Irritable bowel syndrome: relationship of disorders in the transit of a single solid meal to symptom patterns

Critical appraisal of the SIBO hypothesis and breath testing: A clinical practice update endorsed by the European society of neurogastroenterology and motility (ESNM) and the American neurogastroenterology and motility society (ANMS)

BACKGROUND

There is compelling evidence that microbe-host interactions in the intestinal tract underlie many human disorders, including disorders of gut-brain interactions (previously termed functional bowel disorders), such as irritable bowel syndrome (IBS). Small intestinal bacterial overgrowth (SIBO) has been recognized for over a century in patients with predisposing conditions causing intestinal stasis, such as surgical alteration of the small bowel or chronic diseases, including scleroderma and is associated with diarrhea and signs of malabsorption. Over 20 years ago, it was hypothesized that increased numbers of small intestine bacteria might also account for symptoms in the absence of malabsorption in IBS and related disorders. This SIBO-IBS hypothesis stimulated significant research and helped focus the profession's attention on the importance of microbe-host interactions as a potential pathophysiological mechanism in IBS.

PURPOSE

However, after two decades, this hypothesis remains unproven. Moreover, it has led to serious unintended consequences, namely the widespread use of unreliable and unvalidated breath tests as a diagnostic test for SIBO and a resultant injudicious use of antibiotics. In this review, we examine why the SIBO hypothesis remains unproven and, given the unintended consequences, discuss why it is time to reject this hypothesis and its reliance on breath testing. We also examine recent IBS studies of bacterial communities in the GI tract, their composition and functions, and their interactions with the host. While these studies provide important insights to guide future research, they highlight the need for further mechanistic studies of microbe-host interactions in IBS patients before we can understand their possible role in diagnosis and treatment of patient with IBS and related disorders.

The Possible Synergistic Pharmacological Effect of an Oral Berberine (BBR) and Curcumin (CUR) Complementary Therapy Alleviates Symptoms of Irritable Bowel Syndrome (IBS): Results from a Real-Life, Routine Clinical Practice Settings-Based Study

Irritable bowel syndrome (IBS) is a prevalent chronic functional gastrointestinal disorder, characterised by recurrent abdominal discomfort and altered bowel movements. IBS cause a significantly negative impact on quality of life (QoL). Growing pharmacological evidence suggests that berberine (BBR) and curcumin (CUR) may mitigate IBS symptoms through multiple complementary synergistic mechanisms, resulting in the attenuation of intestinal inflammation and regulation of bowel motility and gut functions. In the present observational study conducted under real-life routine clinical practice settings, 146 patients diagnosed with IBS were enrolled by general practitioner clinics and pharmacies in Belgium. For the first time, this study assessed the potential synergistic pharmacological effect of a combined oral BBR/CUR supplement (Enterofytol® PLUS, containing 200 mg BBR and 49 mg CUR) (two tablets daily for 2 months), serving as complementary therapy in the management of IBS. Following the 2-month supplementation, significant improvements were observed in the patients' IBS severity index (IBSSI) (47.5%) and all the primary IBS symptoms, such as abdominal discomfort (47.2%), distension (48.0%), intestinal transit (46.8%), and QoL (48.1%) (all p < 0.0001). The improvement in the patients' IBSSI was independent of age, sex, and IBS sub-types. The patients' weekly maximum stool passage frequency decreased significantly (p < 0.0001), and the stool status normalized (p < 0.0001). The patients' need for concomitant conventional IBS treatment decreased notably: antispasmodics by 64.0% and antidiarrhoeals by 64.6%. Minor adverse effects were reported by a small proportion (7.1%) of patients, mostly gastrointestinal. The majority (93.1%) experienced symptom improvement or resolution, with a high satisfaction rate (82.6%) and willingness to continue the supplementation (79.0%). These findings support the potential synergistic pharmacological role of BBR and CUR in IBS, and their co-supplementation may alleviate IBS symptoms and improve QoL.

Clinical Characteristics of Patients Presenting With Bloating as a Predominant Symptom

BACKGROUND

The estimated prevalence of bloating is 15 to 30% in the adult US population and is even higher in patients with disorders of gut-brain interaction (DGBIs). Despite this frequency, there is little research into patients who endorse bloating as a predominant symptom. The aim of this study was to better characterize these patients.

MATERIALS AND METHODS

New patients with DGBIs were asked to identify their 3 most predominant symptoms over the preceding 3 months; those who reported bloating were classified as "bloating predominant." Rome IV and symptom-specific questionnaires were administered to assess for the frequency of DGBIs and other predominant symptoms in this patient population. Using univariable and multivariable modeling, we analyzed the associations between bloating predominance, DGBI subtype, and clinical characteristics.

RESULTS

Of the 586 patients surveyed, 242 (41%) reported predominant bloating. Bloating-predominant patients were more likely to be female, younger, and meet the criteria for IBS-mixed (IBS-M), functional constipation, and functional dyspepsia compared with nonbloating-predominant patients. Bloating-predominant patients were also more likely to endorse concurrently predominant constipation, incomplete evacuation, abdominal pain, belching, and/or nausea. On multivariable logistic regression, constipation and abdominal pain severity were positively associated, although depression was negatively associated with predominant bloating.

CONCLUSIONS

Patients with predominant bloating are more likely to have constipation-related symptoms than diarrhea-related symptoms. They are also more likely to have more severe abdominal pain than patients without predominant bloating. These findings help characterize patients with bloating as a predominant symptom and suggest that diagnosing and treating constipation should be considered as first-line treatment.

Association of serotonin transporter promoter polymorphism (5-HTTLPR) with orocecal transit time in irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a multifactorial disorder with altered intestinal motility, secretion, and sensation. Serotonin (5-HT) stimulates gut motility and alters serotonin signaling that may lead to both intestinal and extraintestinal symptoms in IBS.

AIM

The aim of this study was to examine the association of serotonin transporter gene promoter polymorphism (5-HTTLPR) in IBS with orocecal transit time (OCTT) measured by lactulose hydrogen breath test.

METHOD

This prospective case-control study included 151 IBS patients (mean±SD 37.4±11.6 years, median 36, range 19-68). Ninety-two patients were diarrhea-predominant IBS (D-IBS), 44 constipation-predominant IBS (C-IBS), 15 alternating diarrhea and constipation IBS (M-IBS), and 100 healthy controls (mean±SD 37.2±11.4 years, median 36, range 20-64 years). 5-HTTLPR gene polymorphism was studied by polymerase chain reaction-based method. 5-HT levels were measured by enzyme-linked immunosorbent assay (ELISA). Orocecal transit time (OCTT) was measured by a non-invasive lactulose hydrogen breath test. OCTT was also compared with respect to 5-HTTLPR genotypes in different IBS phenotypes.

RESULTS

Serum serotonin levels were significantly higher in overall IBS patients (152±77 ng/mL, p<0.001), D-IBS (184±76 ng/mL, p<0.001), compared to healthy controls (129±56 ng/mL). There was no difference in 5-HT levels between C-IBS (124±53 ng/mL) and controls. In the case of M-IBS, 5-HT levels were (88±49 ng/mL p<0.05) significantly lower than that of controls. OCTT was significantly shorter in D-IBS patients (95±36 min) as compared to controls (112±41 min). In contrast, C-IBS showed significantly prolonged OCTT (136±54 min). There was a significant difference in OCTT between D-IBS and C-IBS patients (p<0.001). There was no significant association found between OCTT and 5-HTTLPR.

CONCLUSIONS

Serum serotonin concentrations were increased in D-IBS compared to controls and C-IBS. OCTT was shorter in D-IBS and delayed in C-IBS patients. There was no association of 5-HTLPR polymorphism with OCTT.

