Basic and clinical aspects of gastrointestinal pain. Pain. 2009;141:191-209. [PMID: 19155134 DOI: 10.1016/j.pain.2008.12.011]

Chronic Visceral Pain: New Peripheral Mechanistic Insights and Resulting Treatments

Chronic visceral pain is one of the most common reasons for patients with gastrointestinal disorders, such as inflammatory bowel disease or disorders of brain-gut interaction, to seek medical attention. It represents a substantial burden to patients and is associated with anxiety, depression, reductions in quality of life, and impaired social functioning, as well as increased direct and indirect health care costs to society. Unfortunately, the diagnosis and treatment of chronic visceral pain is difficult, in part because our understanding of the underlying pathophysiologic basis is incomplete. In this review, we highlight recent advances in peripheral pain signaling and specific physiologic and pathophysiologic preclinical mechanisms that result in the sensitization of peripheral pain pathways. We focus on preclinical mechanisms that have been translated into treatment approaches and summarize the current evidence base for directing treatment toward these mechanisms of chronic visceral pain derived from clinical trials. The effective management of chronic visceral pain remains of critical importance for the quality of life of suffers. A deeper understanding of peripheral pain mechanisms is necessary and may provide the basis for novel therapeutic interventions.

Asociación Española de Neurogastroenterología y Motilidad (ASENEM) updated review on the management of functional abdominal pain

Functional abdominal pain is a disorder in which central and peripheral sensitization processes converge, leading to hypersensitivity and allodynia. Differential diagnosis is made with organic digestive, renal, gynecological, endocrine, or neurological diseases. Treatment should be individualized for each patient. In cases of debilitating pain, therapy combining drugs with different mechanisms of action can be initiated, while in less severe cases, therapy with a progressive introduction of drugs based on clinical response is advised. The first line includes general lifestyle advice and antispasmodic substances, like peppermint oil, anticholinergic/antimuscarinic, and calcium channels antagonists. In the second line of treatment, neuromodulating agents are added. Finally, when these measures fail, third-line treatments such as gabapentine and atypical antipsychotics are considered. Psychological interventions should be considered if specialized therapists are available to manage these disorders.

Transcutaneous auricular vagus nerve stimulation in the treatment of disorders of consciousness: mechanisms and applications

This review provides an in-depth exploration of the mechanisms and applications of transcutaneous auricular vagus nerve stimulation (taVNS) in treating disorders of consciousness (DOC). Beginning with an exploration of the vagus nerve's role in modulating brain function and consciousness, we then delve into the neuroprotective potential of taVNS demonstrated in animal models. The subsequent sections assess the therapeutic impact of taVNS on human DOC, discussing the safety, tolerability, and various factors influencing the treatment response. Finally, the review identifies the current challenges in taVNS research and outlines future directions, emphasizing the need for large-scale trials, optimization of treatment parameters, and comprehensive investigation of taVNS's long-term effects and underlying mechanisms. This comprehensive overview positions taVNS as a promising and safe modality for DOC treatment, with a focus on understanding its intricate neurophysiological influence and optimizing its application in clinical settings.

Genetic and Pharmacological Blockade of Sigma-1 Receptors Attenuates Inflammation-Associated Hypersensitivity during Acute Colitis in CD1 Mice

Sigma-1 receptors (σ1Rs) are implicated in nociception, including pain sensitization, and inflammation. We assessed the role of σ1Rs on acute colitis-associated hypersensitivity using both genetic (constitutive knockout) and pharmacological blockade of the receptor. Colitis was induced in CD1 wild-type (WT) and σ1R KO mice (exposure to dextran sodium sulfate, 3%). A von Frey test was used to assess referred mechanosensitivity (abdominal and plantar withdrawal responses). The effects of the selective σ1R antagonists BD1063 and E-52862 were also assessed in WT animals. The expression of immune and sensory-related markers (RT-qPCR, Western blot) was assessed in the colon and lumbosacral spinal cord. The genetic ablation or pharmacological blockade of σ1Rs attenuated acute colonic inflammation in a similar manner. Mechanosensitivity was similar in WT and σ1R KO mice before colitis. In WT mice, but not in σ1R KO, colitis was associated with the development of referred mechanical hypersensitivity, manifested as a reduction in the withdrawal thresholds to mechanical probing (paw and abdominal wall). In WT mice, BD1063 and E-52862 blocked colitis-associated hypersensitivity. A genotype- and treatment-related differential regulation of sensory-related markers was detected locally (colon) and within the spinal cord. σ1Rs are involved in the development of acute intestinal inflammation and its associated referred mechanical hypersensitivity. The selective modulation of sensory-related pathways within the colon and spinal cord might be part of the underlying mechanisms. These observations support the pharmacological use of σ1R antagonists for the treatment of intestinal inflammation-induced hypersensitivity.

