-HT(4) agonists, and probiotics in the short-term treatment of IBS, although whether these therapies influence the long-term course of the disease is unknown. Increasing knowledge regarding the pathophysiological mechanisms underlying IBS has resulted in a number of novel molecular treatments, which show promise. These include therapies targeting gastrointestinal mucosal chloride channels and guanylate cyclase-C receptors, as well as highly selective agents influencing serotonergic transmission that, at the time of writing, do not appear to have any severe deleterious effects. In this article we provide a summary of current and emerging therapies in this field.

Pathogenic factors involved in the development of irritable bowel syndrome: focus on a microbial role

Irritable bowel syndrome (IBS) is a symptom complex characterized by recurrent abdominal pain or discomfort, and accompanied by abnormal bowel habits, in the absence of any discernible organic abnormality. Its origin remains unclear, partly because multiple pathophysiologic mechanisms are likely to be involved. A significant proportion of patients develop IBS symptoms after an episode of gastrointestinal infection. In addition to gastrointestinal pathogens, recent evidence suggests that patients with IBS have abnormal composition and higher temporal instability of their intestinal microbiota. Because the intestinal microbiota is an important determinant of normal gut function and immunity, this instability may constitute an additional mechanism that leads to symptom generation and IBS. More importantly, a role for altered microbiota composition in IBS raises the possibility of therapeutic interventions through selective antibiotic or probiotic administration. The new concept of functional bowel diseases incorporates the bidirectional communication between the gut and the central nervous system (gut-brain axis), which may explain the multiple facets of IBS by linking emotional and cognitive centers of the brain with peripheral functioning of the gastrointestinal tract and vice versa.

Constipation, IBs and the 5-HT4 Receptor: What Role for Prucalopride?

After the problems associated with the non-selective 5-HT4 receptor agonists cisapride and tegaserod, the 5-HT4 receptor is now beginning to come in from the cold. Thus, prucalopride is now the first of a new class of drug defined by selectivity and high intrinsic activity at the 5-HT4 receptor. Prucalopride has been developed for treatment of chronic constipation rather than constipation-predominant irritable bowel syndrome (IBS). This follows the trend of first evaluating new gastrointestinal (GI) prokinetic drugs in disorders where disrupted GI motility is known to exist, rather than in a functional bowel disorder where changes in motility are uncertain. If prucalopride is not progressed towards the IBS indication, it has at least shown the way for other selective 5-HT4 receptor agonists. Most notable among these is TD-5108 (velusetrag), also characterized by good selectivity at the 5-HT4 receptor, high intrinsic activity and efficacy in patients with chronic constipation.

Asian consensus on irritable bowel syndrome

BACKGROUND AND AIMS

Many of the ideas on irritable bowel syndrome (IBS) are derived from studies conducted in Western societies. Their relevance to Asian societies has not been critically examined. Our objectives were to bring to attention important data from Asian studies, articulate the experience and views of our Asian experts, and provide a relevant guide on this poorly understood condition for doctors and scientists working in Asia.

METHODS

A multinational group of physicians from Asia with special interest in IBS raised statements on IBS pertaining to symptoms, diagnosis, epidemiology, infection, pathophysiology, motility, management, and diet. A modified Delphi approach was employed to present and grade the quality of evidence, and determine the level of agreement.

RESULTS

We observed that bloating and symptoms associated with meals were prominent complaints among our IBS patients. In the majority of our countries, we did not observe a female predominance. In some Asian populations, the intestinal transit times in healthy and IBS patients appear to be faster than those reported in the West. High consultation rates were observed, particularly in the more affluent countries. There was only weak evidence to support the perception that psychological distress determines health-care seeking. Dietary factors, in particular, chili consumption and the high prevalence of lactose malabsorption, were perceived to be aggravating factors, but the evidence was weak.

CONCLUSIONS

This detailed compilation of studies from different parts of Asia, draws attention to Asian patients' experiences of IBS.