Probiotics, Prebiotics, and Synbiotics in the Irritable Bowel Syndrome Treatment: A Review

Irritable bowel syndrome is not a life-threatening disease, yet it significantly affects the quality of life and contributes to economic loss. It is estimated that even up to 45% of the world's population can suffer from the disease. The first attempts to diagnose irritable bowel syndrome were made at the end of the 19th century; however, establishing appropriate diagnostic criteria and treatment methods is still ongoing. To date, little is known about the etiology of irritable bowel syndrome; however, growing attention is drawn to the intestinal microbiota as a factor in the disease development. For this reason, researchers have conducted many studies on therapies that modulate the microbiota, among which probiotics, prebiotics, and synbiotics are widely studied. To date, most studies have examined probiotics; however, there are also several studies demonstrating the efficacy of prebiotics and synbiotics. The aim of this review was to summarize findings on the usefulness of probiotics, prebiotics, and synbiotics in the treatment of irritable bowel syndrome.

Irritable Bowel Syndrome in Pregnancy

Irritable bowel syndrome (IBS) affects a significant percentage of the general population and is more common in women. A large proportion of women affected with IBS are of childbearing age; however, there is a paucity of studies and guidelines to specifically address the epidemiology, course, maternal/fetal prognosis, or management of IBS in pregnancy. This scarcity of literature on IBS and pregnancy poses significant challenges to healthcare providers in counseling and managing patients. In this comprehensive review, we summarize the current literature and knowledge gaps regarding the effects of pregnancy on IBS and vice versa, along with the efficacy and safety profiles of commonly used IBS diets and medications in pregnancy. The management of pregnant women with IBS should be multidisciplinary, with emphasis on education and judicious use of dietary modifications and pharmacologic options that are deemed relatively safe during pregnancy.

Ambulatory assessment of colonic motility using the electromagnetic capsule tracking system

BACKGROUND

The Motilis 3D-Transit system tracks electromagnetic capsules as they traverse the gastrointestinal tract. The method is minimally invasive and ambulatory. Analysis has previously been limited to regional gut transit times, but new methods may allow detailed analysis of colonic motility.

METHODS

Parameters of colonic motility were analyzed from 34 3D-Transit recordings performed in healthy volunteers (median age 28 years; 8 F). Characteristic propulsive velocities and lengths of movement were determined to quantify common movement patterns. Data from seven patients with severe chronic diarrhea were included for comparison.

KEY RESULTS

Lack of capsule motion accounted for 82% (75%-87%) of total colonic transit time. Propulsive velocities were distributed with peaks at 0.5 cm/min (antegrade or retrograde) and 50 cm/min (antegrade). Based on velocity and length of propagation, five motor patterns were identified; (a) long fast antegrade, (b) fast antegrade, (c) slow antegrade, (d) slow retrograde, and (e) fast retrograde movements. Long fast antegrade movements were median 21 cm (10-96 cm). Capsule progression was faster during daytime than at night (5.9 cm/h vs 0.8 cm/h; P < 0.01). Colonic transit was faster in patients with chronic diarrhea than in healthy volunteers (5.4 h vs 18.2 h; P = 0.04), with higher capsule velocity (20.4 cm/h vs 4.4 cm/h; P < 0.01).

CONCLUSIONS AND INFERENCES

The 3D-Transit system now allows detailed description of colonic motility and our results are supported by those previously suggested by manometry. It holds promise for future assessment of movement patterns to characterize different diseases and effects of treatment.

Altered white matter microstructure identified with tract-based spatial statistics in irritable bowel syndrome: a diffusion tensor imaging study

The neural mechanisms underlying the pathophysiology of irritable bowel syndrome(IBS) are far from being completely understood. The purpose of the present study was to investigate potential white matter (WM) microstructural changes and underlying causes for WM impairment in IBS using diffusion tensor imaging. The present prospective study involved 19 patients with IBS and 20 healthy controls. Whole-brain voxel-wise analyses of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were performed by tract-based spatial statistics (TBSS) to localize abnormal WM regions between the 2 groups. We found that IBS patients had significantly reduced FA (P < 0.05) in the splenium of the corpus callosum, the right retrolenticular area of the internal capsule and the right superior corona radiata. We also found increased MD (P < 0.05) in the splenium and body of the corpus callosum, the right retrolenticular area of the internal capsule, the right superior corona radiata and the right posterior limb of the internal capsule. In addition, IBS patients had significantly increased AD (P < 0.05) in the splenium of the corpus callosum, the bilateral retrolenticular area of the internal capsule and the left posterior limb of the internal capsule. We conclude that the WM microstructure is changed in IBS and the underlying pathological basis may be attributed to the axonal injury and loss. These results may lead to a better understanding of the pathophysiology of IBS.

All disease begins in the gut: Influence of gastrointestinal disorders and surgery on oral drug performance

The term "disease" conjures a plethora of graphic imagery for many, and the use of drugs to combat symptoms and treat underlying pathology is at the core of modern medicine. However, the effects of the various gastrointestinal diseases, infections, co-morbidities and the impact of gastrointestinal surgery on the pharmacokinetic and pharmacodynamic behaviour of drugs have been largely overlooked. The better elucidation of disease pathology and the role of underlying cellular and molecular mechanisms have increased our knowledge as far as diagnoses and prognoses are concerned. In addition, the recent advances in our understanding of the intestinal microbiome have linked the composition and function of gut microbiota to disease predisposition and development. This knowledge, however, applies less so in the context of drug absorption and distribution for orally administered dosage forms. Here, we revisit and re-evaluate the influence of a portfolio of gastrointestinal diseases and surgical effects on the functionality of the gastrointestinal tract, their implications for drug delivery and attempt to uncover significant links for clinical practice.

Impact of gastrointestinal disease states on oral drug absorption – implications for formulation design – a PEARRL review

Objectives

Drug product performance in patients with gastrointestinal (GI) diseases can be altered compared to healthy subjects due to pathophysiological changes. In this review, relevant differences in patients with inflammatory bowel diseases, coeliac disease, irritable bowel syndrome and short bowel syndrome are discussed and possible in vitro and in silico tools to predict drug product performance in this patient population are assessed.

Key findings

Drug product performance was altered in patients with GI diseases compared to healthy subjects, as assessed in a limited number of studies for some drugs. Underlying causes can be observed pathophysiological alterations such as the differences in GI transit time, the composition of the GI fluids and GI permeability. Additionally, alterations in the abundance of metabolising enzymes and transporter systems were observed. The effect of the GI diseases on each parameter is not always evident as it may depend on the location and the state of the disease. The impact of the pathophysiological change on drug bioavailability depends on the physicochemical characteristics of the drug, the pharmaceutical formulation and drug metabolism. In vitro and in silico methods to predict drug product performance in patients with GI diseases are currently limited but could be a useful tool to improve drug therapy.

Summary

Development of suitable in vitro dissolution and in silico models for patients with GI diseases can improve their drug therapy. The likeliness of the models to provide accurate predictions depends on the knowledge of pathophysiological alterations, and thus, further assessment of physiological differences is essential.

General practitioners' perceptions of irritable bowel syndrome: a Q-methodological study

BACKGROUND

Irritable bowel syndrome (IBS) is a common disorder that imposes a significant burden upon societies, health care and quality of life, worldwide. While a diverse range of patient viewpoints on IBS have been explored, the opinions of the GPs they ideally need to develop therapeutic partnerships with are less well defined.

OBJECTIVE

To explore how GPs perceive IBS, using Q-methodology, which allows quantitative interpretation of qualitative data.

DESIGN AND SETTING

A Q-methodological study of GPs in Leeds, UK.

METHOD

Thirty-three GPs completed an online Q-sort in which they ranked their level of agreement with 66 statements. Factor analysis of the Q-sorts was performed to determine the accounts that predominated in understandings of IBS. Ten of the GPs were interviewed in person and responses to the statements recorded to help explain the accounts.

RESULTS

Analysis yielded one predominant account shared by all GPs-that IBS was a largely psychological disorder. This account overshadowed a debate represented by a minority, polarized between those who viewed IBS as almost exclusively psychological, versus those who believed IBS had an organic basis, with a psychological component. The overwhelming similarity in responses indicates that all GPs shared a common perspective on IBS. Interviews suggested degrees of uncertainty and discomfort around the aetiology of IBS.

