A142 APPROPRIATENESS OF POST-ENDOSCOPY CARE IN PATIENTS PRESENTING WITH FOOD BOLUS IMPACTIONS OVERNIGHT: A POPULATION-BASED MULTICENTER COHORT STUDY

Background

Appropriate management of esophageal food bolus impactions includes endoscopic evaluation and follow-up for potential underlying esophageal pathology. Patients who present with impactions at night may not receive optimal long-term post-endoscopy care due to patient-, physician-, or system-related factors.

Purpose

We aimed to evaluate the appropriateness of care for patients who present with food bolus impactions after regular daytime hours.

Method

We conducted a retrospective, population-based, multi-center cohort study of adult patients undergoing endoscopy for food impaction between 19:00-06:59 from 2016-2018 in the Calgary Health Zone, Canada. Appropriate post-endoscopy care was defined by a composite of a follow-up clinic visit, repeat endoscopy, other appropriate investigations (e.g., manometry), or appropriate medical treatment (e.g., proton pump inhibitor). Predictors of inappropriate care were assessed using multivariable logistic regression, expressed as adjusted odds ratios (aOR) with 95% confidence intervals (CI).

Result(s)

A total of 323 patients underwent an after-hours or overnight endoscopy for food bolus impaction. 25.4% (82/323) of patients did not receive appropriate post-endoscopy care. Predictors of inappropriate care included rural residence (aOR 2.66 [95% CI: 1.18-6.01], p=0.02), first food bolus presentation (aOR 2.38 [95% CI: 1.04-5.44], p=0.04), and absence of a specific pathology during the index procedure (aOR 3.01 [95% CI: 0.97-9.29], p=0.05), suggesting a potential association with clinician cognitive bias. Among patients who were followed, 18.9% (35/185) had a change in the original diagnosis.

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Conclusion(s)

One quarter of patients presenting with a food bolus impaction at night do not receive appropriate post-endoscopy care. System-based interventions should target this high-risk population as the diagnosis and management may change with follow-up.

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Disclosure of Interest

None Declared

A134 UES MANOMETRIC PARAMETERS IN ESOPHAGEAL MOTILITY DISORDERS

Background

Upper esophageal sphincter (UES) function may be evaluated manometrically using a solid-state high-resolution manometry (HRM) system, which allows for the measurement of manometric parameters specific to the UES. While many of these parameters have yet to be validated for use in clinical practice, there is some suggestion that there may be an association between esophageal motility and UES function.

Aims

We aimed to identify the relationship between UES manometric variables and high-resolution esophageal manometry (HREM) diagnoses.

Methods

A retrospective analysis of HREM studies was performed between 2019 and 2021. Extraction of esophageal and UES manometric variables were performed. UES manometric values of interest included: mean basal pressure (mmHg), mean residual pressure (mmHg), relaxation time-to-nadir (ms), relaxation duration (ms), and recovery time (ms). Relationships between manometric diagnosis (Chicago Classification version 3) and UES manometric variables were explored. All values are expressed a medians and group means were compared with the non-parametric Mann-Whitney U test.

Results

2119 symptomatic patients underwent HREM over the study period. Manometric diagnoses were achalasia (72 patients), esophagogastric junction outflow obstruction (286), absent contractility (108), distal esophageal spasm (53), jackhammer esophagus (32), and ineffective esophageal motility (694). 886 patients had no specific motility disorder; 643 of whom had ≤ 20% ineffective swallows and were considered symptomatic controls.

Patients with achalasia had significantly higher mean basal pressures (63.2 vs. 54.4, p = .001), mean residual pressure (3.8 vs. -1.9, p < .001), relaxation-time-to-nadir (182.0 vs. 142.0, p = .005), relaxation duration (820.5 vs. 708.0, p < .001) and recovery time (623.0 vs. 562, p < .001) compared to control patients. Among patients with achalasia, the presence of panesophageal pressurization correlated weakly with recovery time (R² .3, p = .03). Patients with ineffective esophageal motility had significantly higher mean basal pressures (61.7 vs. 54.0, p < .001).