Small intestinal bacterial overgrowth in irritable bowel syndrome: systematic review and meta-analysis

BACKGROUND & AIMS

Small intestinal bacterial overgrowth (SIBO) has been proposed as an etiologic factor in irritable bowel syndrome (IBS), but evidence is conflicting. We conducted a systematic review and meta-analysis of the prevalence of SIBO in IBS.

METHODS

MEDLINE and EMBASE were searched up to November 2008. Case series and case-control studies applying diagnostic tests for SIBO in unselected adults meeting diagnostic criteria for IBS were eligible. Prevalence of a positive test for SIBO was extracted and pooled for all studies, and compared between cases and controls using an odds ratio and 95% confidence interval (CI).

RESULTS

Twelve studies were identified containing 1921 subjects meeting criteria for IBS. Pooled prevalence of a positive lactulose or glucose hydrogen breath test was 54% (95% CI, 32%-76%) and 31% (95% CI, 14%-50%), respectively, with statistically significant heterogeneity between study results. Prevalence of a positive jejunal aspirate and culture was 4% (95% CI, 2%-9%). The pooled odds ratio for any positive test for SIBO in cases compared with healthy asymptomatic controls was 3.45 (95% CI, 0.9-12.7) or 4.7 (95% CI, 1.7-12.95), depending on the criteria used to define a positive test, with statistically significant heterogeneity for both.

CONCLUSIONS

Prevalence of SIBO in individuals meeting diagnostic criteria for IBS was highest with breath testing. The prevalence in cases with IBS compared with controls varied according to criteria used to define a positive test. The role of testing for SIBO in individuals with suspected IBS remains unclear.

Efficacy of 5-HT3 antagonists and 5-HT4 agonists in irritable bowel syndrome: systematic review and meta-analysis

OBJECTIVES

Irritable bowel syndrome (IBS) is a chronic functional disorder. 5-Hydroxytryptamine (5-HT) is a key modulator of gastrointestinal sensorimotor function. Many patients have IBS that can be difficult to treat, which has led to the development of newer agents, such as 5-HT(3) antagonists and 5-HT(4) agonists. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to estimate the efficacy of all available 5-HT agents in IBS.

METHODS

MEDLINE, EMBASE, and the Cochrane Controlled Trials Register were searched (up to June 2008). Trials recruiting adults with IBS in primary, secondary, or tertiary care comparing 5-HT(3) antagonists or 5-HT(4) agonists with placebo were eligible. Dichotomous symptom data were pooled to obtain a relative risk (RR) of remaining symptomatic after therapy, with a 95% confidence interval (CI). The number needed to treat (NNT) was calculated from the reciprocal of the risk difference.

RESULTS

The strategic search identified 1,593 citations. A total of 29 RCTs were eligible for inclusion; placebo was compared with 5-HT(3) antagonists in 11 RCTs, with tegaserod in 11, and with mixed 5-HT(3) antagonists/5-HT(4) agonists in 7. The study quality was generally high. The RR of IBS symptoms persisting with 5-HT(3) antagonists vs. placebo was 0.78 (95% CI: 0.71-0.86), with a similar benefit for both alosetron and cilansetron. Tegaserod was also superior to placebo (RR=0.85; 95% CI: 0.80-0.90). Renzapride and cisapride had no benefit in IBS.

CONCLUSIONS

Alosetron, cilansetron, and tegaserod are all effective in the treatment of IBS. Serious adverse events were rare in the eligible RCTs included in this systematic review.

Irritable bowel syndrome and inflammatory bowel disease: infectious gastroenteritis-related disorders?

Infectious gastroenteritis may be one of the important factors in the development of irritable bowel syndrome (IBS), with affected individuals often categorized as having post-infectious IBS (PI-IBS), and is linked to the onset of symptoms in approximately 10-20% of patients diagnosed with IBS. Intestinal mucosal infiltration of T cells and mast cells, and enterochromaffin cell hyperplasia are significant immunological and pathological findings that reveal the pathogenesis of PI-IBS, and results of laboratory studies using animal models of PI-IBS clearly support clinical evidence. Recently, infectious gastroenteritis has also been suggested to be associated with the development of inflammatory bowel disease (IBD), and various studies have suggested that individuals with IBS or IBS-like symptoms may be susceptible to initiation of IBD. However, it is still unclear whether infectious gastroenteritis is directly or indirectly (through PI-IBS) linked to the initiation of IBD. Additional studies are necessary to understand the clinical overlap among infectious gastroenteritis, IBS, and IBD.

Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis

OBJECTIVE

To determine the effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

Medline, Embase, and the Cochrane controlled trials register up to April 2008. Review methods Randomised controlled trials comparing fibre, antispasmodics, and peppermint oil with placebo or no treatment in adults with irritable bowel syndrome were eligible for inclusion. The minimum duration of therapy considered was one week, and studies had to report either a global assessment of cure or improvement in symptoms, or cure of or improvement in abdominal pain, after treatment. A random effects model was used to pool data on symptoms, and the effect of therapy compared with placebo or no treatment was reported as the relative risk (95% confidence interval) of symptoms persisting.

RESULTS

12 studies compared fibre with placebo or no treatment in 591 patients (relative risk of persistent symptoms 0.87, 95% confidence interval 0.76 to 1.00). This effect was limited to ispaghula (0.78, 0.63 to 0.96). Twenty two trials compared antispasmodics with placebo in 1778 patients (0.68, 0.57 to 0.81). Various antispasmodics were studied, but otilonium (four trials, 435 patients, relative risk of persistent symptoms 0.55, 0.31 to 0.97) and hyoscine (three trials, 426 patients, 0.63, 0.51 to 0.78) showed consistent evidence of efficacy. Four trials compared peppermint oil with placebo in 392 patients (0.43, 0.32 to 0.59).

CONCLUSION

Fibre, antispasmodics, and peppermint oil were all more effective than placebo in the treatment of irritable bowel syndrome.

Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis

OBJECTIVE

To determine the effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

Medline, Embase, and the Cochrane controlled trials register up to April 2008. Review methods Randomised controlled trials comparing fibre, antispasmodics, and peppermint oil with placebo or no treatment in adults with irritable bowel syndrome were eligible for inclusion. The minimum duration of therapy considered was one week, and studies had to report either a global assessment of cure or improvement in symptoms, or cure of or improvement in abdominal pain, after treatment. A random effects model was used to pool data on symptoms, and the effect of therapy compared with placebo or no treatment was reported as the relative risk (95% confidence interval) of symptoms persisting.

RESULTS

12 studies compared fibre with placebo or no treatment in 591 patients (relative risk of persistent symptoms 0.87, 95% confidence interval 0.76 to 1.00). This effect was limited to ispaghula (0.78, 0.63 to 0.96). Twenty two trials compared antispasmodics with placebo in 1778 patients (0.68, 0.57 to 0.81). Various antispasmodics were studied, but otilonium (four trials, 435 patients, relative risk of persistent symptoms 0.55, 0.31 to 0.97) and hyoscine (three trials, 426 patients, 0.63, 0.51 to 0.78) showed consistent evidence of efficacy. Four trials compared peppermint oil with placebo in 392 patients (0.43, 0.32 to 0.59).

CONCLUSION

Fibre, antispasmodics, and peppermint oil were all more effective than placebo in the treatment of irritable bowel syndrome.

Probiotics in irritable bowel syndrome: an immunomodulatory strategy?

The clear delineation of a post-infective variety of IBS, as well as the description, in a number of studies, of evidence of low-grade inflammation and immune activation in IBS, suggest a role for a dysfunctional relationship between the indigenous flora and the host in IBS and, accordingly, provide a clear rationale for the use of probiotics in this disorder. Other modes of action, including bacterial displacement and alterations in luminal contents, are also plausible. While clinical evidence of efficacy is now beginning to emerge, a review of available trials emphasizes the importance of a clear definition of strain selection, dose and viability. The possible roles of co-therapy or sequential therapy with antibiotics, probiotics, prokinetics, or other agents also deserves further study. The role of the enteric flora is evidently an area of great potential in IBS; we are on the threshold of a new era of research and therapy for this common disorder.