CONCLUSION

There was overwhelming agreement in the way GPs perceived IBS. This contrasts with the range of patient accounts of IBS and may explain why both GPs and their patients face difficult negotiations in achieving therapeutic relationships.

The role of Blastocystis sp. and Dientamoeba fragilis in irritable bowel syndrome: a systematic review and meta-analysis

Irritable bowel syndrome (IBS) is globally one of the most prevalent gastrointestinal disorders with a negative impact on quality of life and socio-economic status of patients. Recently, controversial evidences suggest that Blastocystis sp. and Dientamoeba fragilis infections may be implicated in the development of IBS. We performed a systematic review and meta-analysis to examine the possible association regarding this issue. PubMed, ScienceDirect, Scopus, Web of Science, and Cochrane electronic databases were searched (up to February 2017) to identify the relevant studies. Pooled odds ratio (OR) and 95% confidence intervals were estimated using a random effects meta-analysis model on data from included studies. A total of 17 studies including 5882 participants (2527 patients and 3310 controls) met the eligibility criteria. Individuals with Blastocystis infection were found to have a positive association with IBS (OR, 2.19; 95% CI, 1.54-3.13), while this association was not observed for D. fragilis infection (OR, 1.13; 95% CI, 0.22-5.72). In subgroup analysis for Blastocystis infection, the pooled ORs were OR 2.29, 95% CI 1.55-3.41; OR 1.70, 95% CI 0.83-3.44; and OR 3.83, 95% CI 2.34-6.27 for hospital-based, healthy volunteers, and combined controls, respectively. Considering the subtypes, meta-analysis result demonstrated significant positive ORs for ST1 (OR, 4.40; 95% CI, 2.81-6.90) and ST3 (OR, 1.94; 95% CI, 1.36-2.77) to be potential risk factors for IBS. Our results support the existence of a positive association between Blastocystis sp. and IBS. Further studies with more sample size should be performed to better investigate the real impact of these parasites on the occurrence of IBS.

Small intestinal bacterial overgrowth as a cause for irritable bowel syndrome: guilty or not guilty?

PURPOSE OF REVIEW

Small intestinal bacterial overgrowth (SIBO) has been proposed as a cause of irritable bowel syndrome (IBS). However, this relationship has been subject to controversy. This review aims to provide a current perspective on the SIBO-IBS hypothesis.

RECENT FINDINGS

Case-control studies evaluating the prevalence of SIBO in IBS and healthy individuals have shown conflicting results. Moreover, the tests available in routine clinical practice to diagnose SIBO are not valid and lack both sensitivity and specificity. Hence, interpreting the effect of interventions based on these tests is fraught with uncertainty. Furthermore, the SIBO-IBS hypothesis has paved the way to assess antibiotic therapy in nonconstipated IBS, with rifaximin, a nonabsorbable antibiotic, showing modest but significant clinical benefit. However, individuals were not tested for SIBO and the mechanism of action of rifaximin in IBS remains to be elucidated. Preliminary data suggest that rifaximin decreases microbial richness and previous studies have noted antibacterial interventions in IBS to reduce colonic fermentation and improve symptoms. The advent of rapid culture-independent molecular techniques is a promising tool that will seek to clarify and advance our understanding of the gut microbial function.

SUMMARY

The SIBO-IBS hypothesis lacks convincing evidence but remains under scrutiny. The mechanism resulting in symptom improvement after rifaximin treatment in some IBS individuals requires exploration. Novel molecular techniques provide an exciting and challenging opportunity to explore the host-gut microbiota interaction.

An Initial Attack of Urinary Stone Disease Is Associated with an Increased Risk of Developing New-Onset Irritable Bowel Syndrome: Nationwide Population-Based Study

BACKGROUND

The neurotransmitter pathways in irritable bowel syndrome (IBS) and urinary stone attacks are both related to serotonin, and each disease may be influenced by viscero-visceral hyperalgesia. However, the relationship between urinary tract stone disease and IBS has never been addressed. We aimed to investigate the risk of suffering new-onset IBS after an initial urinary stone attack using a nationwide database.

METHODS

A study group enrolled a total of 13,254 patients who were diagnosed with an initial urinary stone attack; a comparison group recruited 39,762 matched non-urinary stone participants during 2003 and 2007. We followed each patient for 3 years to determine new-onset IBS. We also used Cox proportional hazards models to analyze the risk of IBS between the study and comparison groups after modified by demographics, residence, patient characteristics and personal histories.

RESULTS

The occurrence rates of IBS were 3.3% (n = 440) and 2.6% (n = 1,034) respectively in the study and comparison groups. A covariate-adjusted hazard ratio (HR) of IBS in the study group that was 1.28 times greater (HR = 1.29, 95% CI, 1.15-1.44) than that in the comparison group was showed in the stratified Cox proportional analysis. The adjusted HRs of IBS did not decrease after considering demographics and past histories. The majority of IBS (30.5%) occurred within the first 6 months after the stone attack.

CONCLUSION

Patients with an initial urinary stone attack are at increased risk of developing new-onset IBS. The HRs of IBS did not decrease even after adjusting for patient demographics and past histories. Most importantly, 30.5% of IBS occurred within the first 6 months after the urinary stone attack.

Colonic response to laxative ingestion as assessed by MRI differs in constipated irritable bowel syndrome compared to functional constipation

BACKGROUND

Functional constipation (FC) and irritable bowel syndrome with constipation (IBS-C) share many symptoms but underlying mechanisms may be different. We have developed a magnetic resonance imaging (MRI) technique to measure intestinal volumes, transit, and motility in response to a laxative, Moviprep(®) . We aim to use these biomarkers to study the pathophysiology in IBS-C and FC.

METHODS

Twenty-four FC and 24 IBS-C were studied. Transit was assessed using the weighted average position score (WAPS) of five MRI marker pills, taken 24 h before MRI scanning. Following baseline scan, participants ingested 1 L of Moviprep(®) followed by hourly scans. Magnetic resonance imaging parameters and bowel symptoms were scored from 0 to 4 h.

KEY RESULTS

Weighted average position score for FC was 3.6 (2.5-4.2), significantly greater than IBS-C at 2.0 (1.5-3.2), p = 0.01, indicating slower transit for FC. Functional constipation showed greater fasting small bowel water content, 83 (63-142) mL vs 39 (15-70) mL in IBS-C, p < 0.01 and greater ascending colon volume (AC), 314 (101) mL vs 226 (71) mL in IBS-C, p < 0.01. FC motility index was lower at 0.055 (0.044) compared to IBS-C, 0.107 (0.070), p < 0.01. Time to first bowel movement following ingestion of Moviprep(®) was greater for FC, being 295 (116-526) min, compared to IBS-C at 84 (49-111) min, p < 0.01, and correlated with AC volume 2 h after Moviprep(®) , r = 0.44, p < 0.01. Using a cut-off >230 min distinguishes FC from IBS-C with low sensitivity of 55% but high specificity of 95%.

CONCLUSION & INFERENCES

Our objective MRI biomarkers allow a distinction between FC and IBS-C.