Among all patients, patients with incomplete bolus clearance (≥ 30%) had significantly higher UES mean basal pressure (58.9 vs. 54.6, p = .004), mean residual pressure (-.62 vs. -2, p < .001), relaxation duration (724.0 vs. 707.0, p = .014) and recovery time (580 vs. 558.0, p < .001).

Conclusions

Patients with achalasia may have higher basal and residual UES pressures, and slower relaxation compared to patients with normal esophageal motility. This may reflect dynamic changes of the UES in response to obstruction at the esophagogastric junction. Elevated UES pressures are also seen in patients with ineffective esophageal motility, potentially reflecting a response to poor bolus clearance. More work needs to be done to validate these parameters in clinical practice.

Funding Agencies

None

A97 DEVELOPMENT OF PREDICTION MODELS FOR THE TRIAGING OF REFERRALS OF INDIVIDUALS WITH SUSPECTED INFLAMMATORY BOWEL DISEASE TO IMPROVE PROMPT ACCESS TO CARE

Background

The negative impact of a delayed inflammatory bowel disease (IBD) diagnosis has been well established. We created a clinical pathway referred to as the “High-Risk IBD clinic” within a centralized referral program in a tertiary referral centre, in order to improve access to subspecialist care for individuals suspected but not yet diagnosed with IBD. Despite the creation of this specialized clinic, wait times continue to be above the recommended benchmarks established by the Canadian Association of Gastroenterology (CAG).

Aims

The purpose of our study was to create predictive models to identify factors associated with an IBD diagnosis in order to improve triage of referrals of individuals with features highly suggestive of IBD. We hypothesized that features suggestive of IBD could be used to create discriminating prediction models between IBD and IBS.

Methods

We conducted a retrospective cohort study of referrals to the High-Risk IBD clinic from February 2014 to December 2018. Referral information, investigations, endoscopic findings and final diagnosis were obtained from 316 consented individuals. Information required included symptoms (e.g. diarrhea, abdominal pain, rectal bleeding), risk factors (e.g. family history, rheumatological disease) and investigations (e.g. hemoglobin, CRP, abdominal imaging). Univariate logistic regression was performed to explore the association between factors included in the referral form, and a diagnosis of Crohn’s disease (CD) and ulcerative colitis (UC). For creation of predictive models, any variable with a p-value of <0.1 in univariate logistic regression was selected for entry into the multivariate model for CD and UC.

Results

For UC, the predictive model included weight loss, the presence of rectal bleeding and abdominal pain. Using these criteria, the sensitivity and specificity of the model were 62.5% and 74.1%, respectively. The negative predictive value (NPV) was high at 94.2%. For CD, the predictive model included male gender, elevated CRP, presence of anemia and presence of weight loss. The sensitivity and specificity of this model were 61.7% and 71.2%, respectively. As for UC, the NPV was also high (89.2%). For IBS, the most common diagnosis encountered in patients referred to the HR-IBD clinic, the model included absence of weight loss, presence of abdominal pain and female gender. The sensitivity and specificity were 71.6% and 64.0%, respectively. The positive predictive value was 60.6% and NPV was 74.5%.

Conclusions

We established predictive tools associated with a final diagnosis of IBD and IBS as a means to expedite the care of individuals with undiagnosed IBD.

Funding Agencies

CCC

A247 MEDITATION AND YOGA FOR IRRITABLE BOWEL SYNDROME (MY-IBS): A RANDOMIZED CONTROLLED TRIAL

Background

When delivered in person, yoga is effective in managing Irritable Bowel Syndrome (IBS) symptoms. However, research is needed to determine the feasibility and effectiveness of yoga as a therapeutic option when delivered virtually.