Sigmoid-colonic motility in health and irritable bowel syndrome: a role for 5-hydroxytryptamine

Abstract Evidence suggests that sigmoid-colonic motility is increased in patients with irritable bowel syndrome (IBS). 5-Hydroxytryptamine (5-HT) plays a role in the control of motility, but its involvement in the dysmotility seen in IBS remains unclear. To investigate the relationship between platelet depleted plasma 5-HT (PDP 5-HT) concentration and sigmoid-colonic motility in patients with IBS and healthy volunteers. Pre- and postprandial PDP 5-HT concentrations were assessed while recording sigmoid-colonic motility in 35 IBS patients (aged 19-53 years, eight male) and 16 healthy volunteers (aged 18-39 years, six male). Motility was recorded using a five-channel solid-state catheter introduced to a depth of 35 cm into an unprepared bowel. 5-Hydroxytryptamine concentration was measured by reverse-phase HPLC with fluorimetric detection. Irritable bowel syndrome patients had elevated concentrations of PDP 5-HT under fasting (P < 0.004) and fed (P = 0.079) conditions compared with controls. Likewise, they exhibited increased sigmoid-colonic motility under fasting (activity index: P < 0.02) and fed (P < 0.05) conditions compared with controls. Platelet depleted plasma 5-HT concentration positively correlated with colonic activity index under both fasting (r = 0.402; P = 0.003) and fed (r = 0.439; P = 0.001) conditions. These data show a possible relationship between endogenous concentrations of 5-HT and sigmoid-colonic motility recorded in both IBS and healthy subjects.

Effect of tegaserod on colonic transit time in male patients with constipation-predominant irritable bowel syndrome

BACKGROUND AND AIMS

Tegaserod is approved for the treatment of constipation-predominant irritable bowel syndrome (C-IBS) in females. The aim of this study was to evaluate the effect of tegaserod on colonic transit time (CTT) and symptoms in male patients with C-IBS.

METHODS

Forty-four males with C-IBS (Rome II) were enrolled. After a baseline washout period of 2 weeks, 40 patients were randomized to 6 mg twice daily of tegaserod or placebo for 12 weeks. Daily bowel habits and weekly satisfactory relief of symptoms were recorded. Total and segmental CTT were measured using radiopaque markers at baseline and after treatment.

RESULTS

The mean +/- SD for the total colonic, right colonic, left colonic and rectosigmoid transit time (in hours) were 18.96 +/- 3.92, 7.74 +/- 1.55, 5.64 +/- 1.51 and 5.58 +/- 2.2 in the tegaserod group compared to 22.47 +/- 3.73, 9.69 +/- 2.33, 6.6 +/- 1.32 and 6.18 +/- 2.22 in the placebo group at the end of 12 weeks. There was a statistically significant difference in the total, right and left CTT in the tegaserod group (P < 0.05) at the end of treatment. Global satisfactory relief at the end of 12 weeks was 75% in the tegaserod group and 50% in the placebo group (P > 0.05). Greater stool frequency occurred in the tegaserod group (P > 0.05). There was a significant decrease in the stool consistency at the end of 12 weeks in patients treated with tegaserod (P < 0.05).

CONCLUSIONS

Tegaserod causes significant acceleration of CTT in male patients with C-IBS. Although there was a trend towards improvement in bowel symptoms in the treated group, this effect was not statistically significant.

Risk factors for irritable bowel syndrome in Turkish population: role of food allergy

GOALS

The aim of this study was to determine the prevalence of food hypersensitivity in Turkish patients with irritable bowel syndrome (IBS).

BACKGROUND

The IBS is a chronic disease of the gastrointestinal tract characterized by abdominal pain, distension, meteorism and either diarrhea or constipation. The role of diet in the pathogenesis of IBS remains controversial. Many investigators have shown that individual foods can trigger symptoms in some patients; nevertheless, the percentage of patients that benefit from dietary manipulation ranges from 15% to 67% in different reports.