The Overlap between Irritable Bowel Syndrome and Non-Celiac Gluten Sensitivity: A Clinical Dilemma

The spectrum of gluten-related disorders has widened in recent times and includes celiac disease, non-celiac gluten sensitivity, and wheat allergy. The complex of symptoms associated with these diseases, such as diarrhea, constipation or abdominal pain may overlap for the gluten related diseases, and furthermore they can be similar to those caused by various other intestinal diseases, such as irritable bowel syndrome (IBS). The mechanisms underlying symptom generation are diverse for all these diseases. Some patients with celiac disease may remain asymptomatic or have only mild gastrointestinal symptoms and thus may qualify for the diagnosis of IBS in the general clinical practice. Similarly, the overlap of symptoms between IBS and non-celiac gluten sensitivity (NCGS) often creates a dilemma for clinicians. While the treatment of NCGS is exclusion of gluten from the diet, some, but not all, of the patients with IBS also improve on a gluten-free diet. Both IBS and NCGS are common in the general population and both can coexist with each other independently without necessarily sharing a common pathophysiological basis. Although the pathogenesis of NCGS is not well understood, it is likely to be heterogeneous with possible contributing factors such as low-grade intestinal inflammation, increased intestinal barrier function and changes in the intestinal microbiota. Innate immunity may also play a pivotal role. One possible inducer of innate immune response has recently been reported to be amylase-trypsin inhibitor, a protein present in wheat endosperm and the source of flour, along with the gluten proteins.

Irritable bowel syndrome: Is it "irritable brain" or "irritable bowel"?

Irritable bowel syndrome (IBS) has been recognized as one of the most common and best studied disorders among the group of functional gastrointestinal disorders. It is a functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit. In the Western world, IBS appears to affect up to 20% of the population at any given time but in Asian countries, the median value of IBS prevalence defined by various criteria ranges between 6.5% and 10.1%, and community prevalence of 4% is found in North India. Those attending gastroenterology clinics represent only the tip of the iceberg. The disorder substantially impairs the quality of life, and the overall health-care costs are high. IBS has therefore gained increased attention from clinicians, researchers, and pharmaceutical industries. It is often frustrating to both patients and physicians as the disease is usually chronic in nature and difficult to treat. However, the understanding of IBS has been changing from time to time and still most of its concepts are unknown. In this review we have discussed, debated, and synthesized the evidence base, focusing on underlying mechanisms in the brain and bowel. We conclude that it is both brain and bowel mechanisms that are responsible. The clinical implication of such mechanisms is discussed.

Predictive factors for the diagnosis of irritable bowel syndrome in a large cohort of 440,822 young adults

BACKGROUND

The prevalence of irritable bowel syndrome (IBS) in the community has been reported in numerous cross-sectional surveys. However, little is known about the incidence and predictive factors for the clinical diagnosis of IBS.

METHODS

We examined the association of socioeconomic, anthropometric, and occupational factors with the incidence of IBS in a cohort of 440,822 young Israeli adults aged 18 to 39 who served in active military service during the years 2005 to 2011.

RESULTS

During the follow-up of 1,925,003 person-years, IBS was diagnosed de novo in 976 patients, giving an incidence rate of 221:100,000 (0.2%) person-years for the diagnosis of IBS. On multivariable Cox analysis, higher socioeconomic status [hazard ratio (HR) 1.629; 95% confidence interval (CI), 1.328-1.999; P<0.0001], Israeli birth (HR 1.362; 95% CI, 1.084-1.712; P=0.008), Jewish ethnicity (HR 2.089; 95% CI, 1.344-3.248; P=0.001), education ≥than 11 years (HR 1.674; 95% CI, 1.019-2.751; P=0.042), and a noncombat military position (HR 1.196; 95% CI, 1.024-1.397; P=0.024) were found to be risk factors for the diagnosis or for the worsening of IBS. Overweight (HR 0.744; 95% CI, 0.589-0.941; P=0.014), obesity (HR 0.698; 95% CI, 0.510-0.95; P=0.025), living in a rural settlement (HR 0.705; 95% CI, 0.561-0.886; P=0.003), and Middle Eastern (HR 0.739; 95% CI, 0.617-0.884; P=0.001,) or North African and Ethiopian origin (HR 0.702; 95% CI, 0.585-0.842; P<0.001) were found to be protective for the diagnosis or the worsening of IBS.

CONCLUSIONS

This study provides novel data on the socioeconomic, anthropometric, and occupational factors predictive for IBS development. The predictive factors for IBS diagnosis may point to the fact that stress had a lower impact on IBS incidence in our study cohort.

Diagnosis of IBS: symptoms, symptom-based criteria, biomarkers or 'psychomarkers'?

IBS is estimated to have a prevalence of up to 20% in Western populations and results in substantial costs to health-care services worldwide, estimated to be US$1 billion per year in the USA. IBS remains difficult to diagnose due to its multifactorial aetiology, heterogeneous nature and overlap of symptoms with organic pathologies, such as coeliac disease and IBD. As a result, IBS often continues to be a diagnosis of exclusion, resulting in unnecessary investigations. Available methods for the diagnosis of IBS-including the current gold standard, the Rome III criteria-perform only moderately well. Visceral hypersensitivity and altered pain perception do not discriminate between IBS and other functional gastrointestinal diseases or health with any great accuracy. Attention has now turned to developing novel biomarkers and using psychological markers (so-called psychomarkers) to aid the diagnosis of IBS. This Review describes how useful symptoms, symptom-based criteria, biomarkers and psychomarkers, and indeed combinations of all these approaches, are in the diagnosis of IBS. Future directions in diagnosing IBS could include combining demographic data, gastrointestinal symptoms, biomarkers and psychomarkers using statistical methods. Latent class analysis to distinguish between IBS and non-IBS symptom profiles might also represent a promising avenue for future research.

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.

A randomised, controlled study of small intestinal motility in patients treated with sacral nerve stimulation for irritable bowel syndrome

Background

Irritable bowel syndrome (IBS) is among the most common gastrointestinal disorders worldwide. In selected patients with severe diarrhoea-predominant or mixed IBS subtypes sacral nerve stimulation (SNS) alleviates IBS-specific symptoms and improves quality of life. The mode of action, however, remains unknown. The present study aimed to evaluate the effect of SNS on small intestinal motility in IBS patients.

Methods

Twenty patients treated with SNS for severe diarrhoea-predominant or mixed IBS were included in a randomised, controlled, crossover study. The neurostimulator was turned ON or OFF for the first one month and then to the opposite setting for the next month. Gastrointestinal transit patterns were investigated with the Motility Tracking System-1 (MTS-1) at the end of each the ON and OFF period. Primary endpoint was change in the velocity of the magnetic pill within the small intestine. Statistical testing was performed with Wilcoxon’s rank sum test and Fisher’s exact test.

Results

The median velocity of the magnetic pill through the small intestine in the fasting state was not significantly different between periods with and without SNS (Group ON-OFF: median change 0 m/h (range -1.07, 0.63), Group OFF-ON: median change 0.27 m/h (range -0.59, 1.12)) (p = 0.25). Neither, was the median velocity of the magnetic pill through the small intestine in the postprandial state significantly different between periods with and without SNS (Group ON-OFF: median change -0.13 m/h (range -0.46, 0.23), Group OFF-ON: median change 0.015 m/h (range -0.48, 0.59)) (p = 0.14).

Conclusion

Even though SNS may reduce symptoms of diarrhoea-predominant and mixed IBS, it has no detectable effect on small intestinal transit patterns.

Trial registration

Clinical.trials.gov, (NCT00919672).

Involvement of interleukin-17A-induced hypercontractility of intestinal smooth muscle cells in persistent gut motor dysfunction

BACKGROUND AND AIM

The etiology of post-inflammatory gastrointestinal (GI) motility dysfunction, after resolution of acute symptoms of inflammatory bowel diseases (IBD) and intestinal infection, is largely unknown, however, a possible involvement of T cells is suggested.

METHODS

Using the mouse model of T cell activation-induced enteritis, we investigated whether enhancement of smooth muscle cell (SMC) contraction by interleukin (IL)-17A is involved in postinflammatory GI hypermotility.