Aims

The aim was to explore the feasibility and effectiveness of a yoga program, delivered virtually, for patients with IBS. We hypothesized the program would be feasible and effective in improving outcomes in the intervention group compared to the control group.

Methods

Adults diagnosed with IBS were randomized to receive either a Hatha yoga intervention or to an advice-only control group. The intervention consisted of facilitator-led weekly online classes for eight weeks delivered using Microsoft Office Teams and daily home practice. Yoga sessions included sequential delivery of postures, chanting, breathing exercises, and meditation over four weeks, with integrated practice over the final four weeks. Feasibility was evaluated with recruitment and attrition rates, adherence, and safety. The primary outcome was severity of IBS symptoms (IBS-Symptom Severity Score, IBS-SSS). Secondary outcomes included anxiety (General Anxiety Disorder-7), depression (Patient Health Questionnaire-9), and stress (Perceived Stress Scale) assessed at baseline and eight weeks. Unadjusted and adjusted analysis of variance (and covariance) models compared baseline and post-intervention data between groups using intent to treat analysis.

Results

Sixty-five participants participated (32 treatment, 33 control). The mean age was 44.2±14.1 years and 91% identified as female. Participants had been living with IBS for 11.7±11 years. Fifteen participants were lost to follow-up (20% attrition rate). Participants attended on average 5.9±1.7 out of a possible 8 sessions (74% adherence) and accumulated 1,187±545 minutes in daily practice over eight weeks. No adverse events were reported. The groups did not differ at baseline (P>0.05). From baseline to post intervention, unadjusted ANOVA models indicated the yoga program was not statistically superior to the control group for IBS-symptoms (-17.5 points; 95% CI -62.6 to 27.6; P = 0.440), anxiety (-0.91 points; 95% CI -2.47 to 0.64; P = 0.245) and stress (-0.65 points; 95% CI -1.73 to 0.44; P = 0.239). Significant differences between groups were seen for depression (-1.82 points; 95% CI -3.49 to -0.15; P = 0.033). A second model considered relevant covariates including age, comorbidities, and years since diagnosis (i.e., ANCOVA), and the results were similar to the unadjusted model.

Conclusions

Our virtual Hatha yoga and mediation program was feasible, and participants showed improvement in their depression scores. However, they did not experience a significant improvement in their IBS symptoms, anxiety, or stress, perhaps due to the short timeframe of the intervention.

Funding Agencies

None

Genome-wide insights of Ethiopian indigenous sheep populations reveal the population structure related to tail morphology and phylogeography

BACKGROUND

Ethiopian sheep living in different climatic zones and having contrasting morphologies are a most promising subject of molecular-genetic research. Elucidating their genetic diversity and genetic structure is critical for designing appropriate breeding and conservation strategies.

OBJECTIVE

The study was aimed to investigate genome-wide genetic diversity and population structure of eight Ethiopian sheep populations.

METHODS

A total of 115 blood samples were collected from four Ethiopian sheep populations that include Washera, Farta and Wollo (short fat-tailed) and Horro (long fat-tailed). DNA was extracted using Quick-DNA™ Miniprep plus kit. All DNA samples were genotyped using Ovine 50 K SNP BeadChip. To infer genetic relationships of Ethiopian sheep at national, continental and global levels, genotype data on four Ethiopian sheep (Adilo, Arsi-Bale, Menz and Black Head Somali) and sheep from east, north, and south Africa, Middle East and Asia were included in the study as reference.

RESULTS

Mean genetic diversity of Ethiopian sheep populations ranged from 0.352 ± 0.14 for Horro to 0.379 ± 0.14 for Arsi-Bale sheep. Population structure and principal component analyses of the eight Ethiopian indigenous sheep revealed four distinct genetic cluster groups according to their tail phenotype and geographical distribution. The short fat-tailed sheep did not represent one genetic cluster group. Ethiopian fat-rump sheep share a common genetic background with the Kenyan fat-tailed sheep.