STUDY

Skin prick test to 11 common allergens, total IgE, eosinophilic cationic protein and eosinophil counts were evaluated in 100 patients satisfying the Rome II criteria and compared with 25 healthy controls. The history and physical examination of the groups were recorded and Beck Depression and Anxiety Inventories were performed.

RESULTS

One hundred patients were entered into the study with a mean age of 45.63+/-12.91 years. Of the patients 53 had constipation predominant, 19 had diarrhea predominant, and 28 had alternating type IBS. Skin prick tests positivity were more common among the IBS patients in comparison with controls (25% and 1%, respectively, P<0.05). Mean IgE values were higher in patients than controls (70.83+/-66.05 and 15.20+/-14.01 IU/mL, respectively, P<0.000). Eosinophilic cationic protein values were also higher in IBS patients than controls (16.75+/-11.28 and 11.56+/-4.72, respectively, P<0.05) Evaluation of Beck Depression Inventory showed that tendency to depression in patients with IBS was 38% and 4% in controls (P<0.05).

CONCLUSIONS

According to our results, in patients complaining of IBS it is of importance to search for a food component. Clinical improvements can be observed after the introduction of an adequate exclusion diet.

Relationship of abdominal bloating to distention in irritable bowel syndrome and effect of bowel habit

BACKGROUND & AIMS

The relationship between the sensation of bloating, often ranked as the most bothersome symptom by patients with irritable bowel syndrome (IBS), and actual distention manifest as an increase in abdominal girth is controversial. Investigation of this problem has been hampered by the lack of a reliable ambulatory technique to measure abdominal girth. The aim of this study was to use the technique of abdominal inductance plethysmography to compare diurnal variation in girth in IBS patients and healthy volunteers, relating these changes to the sensation of bloating.

METHODS

Abdominal girth was recorded for 24 hours in 20 IBS-constipation (age, 18-73 y), 20 IBS-diarrhea (age, 25-62 y) and 10 IBS-alternating (age, 21-59 y) female patients meeting Rome II criteria and 20 healthy female controls (age, 18-67 y). All subjects pursued normal daily activities, recording their symptoms of bloating and pain together with bowel habit.

RESULTS

All patients with IBS, irrespective of bowel habit, reported significantly greater bloating than controls (P < .0001). Forty-eight percent of patients also showed distention beyond the 90% control range, with this being most prominent in IBS-constipation. Bloating correlated strongly only with distention in IBS-constipation (r > or = 0.48; P < or = .02). Neither bloating nor distention in IBS was related to body mass index, age, parity, or psychologic status.

CONCLUSIONS

Abdominal distention is a clearly definable phenomenon in IBS that can reach 12 cm. However, it only occurs in half of patients reporting bloating, and the 2 only correlate in IBS-constipation. Bloating and distention may differ pathophysiologically and this appears to be reflected in the bowel habit subtype.

Bacteria and irritable bowel syndrome: the evidence for small intestinal bacterial overgrowth

Irritable bowel syndrome (IBS) is a complex, yet common diagnosis in gastroenterology. Recent data suggest the increasing importance of bacteria in the pathophysiology of IBS. Some studies have shown that IBS can be precipitated by an acute case of gastroenteritis. These pathogenic organisms may contribute to long-term gut dysfunction. In another line of effort, a growing body of evidence links IBS to the presence of excessive bacteria in the small bowel, called bacterial overgrowth. Although the means by which this is determined have been indirect, studies demonstrating the benefit of unabsorbed antibiotics suggest that reduction in gut flora is important. Further work has also examined bacterial overgrowth in the context of the various symptoms of patients with IBS. These symptom complexes include constipation, diarrhea, and alternating forms of the condition. Although this idea seems initially counterintuitive, it has been demonstrated that the fermentation of methane in the gut is associated with and can result in the slowing of intestinal transit, resulting in constipation. In this review, these topics are discussed and outlined.

A course of instruction for women with irritable bowel syndrome

OBJECTIVE

The aim of this study was to determine the effects a course of instruction about irritable bowel syndrome (IBS) might have on symptoms, psychological well-being, and medical care requirements in these patients.