RESULTS

Activation of CD3 induces temporal enteritis with GI hypomotility in the midst of, and hypermotility after resolution of, intestinal inflammation. Prolonged upregulation of IL-17A was prominent and IL-17A injection directly enhanced GI transit and contractility of intestinal strips. Postinflammatory hypermotility was not observed in IL-17A-deficient mice. Incubation of a muscle strip and SMCs with IL-17A in vitro resulted in enhanced contractility with increased phosphorylation of Ser19 in myosin light chain 2 (p-MLC), a surrogate marker as well as a critical mechanistic factor of SMC contractility. Using primary cultured murine and human intestinal SMCs, IκBζ- and p38 mitogen-activated protein kinase (p38MAPK)-mediated downregulation of the regulator of G protein signaling 4 (RGS4), which suppresses muscarinic signaling of contraction by promoting inactivation/desensitization of Gαq/11 protein, has been suggested to be involved in IL-17A-induced hypercontractility. The opposite effect of L-1β was mediated by IκBζ and c-jun N-terminal kinase (JNK) activation.

CONCLUSIONS

We propose and discuss the possible involvement of IL-17A and its downstream signaling cascade in SMCs in diarrheal hypermotility in various GI disorders.

Impact of eating restriction on gastrointestinal motility in adolescents with IBS

OBJECTIVE

Gastrointestinal disturbances as a result of changes in eating patterns have been described in eating disorders. Many patients who experience irritable bowel syndrome report changes in eating patterns as a way to cope with their symptoms. Little is known about the consequences of these practices. The aim of this study was to explore whether repeated eating restriction (defined as not eating ≥ 4 hours while hungry) is associated with motility disturbances.

METHODS

Of 17 patients with irritable bowel syndrome, subjects were divided into those who habitually restrict their eating (n = 8) and those without eating restriction (n = 9) (age range 15-21, mean 19.2; 64.7% girls). Whole-gut transit time was measured by radiopaque markers, gastric sensitivity was measured by water load test (drinking max of 800 mL of water in 5 minutes or until full), and gastric dysrhythmias by an electrogastrogram.

RESULTS

Restrictors drank less water (mean 464.4 mL) than nonrestrictors (mean 613 mL; P = 0.02). No difference was found in gastric dysrhythmias (62.5% vs 77.8%; P = 0.5). Whole-gut transit tended to be slower in the restrictors (mean 51.0 hours) than in nonrestrictors (mean 37.5 hours), but this was not significant.

CONCLUSIONS

Eating restriction appears to be associated with increased gastric sensation. More data are needed from larger studies to determine whether eating behaviors are associated with other motility disturbances.

Fasting and postprandial volumes of the undisturbed colon: normal values and changes in diarrhea-predominant irritable bowel syndrome measured using serial MRI

BACKGROUND

Previous assessments of colon morphology have relied on tests which were either invasive or used ionizing radiation. We aimed to measure regional volumes of the undisturbed colon in healthy volunteers (HV) and patients with diarrhea-predominant irritable bowel syndrome (IBS-D).

METHODS

3D regional (ascending, transverse, and descending) colon volumes were measured in fasting abdominal magnetic resonance (MR) images of 75 HVs and 25 IBS-D patients. Thirty-five of the HV and all 25 IBS-D subjects were fed a standard meal and postprandial MRI data obtained over 225 min.

KEY RESULTS

Colonic regions were identified and 3D maps from cecum to sigmoid flexure were defined. Fasted regional volumes showed wide variation in both HVs being (mean ± SD) ascending colon (AC) 203 ± 75 mL, transverse (TC) 198 ± 79 mL, and descending (DC) 160 ± 86 mL with no difference from IBS-D subjects (AC 205 ± 69 mL, TC 232 ± 100 mL, and DC 151 ± 71 mL, respectively). The AC volume expanded by 10% after feeding (p = 0.007) in the 35 HV possibly due to increased ileo-colonic inflow. A later rise in AC volume occurred from t = 90 to t = 240 min as the meal residue entered the cecum. In contrast, IBS-D subjects showed a much reduced postprandial response of the AC (p < 0.0001) and a greater increase in TC volume after 90 min (p = 0.0244) compared to HV.

CONCLUSIONS & INFERENCES

We have defined a normal range of the regional volumes of the undisturbed colon in fasted and fed states. The AC in IBS-D appeared less able to accommodate postprandial inflow which may account for faster colonic transit.

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.

Prevalence of irritable bowel syndrome-type symptoms in patients with celiac disease: a meta-analysis

BACKGROUND & AIMS

Patients with celiac disease (CD) often report symptoms compatible with irritable bowel syndrome (IBS). However, the prevalence of these symptoms in patients with CD and their relation to adherence to a gluten-free diet (GFD) have not been assessed systematically.

METHODS

We searched MEDLINE, EMBASE, and EMBASE Classic (through July 2012) to identify cross-sectional surveys or case-control studies reporting prevalence of IBS-type symptoms in adult patients (≥ 16 years old) with established CD. The number of individuals with symptoms meeting criteria for IBS was extracted for each study, according to case or control status and adherence to a GFD. Pooled prevalence and odds ratios (ORs), with 95% confidence intervals (CIs), were calculated. We analyzed data from 7 studies with 3383 participants.

RESULTS

The pooled prevalence of IBS-type symptoms in all patients with CD was 38.0% (95% CI, 27.0%-50.0%). The pooled OR for IBS-type symptoms was higher in patients with CD than in controls (5.60; 95% CI, 3.23-9.70). In patients who were nonadherent with a GFD, the pooled OR for IBS-type symptoms, compared with those who were strictly adherent, was 2.69 (95% CI, 0.75-9.56). There was also a trend toward a higher OR for IBS-type symptoms among patients who did not adhere to the GFD, compared with controls (12.42; 95% CI, 6.84-11.75), compared with that observed for adherent CD patients vs controls (4.28; 95% CI, 1.56-11.75).

CONCLUSIONS

IBS-type symptoms occur frequently in patients with CD and are more common than among controls. Adherence to a GFD might be associated with a reduction in symptoms.

Stool characteristics and colonic transit in irritable bowel syndrome: evaluation at two time points

OBJECTIVE

Information on the relationships between stool characteristics and colonic transit time (CTT) in irritable bowel syndrome (IBS) is limited. Our aims were: (i) to relate stool frequency and consistency to total and segmental CTTs, (ii) to correlate changes in these stool characteristics with changes in CTTs between a baseline assessment and a 12-week assessment, and (iii) to examine the confounding effects of mood on these relationships, in patients with IBS.

MATERIALS AND METHODS

Twenty-one female patients with IBS underwent, on two occasions 12 weeks apart, a colonic transit study and completed at these times Bristol Stool Form Scale (BSFS) and Bowel Symptoms Severity Rating Scale (BSSRS). All patients also completed the Hospital Anxiety and Depression scale.

RESULTS

Between baseline and the 12-week assessment, an increase in the number of days over the past week without a bowel motion correlated with prolonged total CTT (r = 0.54, p = 0.01). An increase in the number of days with more than three bowel motions per day correlated with a shorter right CTT (r = -0.52, p = 0.02). Only after adjusting for anxiety and depression, did an increase in loose or watery bowel motions (for BSSRS but not for BSFS) correlate with a shorter right CTT (r = -0.47, p = 0.03).

CONCLUSIONS

Stool frequency, as well as stool consistency, correlates with CTT. Correlations between stool consistency and CTT are more robust for BSSRS than for BSFS. An effect of mood appears to be important in the relationship between stool consistency and CTT.

Anxiety and depression in a sample of Iranian patients with irritable bowel syndrome

OBJECTIVE

Previous studies have shown that up to 50% to 70% of patients with irritable bowel syndrome (IBS) who seek treatment have psychiatric comorbidity. The aim of this study was to report the history of anxiety and depression in IBS patients.

METHODS

The study, designed as a cross-sectional, was performed in a consecutive sample of individuals diagnosed with IBS in the Gastroenterology Clinic of Taleghani Hospital, Tehran province, Iran from October 2010 to October 2011. IBS was diagnosed according to the Rome III criteria. All participants were asked about perceived psychiatric symptoms such as depression and anxiety in the past six months.