CONCLUSION

The results of the present study revealed the principal component and population structure follows a clear pattern of tail morphology and phylogeography. There is clear signature of admixture among the study Ethiopian sheep populations.

A129 THE VALUE OF REPEAT MANOMETRIC TESTING

Background

While motility disorders may evolve over time, there is scant guidance around the role of repeat high-resolution esophageal manometry (HRM). Given the invasive nature of HRM and the implications on financial cost and patient discomfort, it is obvious that the emphasis should be on minimizing unnecessary repeat examinations. However, there are no recommendations around indications or timing of repeat HRM.

Aims

We aimed to determine the outcomes in patients who underwent repeat manometry and look for predictors of progression to achalasia or major motility disorder.

Methods

Consecutive reports from HRM studies performed between Aug 2013 – May 2017 were retrospectively analyzed. All patients with ≥ 2 HRM studies were included. Studies without a Chicago classification diagnosis were excluded. Chi-squared analysis was performed to determine if initial HRM diagnosis was associated with change in diagnosis on follow-up HRM. Initial and follow-up manometric parameters were compared with paired T-tests. Binary logistic regression analysis was performed to look for predictors of progression to achalasia or major motility disorder.

Results

134 patients underwent ≥ 2 HRM studies. Initial diagnoses were IEM (45 patients [33.6%], EGJOO (34 [25.4%], absent peristalsis (18 [13.4%], achalasia (11 [8.2%], DES (4 [3.0%]), and JH (3 [2.2%]; 29 (14.2%) of patients had a normal HRM. 109 (81.3%) patients underwent 2 HRM, 18 (13.4%) 3 HRM, 4 (3%) 4 HRM, and 3 (2.2%) 5 HRM.

The final follow-up HRM occurred after a median 496 [80 – 1823] days. 72 (53.7%) of patients had no change from their initial diagnosis. Patients with an initial diagnosis of DES were significantly more likely to have a change in diagnosis on the final follow-up (3 normal:1 IEM) (p = .043). No other classes reached significance. Patients with IEM had a significantly higher mean DCI (395.1 [0 - 3248] vs 790.8 [0 – 10715.0], p = .006) and IRP (4.5 [-10.4 – 14.2] vs [6.6 [-6.2 – 21.0], p = .017) on their follow-up HRM.

4 patients without achalasia (3 EGJOO:1 IEM) on their index HRM had a diagnosis of achalasia on their final HRM. The median IRP in non-achalasia patients with a diagnosis of achalasia on final HRM (22.3 [8.4 – 30.7] was significantly higher than those without a diagnosis of achalasia on final HRM (6.6 [-10.4 – 39.8]) (p = .013); however no manometric criteria or initial HRM diagnoses predicted progression to achalasia or major motility disorder on binary logistic regression analysis.

Conclusions

In most patients, repeat manometry did not change the manometric diagnosis. Patients with DES were significantly likely to have their diagnosis change with repeat HRM, and most of these patients had normalization of their HRM. Manometric parameters in IEM appear to improve over time. This finding could reflect interval therapy, or shed some light on the natural history of this disease.

Funding Agencies

None

A150 ACCESS TIMES TO GASTROENTEROLOGY FOR HIGH-RISK IBD REFERRALS IN THE GREATER CALGARY REGION

Background

Delay in the diagnosis of inflammatory bowel disease (IBD) can lead to adverse outcomes. In 2006, the CAG Wait Time Consensus Group recommended that wait times for patients with symptoms highly suggestive of IBD should be seen within two weeks. In 2007, the greater Calgary region established a central access and triage system to improve access to care as well as the “High-Risk IBD clinic” (HR-IBD) to further expedite the access of patients with IBD alarm symptoms. These included diarrhea, rectal bleeding, weight loss, abnormalities in laboratory and stool investigations.

Aims

The current study aimed to evaluate whether patient access to the HR-IBD clinic in the Calgary region was within recommended wait times.