METHODS

Twenty-nine women with IBS participated in a programme of instruction on medical care, physical activity, stress-management, diet and health insurance. The women completed the Gastrointestinal Symptom Rating Scale and the Psychological General Well-Being Index and provided information about their requirements of medical care before and after the course.

RESULTS

Twenty-three of the women included, completed the questionnaires at 12 months after the course. When comparing these values to those at baseline, there were improvements in abdominal pain (p < 0.037) and vitality (p < 0.045) as well as a reduction in the number of visits to physicians (p < 0.037) and dieticians (p < 0.042).

CONCLUSION

Information related to the disease, might help women with IBS to perceive less pain and more vitality and thereby experience a higher quality of life.

PRACTICE IMPLICATIONS

A course of instruction for patients with IBS may be of benefit for the patients, and could be a part of a multicomponent approach in the treatment of this patient group.

Functional findings in irritable bowel syndrome

The pathophysiology of IBS is complex and still incompletely known. Both central and peripheral factors, including psychosocial factors, abnormal GI motility and secretion, and visceral hypersensitivity, are thought to contribute to the symptoms of IBS. Several studies have demonstrated altered GI motor function in IBS patients and the pattern differs between IBS subgroups based on the predominant bowel pattern. Few studies have so far addressed GI secretion in IBS, but there are some evidence supporting altered secretion in the small intestine of IBS patients. Visceral hypersensitivity is currently considered to be perhaps the most important pathophysiological factor in IBS. Importantly, several external and internal factors can modulate visceral sensitivity, as well as GI motility, and enhanced responsiveness within the GI tract to for instance stress and nutrients has been demonstrated in IBS patients. Today IBS is viewed upon as a disorder of dysregulation of the so-called brain-gut axis, involving abnormal function in the enteric, autonomic and/or central nervous systems, with peripheral alterations probably dominating in some patients and disturbed central processing of signals from the periphery in others.

Hypnosis for irritable bowel syndrome: the quest for the mechanism of action

Irritable bowel syndrome (IBS) is a very common condition in the Western part of the world, and it accounts for a large proportion of the workload of a gastroenterologist. Unfortunately, the pathogenesis and pathophysiology of the syndrome are incompletely understood, and the treatment options are limited. However, hypnotherapy is one treatment option that has proven to be very useful in IBS. The mechanisms of action explaining why hypnosis is effective for IBS are not altogether known, but recent studies have shed some light on this issue. These studies, and what can be learned from them about how hypnosis impacts IBS, are reviewed in this article. Hypnosis may affect IBS partly through changes in colorectal sensitivity and improvement in psychological factors. The effects on GI motility and the autonomic nervous system are less clear and need further evaluation.

Altered 5-hydroxytryptamine signaling in patients with constipation- and diarrhea-predominant irritable bowel syndrome

BACKGROUND & AIMS

Evidence suggests that postprandial platelet-depleted plasma 5-hydroxytryptamine (5-HT) concentrations may be abnormal in irritable bowel syndrome (IBS). However, interpretation of the data has been hampered by the variable methodology and rather small numbers used in previous studies. Therefore, the aim of this study was to measure concentrations of platelet-depleted plasma 5-HT and its metabolite 5-HIAA under fasting and fed conditions in a large group of patients with diarrhea-predominant (d-) and constipation-predominant (c-) IBS, compared with controls. The ratio of plasma 5-HIAA:5-HT and platelet stores was also assessed.

METHODS

Twenty-nine c-IBS patients (aged, 19-53 years), 55 d-IBS patients (aged, 19-52 years), and 35 healthy volunteers (aged, 18-46 years) had platelet-depleted plasma 5-HT/5-HIAA concentrations measured using reverse-phase, high-performance liquid chromatography with fluorimetric detection before and after a standard meal.