RESULTS

153 treatment-seeking IBS patients were entered to the study. The mean age of IBS patients with history of psychiatric symptoms (33.9 years) was relatively lower than those without this history (39.3 years); p< 0.05. There was a significant difference regarding mean age of diarrhea-predominant IBS (IBS-D) patients with history of psychiatric symptoms (26.8 years) and without such history (37.9 years); p< 0.05. However, such a difference was not seen among other types of IBS. The most frequent psychiatric symptoms were reported by the constipation-predominant IBS (IBS-C) patients followed by mixed-IBS (IBS-M) and the least rate was seen in IBS-D.

CONCLUSION

Approximately half of IBS patients reported anxiety and/or depression. IBS-C patients experienced higher proportions of anxiety and depression.

DECLARATION OF INTEREST

None.

Multidomain patient-reported outcomes of irritable bowel syndrome: exploring person-centered perspectives to better understand symptom severity scores

OBJECTIVES

Patient-reported outcomes assessing multiple gastrointestinal symptoms are central to characterizing the therapeutic benefit of novel agents for irritable bowel syndrome (IBS). Common approaches that sum or average responses across different illness components must be unidimensional and have small unique variances to avoid aggregation bias and misinterpretation of clinical data. This study sought to evaluate the unidimensionality of the IBS Symptom Severity Scale (IBS-SSS) and to explore person-centered cluster analytic methods for characterizing multivariate-based patient profiles.

METHODS

Ninety-eight Rome-diagnosed patients with IBS completed the IBS-SSS and a single, global item of symptom severity (UCLA Symptom Severity Scale) at pretreatment baseline of a clinical trial funded by the National Institutes of Health. k-means cluster analyses were performed on participants' symptom severity scores.

RESULTS

The IBS-SSS was not unidimensional. Exploratory cluster analyses revealed four common symptom profiles across five items of the IBS-SSS. One cluster of patients (25%) had elevated scores on pain frequency and bowel dissatisfaction, with less elevated but still high scores on life interference and low pain severity ratings. A second cluster (19%) was characterized by intermediate scores on both pain dimensions but more elevated scores on bowel dissatisfaction. A third cluster (18%) had elevated scores across all IBS-SSS subcomponents. The fourth and the most common cluster (37%) had relatively low scores on all dimensions except bowel dissatisfaction and life interference due to IBS symptoms.

CONCLUSIONS

Patient-reported outcome end points and research on IBS more generally relying on multicomponent assessments of symptom severity should take into account the multidimensional structure of symptoms to avoid aggregation bias and to optimize the sensitivity of detecting treatment effects.

Irritable bowel syndrome: Diagnosis and pathogenesis

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder that considerably reduces the quality of life. It further represents an economic burden on society due to the high consumption of healthcare resources and the non-productivity of IBS patients. The diagnosis of IBS is based on symptom assessment and the Rome III criteria. A combination of the Rome III criteria, a physical examination, blood tests, gastroscopy and colonoscopy with biopsies is believed to be necessary for diagnosis. Duodenal chromogranin A cell density is a promising biomarker for the diagnosis of IBS. The pathogenesis of IBS seems to be multifactorial, with the following factors playing a central role in the pathogenesis of IBS: heritability and genetics, dietary/intestinal microbiota, low-grade inflammation, and disturbances in the neuroendocrine system (NES) of the gut. One hypothesis proposes that the cause of IBS is an altered NES, which would cause abnormal GI motility, secretions and sensation. All of these abnormalities are characteristic of IBS. Alterations in the NES could be the result of one or more of the following: genetic factors, dietary intake, intestinal flora, or low-grade inflammation. Post-infectious IBS (PI-IBS) and inflammatory bowel disease-associated IBS (IBD-IBS) represent a considerable subset of IBS cases. Patients with PI- and IBD-IBS exhibit low-grade mucosal inflammation, as well as abnormalities in the NES of the gut.

Global prevalence of and risk factors for irritable bowel syndrome: a meta-analysis

BACKGROUND & AIMS

Many cross-sectional surveys have reported the prevalence of irritable bowel syndrome (IBS), but there have been no recent systematic review of data from all studies to determine its global prevalence and risk factors.

METHODS

MEDLINE, EMBASE, and EMBASE Classic were searched (until October 2011) to identify population-based studies that reported the prevalence of IBS in adults (≥15 years old); IBS was defined by using specific symptom-based criteria or questionnaires. The prevalence of IBS was extracted for all studies and based on the criteria used to define it. Pooled prevalence, according to study location and certain other characteristics, odds ratios (ORs), and 95% confidence intervals (CIs) were calculated.

RESULTS

Of the 390 citations evaluated, 81 reported the prevalence of IBS in 80 separate study populations containing 260,960 subjects. Pooled prevalence in all studies was 11.2% (95% CI, 9.8%-12.8%). The prevalence varied according to country (from 1.1% to 45.0%) and criteria used to define IBS. The greatest prevalence values were calculated when ≥3 Manning criteria were used (14%; 95% CI, 10.0%-17.0%); by using the Rome I and Rome II criteria, prevalence values were 8.8% (95% CI, 6.8%-11.2%) and 9.4% (95% CI, 7.8%-11.1%), respectively. The prevalence was higher for women than men (OR, 1.67; 95% CI, 1.53-1.82) and lower for individuals older than 50 years, compared with those younger than 50 (OR, 0.75; 95% CI, 0.62-0.92). There was no effect of socioeconomic status, but only 4 studies reported these data.

CONCLUSIONS

The prevalence of IBS varies among countries, as well as criteria used to define its presence. Women are at slightly higher risk for IBS than men. The effects of socioeconomic status have not been well described.

Rifaximin therapy of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by abdominal pain and altered bowel habits in the absence of specific organic pathology. Although the underlying pathogenesis of IBS is not well-understood, small intestinal bacterial overgrowth (SIBO) or other abnormalities in the gut flora is believed to contribute to the development of a subset of IBS cases. Rifaximin is a poorly absorbed antimicrobial with activity against enteric pathogens. A number of studies have shown a significant improvement in IBS symptoms with antibiotic therapy including rifaximin. In this review, we discuss the pharmacokinetics, in vitro susceptibility profile, and efficacy and safety data from clinical trials of rifaximin treatment of IBS.

Functional abdominal bloating with distention

Ten to 25% of healthy persons experience bloating. It is particularly common in persons with the irritable bowel syndrome and constipation. While the cause of bloating remains unknown old explanations such as a excessive intestinal gas, exaggerated lumbar lordosis and psychiatric problems have been disproved. New suggestions include recent weight gain, weak or inappropriately relaxed abdominal muscles, an inappropriately contracted diaphragm and retained fluid in loops of distal small bowel. No treatment is of unequivocal benefit but a low FODMAPs diet, probiotics and the non-absorbable antibiotic rifaximin offer some hope. Treatment by weight loss, abdominal exercise, prokinetics and girdles need more study.

Colonic transit time and IBS symptoms: what's the link?

OBJECTIVES

The relevance of colonic transit alterations for the overall symptom pattern in irritable bowel syndrome (IBS) is incompletely understood. The aim of this study was to assess the total and segmental colonic transit time (CTT) and their relationship to symptoms and subgroups in a large sample of IBS patients.

METHODS

Total and segmental CTT was assessed using radiopaque markers in 359 patients with IBS (279 females). These results were compared with existing normal values for healthy men and women without gastrointestinal (GI) symptoms. Stool frequency and consistency (Bristol Stool Form (BSF) scale), and the perceived severity of three GI symptoms (bloating, flatulence, and abdominal pain) were noted in a daily diary during the measurement week. Patients could be classified by the BSF scale characteristics into Rome III subtypes (n=338), or by use of the Rome II modular questionnaire into Rome II subtypes (n=143).