Methods

We conducted a cross-sectional study of charts from consented patients pulled from the EMR of five Gastroenterologists in the Calgary region that received HR-IBD referrals from Feb 2014 to Jan 2018. Of the 206 patients included, the majority were female (139 vs 65) and the mean age was 34.4 y, with no statistical difference in age between genders (p=0.81). Data analysis was done with Stata (StataCorp 2019).

Results

The mean time to initial consult was 74.8 days (median 64), whereas time to endoscopy was 85.5 days (median 77). There was no statistical difference in the mean wait times between genders. Of the patient charts reviewed, 27% of referrals had a confirmed diagnosis of IBD (CD 17%, UC 11%). Patients with a diagnosis of UC waited a mean of 60.1 days (median 60) until initial consultation and patients with a diagnosis of CD waited 77 days (median 63.5), although this was not statistically different (p=0.27). The mean time to endoscopy for patients with UC was 77 days (median 67), and 85.4 days for patients with CD (median 78.5), again not statistically different. These wait times are below the reported wait times for all GI complaints, of 92 days from referral to consultation and 155 days from referral to procedure, as reported in the SAGE survey (2012). Although there were no differences in time to consult and endoscopy between groups, there were notable differences in alarm symptoms reported in the referral. For example, rectal bleeding was reported in 81.8% of referrals that culminated in a diagnosis of UC, as compared to 50% in CD and 47.6% of non-IBD patients. Further analysis in which alarm symptoms correlate with a final diagnosis of IBD may guide triaging of referrals to decrease the time to diagnosis.

Conclusions

Timely access for consultation and endoscopy for patients presenting with high-risk features for IBD by Gastroenterology in the Calgary region remains above the CAG recommended wait times. Further correlation of high-risk features with a final diagnosis of IBD will help risk-stratify referrals in order to decrease time to IBD diagnosis.

Funding Agencies

CIHRAlberta Innovates Health Solutions

Genome-wide association study identified candidate genes controlling continuous storage root formation and bulking in hexaploid sweetpotato

BACKGROUND

Continuous storage root formation and bulking (CSRFAB) in sweetpotato is an important trait from agronomic and biological perspectives. Information about the molecular mechanisms underlying CSRFAB traits is lacking.

RESULTS

Here, as a first step toward understanding the genetic basis of CSRFAB in sweetpotato, we performed a genome-wide association study (GWAS) using phenotypic data from four distinct developmental stages and 33,068 single nucleotide polymorphism (SNP) and insertion-deletion (indel) markers. Based on Bonferroni threshold (p-value < 5 × 10- 7), we identified 34 unique SNPs that were significantly associated with the complex trait of CSRFAB at 150 days after planting (DAP) and seven unique SNPs associated with discontinuous storage root formation and bulking (DCSRFAB) at 90 DAP. Importantly, most of the loci associated with these identified SNPs were located within genomic regions (using Ipomoea trifida reference genome) previously reported for quantitative trait loci (QTL) controlling similar traits. Based on these trait-associated SNPs, 12 and seven candidate genes were respectively annotated for CSRFAB and DCSRFAB traits. Congruent with the contrasting and inverse relationship between discontinuous and continuous storage root formation and bulking, a DCSRFAB-associated candidate gene regulates redox signaling, involved in auxin-mediated lateral root formation, while CSRFAB is enriched for genes controlling growth and senescence.

CONCLUSION

Candidate genes identified in this study have potential roles in cell wall remodeling, plant growth, senescence, stress, root development and redox signaling. These findings provide valuable insights into understanding the functional networks to develop strategies for sweetpotato yield improvement. The markers as well as candidate genes identified in this pioneering research for CSRFAB provide important genomic resources for sweetpotato and other root crops.