RESULTS

d-IBS patients had raised platelet-depleted plasma 5-HT concentrations under fasting and fed conditions (P < .05). However, the postprandial relative to fasting concentration was similar to controls. In contrast, c-IBS patients failed to show an increase in platelet-depleted plasma 5-HT concentration with meal ingestion compared with controls (P < .01). c-IBS was associated with decreased 5-HIAA (P < .01) but normal 5-HIAA:5-HT ratio and d-IBS with normal 5-HIAA concentrations but reduced 5-HIAA:5-HT ratio (P < .005). C-IBS but not d-IBS patients had increased platelet 5-HT.

CONCLUSIONS

These results support the concept that d-IBS is characterized by reduced 5-HT reuptake, whereas impaired release may be a feature of c-IBS. These results also provide a rational basis for current pharmacologic approaches involving modulation of different 5-HT receptors in c- and d-IBS.

Nutrition and motility disorders

The purpose of this article is to give an overview of the relation between feeding and gastrointestinal symptoms and complaints, and to review different motility disorders that have implications for food intake. We also report the consequences for nutrition state and the evidence-based principles of dietary modification in patients with motility disorders.

Irritable bowel syndrome and inflammatory bowel disease: interrelated diseases?

In the past inflammatory bowel disease (IBD), celiac disease and irritable bowel syndrome (IBS) were regarded as completely separate disorders. Now, with the description of inflammation, albeit low-grade, in IBS, and of symptom overlap between IBS and celiac disease, this contention has come under question. Is there true overlap between these disorders? Despite the limitations of available data one cannot but be struck by some areas of apparent convergence: IBD and celiac disease in remission, lymphocytic colitis and microscopic inflammation in IBS, in general, and, especially, in the post-infectious IBS category. The convergence between latent celiac disease and sub-clinical IBD, on the one hand, and IBS, on the other, appears, based on available evidence, to be somewhat spurious and may largely relate to misdiagnosis, a phenomenon which may also explain the apparent evolution of IBS into IBD in some studies. Similarities between IBS and lymphocytic colitis are more striking and less readily dismissed; as for IBS, well documented instances of progression of lymphocytic colitis to full-blown IBD are infrequent, suggesting a true separation between this disorder and classical IBD. Do IBS and lymphocytic colitis represent different responses to similar triggers? Will some of the 'inflamed' IBS subgroup be reclassified as part of the spectrum of lymphocytic colitis in the future? Will inflammation emerge as a common underlying factor in the pathogenesis of IBS? The answer to these and many questions must await further study of this fascinating area.

Disturbances of motility and visceral hypersensitivity in irritable bowel syndrome: biological markers or epiphenomenon

Motility and visceral hypersentitivity are regarded as the primary mechanisms of symptom development in irritable bowel syndrome(IBS). While a variety of motor abnormalities have been described throughout the gastrointestinal tract in IBS, their specificity and relationship to symptoms remain unclear. Visceral hypersensitivity is ubiquitous in functional gastrointestinal disease and is especially common in IBS. Again, however, its specificity for IBS has been questioned. Many factors, including stress and psychopathology,complicate the interpretation of these phenomena and new re-search suggests that mucosal inflammation and luminal factors may be more fundamental to the etiology of this common disorder.

Current concepts of the irritable bowel syndrome

The irritable bowel syndrome is one of the most common clinical problems encountered by the generalist and gastroenterologist. The goal of this review is to critically evaluate, based on available peer-reviewed literature, the current status of our understanding of the pathophysiology of the irritable bowel syndrome. The epidemiology of this disorder, including the characteristics of its presentation, natural history and associated phenomena, have been clarified. Differences between those who seek specialist care ('the consulters') and those in the community are now recognized. While, in both, symptoms may be similar in nature and severity; 'the consulters' are differentiated by how they react to their complaints. In terms of pathophysiology, the focus has moved to visceral sensation and central perception and has led to the identification of visceral hypersensitivity, visceral hyperalgesia and abnormal central perception of visceral events. This is not to dismiss dysmotility; subtle abnormalities in gas transit may be closely associated with the induction of certain symptoms. On the psychological front, attention now focuses on such complex issues as somatosization, abuse and response to major life events. Interactions between enteric flora, mucosal inflammation, immune phenomena and the enteric neuro-muscular apparatus also attract interest; the entity of post-infectious irritable bowel is now clearly recognized and there is experimental evidence to suggest a role for inflammation. While the precise aetiology of irritable bowel syndrome remains uncertain, considerable progress has been made, with recent advances in pathophysiology offering hope for the development of new therapeutic approaches.