RESULTS

CTT was normal in 287 patients (80%), whereas 53 (15%) had accelerated and 19 (5%) had delayed CTT. Transit abnormalities in relation to gender-specific reference values were more common in males (30.0%) than in females (17.2%; P < 0.05). IBS subgrouping according to Rome III (P < 0.0001) and Rome II criteria (P < 0.001) was associated with the presence of abnormal CTT. Stool form (r=-0.40; P < 0.0001) and stool frequency (r=-0.30; P<0.0001) were moderately and negatively correlated to total CTT. No correlations of clinical significance were found between transit data and the three GI symptoms.

CONCLUSIONS

Total and segmental colonic transit alterations are of importance for the abnormal bowel habit seen in men and women with IBS, but of no or minor importance for other IBS symptoms.

Low densities of serotonin and peptide YY cells in the colon of patients with irritable bowel syndrome

BACKGROUND

The gut hormones are important in regulating gastrointestinal motility. Disturbances in gastrointestinal motility have been reported in patients with irritable bowel syndrome (IBS). Reduced endocrine cell density, as revealed by chromogranin A, has been reported in the colon of IBS patients.

AIMS

To investigate a possible abnormality in the colonic endocrine cells of IBS patients.

METHODS

A total of 41 patients with IBS according to Rome Criteria III and 20 controls were included in the study. Biopsies from the right and left colon were obtained from both patients and controls during colonoscopy. The biopsies were immunostained for serotonin, peptide YY (PYY), pancreatic polypeptide (PP), entroglucagon, and somatostatin cells. Cell densities were quantified by computerized image analysis.

RESULTS

Serotonin and PYY cell densities were reduced in the colon of IBS patients. PP, entroglucagon, and somatostatin-immunoreactive cells were too few to enable reliable quantification.

CONCLUSION

The cause of these observations could be primary genetic defect(s), secondary to altered serotonin and/or PYY signaling systems and/or subclinical inflammation. Serotonin activates the submucosal sensory branch of the enteric nervous system and controls gastrointestinal motility and chloride secretion via interneurons and motor neurons. PYY stimulates absorption of water and electrolytes, and inhibits prostaglandin (PG) E2, and vasoactive intestinal peptide, which stimulates intestinal fluid secretion and is a major regulator of the "ileal brake". Although the cause and effect relationship of these findings is difficult to elucidate, the abnormalities reported here might contribute to the symptoms associated with IBS.

Gastrointestinal pH profile in subjects with irritable bowel syndrome

AIM

To investigate the small bowel pH profile and small intestine transit time (SITT) in healthy controls and patients with irritable bowel syndrome (IBS).

METHODS

Nine IBS patients (3 males, mean age 35 yr) and 10 healthy subjects (6 males, mean age 33 yr) were studied. Intestinal pH profile and SITT were assessed by a wireless motility pH and pressure capsule (Smart Pill). Mean pH values were measured in the small intestine (SI) and compared both within and between groups. Data presented as mean or median, ANOVA, P <0.05 for significance.

RESULTS

We found the pH for the first (Q1), second (Q2), third (Q3), and fourth quartile (Q4) of the SI in healthy versus IBS patients was 5.608 ± 0.491 vs. 5.667 ± 0.297, 6.200 ± 0.328 vs. 6.168 ± 0.288, 6.679 ± 0.316 vs. 6.741 ± 0.322, and 6.884 ± 0.200 vs. 6.899 ± 0.303, respectively. We found no significant group difference in pH per quartile (P=0.7979). The proximal SI was significantly more acidic, compared to distal segments, in both healthy subjects and IBS patients (P<0.0001). We found no significant difference in the measured SITT between IBS and control groups with a mean SITT of 218.56 ± 59.60 min and 199.20 ± 82.31 min, respectively (P=0.55).

CONCLUSION

This study shows the presence of a gradient of pH along the SI, in both IBS and healthy subjects, the distal being less acidic. These finding may be of importance in small bowel homeostasis.

Pathophysiology, evaluation, and treatment of bloating: hope, hype, or hot air?

Abdominal bloating is commonly reported by men and women of all ages. Bloating occurs in nearly all patients with irritable bowel syndrome, and it also occurs in patients with other functional and organic disorders. Bloating is frequently disturbing to patients and frustrating to clinicians, as effective treatments are limited and are not universally successful. Although the terms bloating and abdominal distention are often used interchangeably, these symptoms likely involve different pathophysiologic processes, both of which are still not completely understood. The goal of this paper is to review the pathophysiology, evaluation, and treatment of bloating and abdominal distention.

Magnetic resonance imaging of rectal volume in patients with irritable bowel syndrome

BACKGROUND

Extreme stool forms (1 and 2, or 6 and 7 of the Bristol stool scale) are frequent in patients with irritable bowel syndrome and are associated with colonic transit, but it is not known whether these alterations influence rectal reservoir function.

AIMS

To investigate rectal reservoir function by assessing magnetic resonance imaging reconstructions of rectal volume in healthy subjects and patients with irritable bowel syndrome, and to establish whether it varies depending on the bowel habits of the patients.

METHODS

Twelve healthy subjects and 20 patients with irritable bowel syndrome (with constipation, diarrhoea, mixed or undefined bowel habit according to the Rome III criteria) underwent pelvic magnetic resonance imaging in the absence of rectal sensations. T2 sagittal images were used to calculate rectal volume by multiplying inter-slice thickness by rectal area, and summing the inter-slice volumes.

RESULTS

Stool form was significantly different in the irritable bowel syndrome patients with diarrhoea or constipation, and bowel movements were more frequent in the irritable bowel syndrome patients than in the healthy subjects. Rectal volume was significantly smaller in the irritable bowel syndrome patients (27 ± 13 mL vs. 44 ± 21 mL; P=0.04), with no significant differences between the bowel habit sub-types.

CONCLUSION

The reduced rectal volume in irritable bowel syndrome patients suggests that rectal tone is increased and that, at least in the absence of rectal sensations, the rectum is not over-distended by stools.

Mucosal inflammation as a potential etiological factor in irritable bowel syndrome: a systematic review

BACKGROUND

The causes of irritable bowel syndrome (IBS) remain obscure. Some investigators have proposed chronic low-grade mucosal inflammation as a potential etiological factor. We performed a systematic review to examine this issue in detail.

METHODS

MEDLINE, EMBASE, and EMBASE classic were searched up to December 2010 to identify studies of case-control design applying tests for low-grade inflammation to either full-thickness intestinal or endoscopic mucosal biopsies from patients with IBS. Controls were required to be healthy individuals, or asymptomatic patients undergoing investigation for reasons other than the reporting of upper or lower gastrointestinal symptoms. Individual study results were summarized descriptively.

RESULTS

The literature search identified 1388 citations, of which 16 studies were eligible for inclusion. Individual study results were diverse, partly as a consequence of the different surrogate markers for inflammatory mechanisms studied. Mast cells, T lymphocytes, B lymphocytes, and mucosal cytokine production all appeared altered among cases with IBS in individual studies, while no study demonstrated a significant difference in numbers of plasma cells, neutrophils, or eosinophils. Some studies suggested a relationship between mast cell abnormalities and symptom severity and frequency, as well as co-existent fatigue and depression. Studies were limited by the lack of comparability of controls, and the fact that most were conducted in highly selected groups of patients with IBS.

CONCLUSIONS

Low-grade mucosal inflammation, particularly mast cell activation, may be a contributory factor in the pathogenesis of IBS. Mast cell stabilizers warrant further assessment as a potential therapy in the condition.

Existing and emerging therapies for irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome is a common disorder that is associated with a significant impact on both affected individuals and society. While the pathophysiology of irritable bowel syndrome remains unknown, knowledge regarding the normal and abnormal functions of the gut and its complex interaction with the body's nervous systems continues to shed light on the multifactorial origins of irritable bowel syndrome symptoms. This article provides an overview of the current knowledge of the therapeutic approaches to irritable bowel syndrome.

AREAS COVERED

A search of the online bibliographic databases MEDLINE and EMBASE was performed in order to identify all relevant articles published between 1980 and 2010. The search was enhanced with the use of a medical librarian. Bibliographies from potentially relevant articles were manually searched.