A role for interleukin 17A in IBD-related neuroplasticity

BACKGROUND

Changes to the structure and function of the innervation of the gut contribute to symptom generation in inflammatory bowel diseases (IBD). However, delineation of the mechanisms of these effects has proven difficult. Previous work on sympathetic neurons identified interleukin (IL)-17A as a novel neurotrophic cytokine. Since IL-17A is involved in IBD pathogenesis, we tested the hypothesis that IL-17A contributes to neuroanatomical remodeling during IBD.

METHODS

Immunohistochemistry for tyrosine hydroxylase was used to identify sympathetic axons in mice with dextran sulphate sodium (DSS)-induced colitis and controls. Axon outgrowth from sympathetic neurons in response to incubation in cytokines or endoscopic patient biopsy supernatants was quantified.

KEY RESULTS

DSS-induced colitis led to an increase in tyrosine hydroxylase immunoreactivity in the inflamed colon but not the spleen. Colonic supernatants from mice with colitis and biopsy supernatants from Crohn's disease patients increased axon outgrowth from mouse sympathetic neurons compared to supernatants from uninflamed controls. An antibody that neutralized IL-17A blocked the ability of DSS-induced colitis and Crohn's disease supernatants to induce axon extension.

CONCLUSIONS AND INFERENCES

These findings identify IL-17A as a potential mediator of neuroanatomical remodeling of the gut innervation during IBD.

Demonstration of elevated levels of active cathepsin S in dextran sulfate sodium colitis using a new activatable probe

BACKGROUND

Proteases play a major role in inflammatory diseases of the gastrointestinal tract. Activatable probes are a major technological advance, enabling sensitive detection of active proteases in tissue samples. Our aim was to synthesize an activatable probe for cathepsin S and validate its use in a mouse model of colitis.

METHODS

We designed and synthesized a new fluorescent activatable probe, NB200, for the detection of active cathepsin S. Colitis was induced in C57BL/6 mice by the administration of 3% dextran sulfate sodium (DSS). Homogenized mouse colons, with or without the addition of the specific cathepsin S inhibitor MV026031, were incubated with NB200 in a fluorescent plate reader.

KEY RESULTS

NB200 selectively detected purified cathepsin S and not other common inflammatory proteases. Homogenates of colon from mice with DSS colitis induced a significant fluorescent increase when compared to control animals (control vs DSS: p < 0.05 at 200 min and p < 0.01 at 220-240 min), indicating cathepsin S activation. The cathepsin S inhibitor abolished this increase in fluorescence (DSS vs DSS + MV026031: p < 0.05 at 140 min, p < 0.01 at 180 min, p < 0.001 at 200-240 min), which confirms cathepsin S activation. Cathepsin S activity correlated with the disease activity index (Spearman r = 0.77, p = 0.017).

CONCLUSIONS & INFERENCES

Our investigation has demonstrated the utility of activatable probes for detecting protease activity in intestinal inflammation. Panels of such probes may allow 'signature' protease profiles to be established for a range of inflammatory diseases and disorders.

Inhibiting endocannabinoid biosynthesis: a novel approach to the treatment of constipation

BACKGROUND AND PURPOSE

Endocannabinoids are a family of lipid mediators involved in the regulation of gastrointestinal (GI) motility. The expression, localization and function of their biosynthetic enzymes in the GI tract are not well understood. Here, we examined the expression, localization and function of the enzyme diacylglycerol lipase-α (DAGLα), which is involved in biosynthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG).

EXPERIMENTAL APPROACH

Cannabinoid CB1 receptor-deficient, wild-type control and C3H/HeJ mice, a genetically constipated strain, were used. The distribution of DAGLα in the enteric nervous system was examined by immunohistochemistry. Effects of the DAGL inhibitors, orlistat and OMDM-188 on pharmacologically induced GI hypomotility were assessed by measuring intestinal contractility in vitro and whole gut transit or faecal output in vivo. Endocannabinoid levels were measured by mass spectrometry.