Gut-focused hypnotherapy normalizes disordered rectal sensitivity in patients with irritable bowel syndrome

BACKGROUND

We have previously shown that hypnotherapy alters rectal sensitivity in some patients with irritable bowel syndrome. However, this previous study used incremental volume distension of a latex balloon, which might be susceptible to subject response bias and might compromise the assessment of compliance. In addition, the study group was symptomatically rather than physiologically defined.

AIM

To assess the effect of hypnotherapy on rectal sensitivity in hypersensitive, hyposensitive and normally sensitive irritable bowel syndrome patients using a distension technique (barostat) that addresses these technical issues.

METHODS

Twenty-three irritable bowel syndrome (Rome I) patients (aged 24-72 years) were assessed before and after 12 weeks of hypnotherapy in terms of rectal sensitivity, symptomatology, anxiety and depression. Normal values for sensitivity were established in 17 healthy volunteers (aged 20-55 years).

RESULTS

Compared with controls, 10 patients were hypersensitive, seven hyposensitive and six normally sensitive before treatment. Following hypnotherapy, the mean pain sensory threshold increased in the hypersensitive group (P = 0.04) and decreased in the hyposensitive group, although the latter failed to reach statistical significance (P = 0.19). Normal sensory perception was unchanged. Sensory improvement in the hypersensitive patients tended to correlate with a reduction in abdominal pain (r = 0.714, P = 0.07).

CONCLUSION

Hypnotherapy improves abnormal sensory perception in irritable bowel syndrome, leaving normal sensation unchanged.

Psychological and physiological responses to postprandial mental stress in women with the irritable bowel syndrome

OBJECTIVE

To investigate the psychological (affective and symptomatic) and physiological (autonomic and cortisol) responses to postprandial mental stress in women with irritable bowel syndrome (IBS). It was hypothesized that patients with IBS would show exaggerated autonomic and cortisol responses to the psychological stressor and that the stressor would enhance gastrointestinal symptoms.

METHOD

Twenty-four women with IBS and 20 healthy women participated in the two-day study protocol. Both days were identical, with the exception that on one day, a stressful mental task was completed after ingestion of a standard meal. Heart rate variability, cortisol, affective, and symptomatic responses were measured before and after application of the stressor.

RESULTS

Patients with IBS demonstrated increased negative affect at baseline and in response to the stressor. Gastrointestinal symptoms were not affected by the stressor. Appraisal of the stressor by patients with IBS was not different from that of controls. There were no group differences in the autonomic response to the stressor. There was no overall cortisol response to the stressor in either group.

CONCLUSIONS

Patients with IBS respond with greater negative affect to postprandial psychological stress as well as to food intake alone, and they can be distinguished from controls on the basis of self-report data. Patients with IBS cannot be differentiated from controls on the basis of the pattern of changes in sympathetic activation after the mental stressor. The stressor used in this study did not elicit a cortisol response in either group.

Common functional gastrointestinal disorders: nonulcer dyspepsia and irritable bowel syndrome

Up to 35% of the world population suffer from functional gastrointestinal disorders (FGD), accounting for about 40% of gastroenterologic and 12% of primary care practice. Society incurs high costs from FGD morbidity in terms of medical workups and absenteeism from work. FGD are characterized by chronic and recurrent symptoms of the gastrointestinal (GI) tract without detectable structural or biochemical abnormalities. In the absence of universal biologic markers, the diagnosis is based on consensus symptom criteria (1). This chapter reviews current knowledge of the pathophysiology and provides a practical approach to patients with functional dyspepsia and irritable bowel syndrome, 2 of the most common functional GI syndromes.