EXPERT OPINION

The therapeutic options for irritable bowel syndrome are rapidly evolving beyond traditional symptom-based therapies, such as fiber, antispasmodics, antidiarrheals and laxatives, and are moving toward agents with organ-specific receptor selectivity directed, in many cases, at specific gastrointestinal functions.

Peripherally acting therapies for the treatment of irritable bowel syndrome

Gut-acting therapies are common therapies for irritable bowel syndrome (IBS). Most of these peripheral acting agents are primarily targeted at individual symptoms. The evidence supporting the use of these agents in IBS is largely anecdotal. Serotonergic agents and the chloride channel activator lubiprostone have shown efficacy in treating symptoms of IBS. The clinical evidence supporting the use of these agents is based on data from high-quality clinical trials. The use of serotonergic agents for IBS in the United States is limited to the 5-hydroxytryptamine-3 antagonist alosetron in the treatment of women with severe IBS with diarrhea refractory to traditional therapy.

The role of experimental models in developing new treatments for irritable bowel syndrome

Irritable bowel syndrome (IBS) is characterized by chronic, recurrent abdominal pain and altered bowel habits and is currently defined by symptom criteria and the absence of detectable organic disease. The underlying pathophysiology remains incompletely understood. Despite considerable efforts by the scientific community and the pharmaceutical industry to develop novel pharmacological treatments aimed at chronic visceral pain, the traditional approach to identifying and evaluating novel drugs for this target have largely failed to translate into effective IBS treatments. However, several novel drugs aimed at normalizing bowel movements have produced clinical effects, not only on the primary target, but also on pain and discomfort. While some of the commonly used experimental animal models for the pain dimension of IBS have some face and construct validity, the predictive validity of most of the models is either unknown, or has been disappointing. A reverse translational approach is proposed, which is based on identification and characterization of brain endophenotypes in patients, followed by translation of these endophenotypes for pharmacological studies in rodent models.

Proteomic analysis of colonic mucosa in a rat model of irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common functional disorders of the gastrointestinal tract. It is characterized by abdominal pain and changes in bowel habits. Various studies have investigated the pathophysiologic processes underlying IBS, but the mechanism remains poorly understood. In the present study, we established an IBS model and identified differentially expressed proteins in colon tissue of IBS rats compared with healthy controls by 2-D gel electrophoresis, MALDI-TOF-MS, and Western blot analysis. Our results showed that 13 of the 1396 protein spots on 2-D gel were differently expressed between the IBS and control groups. Ontological analysis of these proteins revealed primary roles in catalytic activity (protein disulfide-isomerase A3, glyoxalase I, cathepsin S, alpha-enolase), structural support (cytokeratin 8), antioxidant activity (peroxiredoxin-6), protein binding (transgelin, serpin peptidase inhibitor B5), and signal transduction (40S ribosomal protein SA). Protein disulfide-isomerase A3 and cytokeratin 8 overexpression in IBS were confirmed by Western blot. The findings indicate that multiple proteins are involved in IBS processes that influence intestinal tract immunity, inflammation, and nerve regulation. Our study provides useful candidate genes and proteins for further investigation.

Abnormal small-intestinal endocrine cells in patients with irritable bowel syndrome

BACKGROUND

General disturbances in gastrointestinal motility have been reported in patients with irritable bowel syndrome (IBS). The gastrointestinal tract hormones play an important role in regulating gastrointestinal motility.

AIMS

To investigate a possible abnormality in the small intestinal endocrine cells of IBS patients.

METHODS

Included in the study were 41 patients with irritable bowel syndrome according to Rome Criteria III and 42 healthy controls. Duodenal biopsies were obtained from both patients and controls during gastroscopy. The biopsies were immunostained by avidin-biotin-complex method for secretin, CCK, GIP, somatostatin, and serotonin cells. The cell densities were quantified by computerized image analysis.

RESULTS

The density of secretin- and CCK-immunoreactive cells in patients with IBS was significantly reduced. The reduction in secretin and CCK cells occurred only in IBS-diarrhea patients, but not in IBS-constipation subtype. Both GIP and somatostatin cell densities were reduced in the duodenum of IBS patients. There was no statistical difference between the subtypes of IBS patients, regarding secretin, CCK, GIP, or somatostatin cell densities. Serotonin cell density was not affected in patients with IBS.

CONCLUSIONS

The low densities of secretin and CCK cells in IBS-diarrhea patients may cause a functional pancreatic insufficiency as well as inadequate gall emptying, as these hormones stimulate pancreatic bicarbonate and enzyme secretion and CCK stimulates as well gall bladder contraction. Low densities of secretin, GIP, and somatostatin cells in IBS patients might result in a high secretion of gastric acid, as secretin, GIP, and somatostatin inhibit gastric acid secretion.

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.

Systematic review and meta-analysis of the prevalence of irritable bowel syndrome in individuals with dyspepsia

BACKGROUND & AIMS

Dyspepsia and irritable bowel syndrome (IBS) are common conditions that can coexist in patients. We performed a systematic review and meta-analysis to estimate prevalence of IBS in dyspepsia.

METHODS

Relevant articles published through August 2008 were identified from MEDLINE and EMBASE literature searches (23,457 citations). Eligible studies included adults recruited from the community, the workplace, blood donation or screening clinics, and family physician offices or internal medicine clinics. Selected studies reported prevalence of dyspepsia and IBS within the same population. The prevalence of IBS in subjects with and without dyspepsia was pooled for all studies and compared. Odds ratios (OR) and confidence intervals (CI) were calculated. The degree of overlap between dyspepsia and IBS was determined.

RESULTS

Of 239 papers evaluated, 150 reported prevalence of dyspepsia and 19 (involving 18,173 subjects) reported the proportion of subjects with IBS within the same population. The prevalence of dyspepsia was 27% (95% CI, 23%-31%). The prevalence of IBS in subjects with dyspepsia was 37% (95% CI, 30%-45%) compared with 7% (95% CI, 5%-10%) in those without. The pooled OR for IBS in subjects with dyspepsia was 8 (95% CI, 5.74-11.16). The degree of overlap between the 2 conditions varied from 15% to 42%, depending on diagnostic criteria used for each.

CONCLUSIONS

Individuals with dyspepsia have an 8-fold increase in prevalence of IBS compared with the population. The strength of the association suggests common pathogenic mechanisms. Dyspeptic patients should be assessed routinely for IBS.

Asian motility studies in irritable bowel syndrome

Altered motility remains one of the important pathophysiologic factors in patients with irritable bowel syndrome (IBS) who commonly complain of abdominal pain and stool changes such as diarrhea and constipation. The prevalence of IBS has increased among Asian populations these days. Gastrointestinal (GI) physiology may vary between Asian and Western populations because of differences in diets, socio-cultural backgrounds, and genetic factors. The characteristics and differences of GI dysmotility in Asian IBS patients were reviewed. MEDLINE search work was performed including following terms, 'IBS,' 'motility,' 'transit time,' 'esophageal motility,' 'gastric motility,' 'small intestinal motility,' 'colonic motility,' 'anorectal function,' and 'gallbladder motility' and over 100 articles were categorized under 'esophagus,' 'stomach,' 'small intestine,' 'colon,' 'anorectum,' 'gallbladder,' 'transit,' 'motor pattern,' and 'effect of stressors.' Delayed gastric emptying, slow tansit in constipation predominant IBS patients, rapid transit in diarrhea predominant IBS patients, accelerated motility responses to various stressors such as meals, mental stress, or corticotrophin releasing hormones, and altered rectal compliance and altered rectal accomodation were reported in many Asian studies regarding IBS. Many conflicting results were found among these studies and there are still controversies to conclude these as unique features of Asian IBS patients. Multinational and multicenter studies are needed to be performed vigorously in order to elaborate characteristics as well as differences of altered motililty in Asian patients with IBS.