KEY RESULTS

DAGLα was expressed throughout the GI tract. In the intestine, unlike DAGLβ, DAGLα immunoreactivity was prominently expressed in the enteric nervous system. In the myenteric plexus, it was colocalized with the vesicular acetylcholine transporter in cholinergic nerves. In normal mice, inhibiting DAGL reversed both pharmacologically reduced intestinal contractility and pharmacologically prolonged whole gut transit. Moreover, inhibiting DAGL normalized faecal output in constipated C3H/HeJ mice. In colons incubated with scopolamine, 2-AG was elevated while inhibiting DAGL normalized 2-AG levels.

CONCLUSIONS AND IMPLICATIONS

DAGLα was expressed in the enteric nervous system of mice and its inhibition reversed slowed GI motility, intestinal contractility and constipation through 2-AG and CB1 receptor-mediated mechanisms. Our data suggest that DAGLα inhibitors may be promising candidates for the treatment of constipation.

Toward modulation of the endocannabinoid system for treatment of gastrointestinal disease: FAAHster but not "higher"

Cannabis has been used to treat various afflictions throughout the centuries, including nausea, vomiting, and pain. It has also been used recreationally for its psychotropic properties, which can include a pleasurable 'high' feeling and a decrease in anxiety and tension; however, other may experience dysphoria. Changes in cognition and psychomotor performance are also well-known with cannabis use. In recent years, our understanding of the endocannabinoid system (ECS) has progressed dramatically; the objective of identifying agents which may allow modulation of the ECS without significant psychotropic side effects may be possible. Inhibition of fatty acid amide hydrolase (FAAH), an important enzyme for the degradation of anandamide and other endogenous cannabinoids, is a promising target to achieve this goal. In this issue of Neurogastroenterology and Motility, Fichna and colleagues report on a novel selective FAAH inhibitor, PF-3845, with potent antinociceptive and antidiarrheal effects in a mouse model. In this context, we briefly review the components of the ECS, discuss pharmacologic targets for indirect cannabinoid receptor stimulation, and describe recent research with cannabinoids for gut disorders.

Using human intestinal biopsies to study the pathogenesis of irritable bowel syndrome

BACKGROUND

Although animal models of the irritable bowel syndrome (IBS) have provided important insights, there are no models that fully express the features of this complex condition. One alternative approach is the use of human intestinal biopsies obtained during endoscopic procedures to examine peripheral mechanisms in this disorder. These studies have served to confirm the existence of peripheral pathways in humans with IBS and have provided many new mechanistic insights. Two general approaches have been employed; one approach has been to examine the biological activity of mediators within the mucosal tissue of IBS patients and the other has been to examine changes in the structural properties of key signaling pathways contained within the biopsies. Using these approaches, important changes have been discovered involving the enteric nervous system and the extrinsic sensory pathway (dorsal root ganglia neurons), the immune system, and epithelial signaling in IBS patients compared to healthy subjects.

PURPOSE

This review will systematically explore these mechanistic pathways, highlight the implications of these novel findings and discuss some of the important limitations of this approach.

Enteric glia

The enteric nervous system is composed of both enteric neurones and enteric glia. Enteric glial cells were first described by Dogiel and are now known to outnumber neurones approximately 4 : 1. In the past, these cells were assumed to subserve a largely supportive role; however, recent evidence indicates that enteric glial cells may play a more active role in the control of gut function. In transgenic mouse models, where enteric glial cells are selectively ablated, the loss of glia results in intestinal inflammation and disruption of the epithelial barrier. Enteric glia are activated specifically by inflammatory insults and may contribute actively to inflammatory pathology via antigen presentation and cytokine synthesis. Enteric glia also express receptors for neurotransmitters and so may serve as intermediaries in enteric neurotransmission. Thus, enteric glia may serve as a link between the nervous and immune systems of the gut and may also have an important role in maintaining the integrity of the mucosal barrier and in other aspects of intestinal homeostasis.