Mendelian randomization study of gastroesophageal reflux disease and major depression

This study systematically investigated the causal relationship between gastroesophageal reflux disease (GERD) and major depression (MD). Single-nucleotide polymorphisms (SNPs) associated with disorders of interest were screened via the genome-wide association study (GWAS) enrolling individuals of European descent. Summary-level data for GERD and MD were extracted from the UK Biobank. The inverse-variance-weighted (IVW) method was utilized as the primary analysis. Sensitivity analyses were performed using the MR-Egger method, the Maximum likelihood method, the MR-pleiotropy residual sum outlier (MR-PRESSO) method, and MR-robust adjusted profile score (MR-RAPS) method. MR-Egger regression, heterogeneity tests, pleiotropy tests, and leave-one-out tests were also performed to analyze sensitivity. The MR Steiger test was used to verify the directionality of the exposure to the outcome. An available website tool (https://shiny.cnsgenomics.com/mRnd/) was used to calculate the statistical power of MR analysis. Meta-analysis was applied to test MD's average genetically predicted effect on GERD. Our MR study showed a bidirectional causal association between MD and GERD. Regarding MD to GERD, there was a positive association between them; the ORs were 1.500 (95% CI = 1.320-1.704; P = 4.91E-10) and 2.058 (95% CI = 1.868-2.267; P = 2.20E-48) in the IVW method, respectively. In addition, the meta-analysis also showed a strong positive causal association between MD and GERD. When exposure and outcome were reversed, genetic predisposition to GERD was significantly associated with the overall Risk of advanced MD (ieu-a-1187, OR = 1.982, 95% CI = 1.694-2.319, P = 1.41E-17; ieu-b-102, OR = 1.612, 95% CI = 1.530-2.700, P = 1.15E-70). Our study provides 100% power to detect the causal effect of MD on GERD and vice versa. Genetically predicted MD was positively associated with higher GERD risk, and vice versa. Our study reminds clinicians to pay attention to screening for GERD when diagnosing and treating MD and vice versa. Moreover, there may be positive feedback between MD and GERD when treating and preventing one disorder may benefit the treatment and prevention of the other.

Tramadol for chronic pain in adults: protocol for a systematic review with meta-analysis and trial sequential analysis of randomised clinical trials

BACKGROUND

Chronic pain in adults is a frequent clinical symptom with a significant impact on patient well-being. Therefore, sufficient pain management is of utmost importance. While tramadol is a commonly used pain medication, the quality of evidence supporting its use has been questioned considering the observed adverse events. Our objective will be to assess the benefits and harms of tramadol compared with placebo or no intervention for chronic pain.

METHODS/DESIGN

We will conduct a systematic review of randomised clinical trials with meta-analysis and trial sequential analysis to assess the beneficial and harmful effects of tramadol in any dose, formulation, or duration. We will accept placebo or no intervention as control interventions. We will include adult participants with any type of chronic pain, including cancer-related pain. We will systematically search the Cochrane Library, MEDLINE, EMBASE, Science Citation Index, and BIOSIS for relevant literature. We will follow the recommendations by Cochrane and the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The risk of systematic errors ('bias') and random errors ('play of chance') will be assessed. The certainty of evidence will be evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

DISCUSSION

Although tramadol is often being used to manage chronic pain conditions, the beneficial and harmful effects of this intervention are unknown. The present review will systematically assess the current evidence on the benefits and harms of tramadol versus placebo or no intervention to inform clinical practice and future research.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019140334.

Factors influencing rectal hypersensitivity in irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND

A frequent, although not universal, feature of irritable bowel syndrome (IBS) is heightened sensitivity to mechanical stimulation of the rectum, termed rectal hypersensitivity (RH). Differences in RH-based on sex, IBS subtype, IBS diagnostic criteria and age of population studied are incompletely understood. We aimed to determine whether IBS population had lower pain thresholds than healthy controls.

METHODS

We searched MEDLINE and EMBASE databases (1970-2021). Prospective studies that compared pain/discomfort thresholds to mechanical rectal stimuli in IBS and healthy controls were included. Data were pooled for meta-analyses and effect sizes were calculated with 95% confidence interval (CIs).

RESULTS

Our search strategy identified 809 studies of which 32 studies met the inclusion criteria. Reduced rectal pain thresholds was more common in IBS patients compared to healthy controls with an effect size of 1.00 95% CIs (0.77-1.24) (p < 0.0001) (I²  = 78.6%). The pediatric IBS population had lower pain thresholds than adult IBS populations (p = 0.05) but no difference based on IBS diagnostic criteria, subtype or sex.

CONCLUSION & INFERENCES

The results suggest that reduced rectal pain threshold to experimental stimulation is far more common in IBS patients than healthy controls. Further research is required to understand the pathophysiological and therapeutic implications of rectal sensitivity such as its role in measuring response to treatment and prognosis in IBS.

Multi-omics for biomarker approaches in the diagnostic evaluation and management of abdominal pain and irritable bowel syndrome: what lies ahead

Reliable biomarkers for common disorders of gut-brain interaction characterized by abdominal pain, including irritable bowel syndrome (IBS), are critically needed to enhance care and develop individualized therapies. The dynamic and heterogeneous nature of the pathophysiological mechanisms that underlie visceral hypersensitivity have challenged successful biomarker development. Consequently, effective therapies for pain in IBS are lacking. However, recent advances in modern omics technologies offer new opportunities to acquire deep biological insights into mechanisms of pain and nociception. Newer methods for large-scale data integration of complementary omics approaches have further expanded our ability to build a holistic understanding of complex biological networks and their co-contributions to abdominal pain. Here, we review the mechanisms of visceral hypersensitivity, focusing on IBS. We discuss candidate biomarkers for pain in IBS identified through single omics studies and summarize emerging multi-omics approaches for developing novel biomarkers that may transform clinical care for patients with IBS and abdominal pain.

Inappropriate manipulation and drainage exacerbate post-operative pain and prolong the hospital stay after laparoscopic appendectomy for pediatric complicated appendicitis

Background

This study examined whether drain placement or not is associated with the postoperative outcomes of pediatric patients following trans-umbilical single-port laparoscopic appendectomy (TUSPLA) for complicated appendicitis.

Methods

The medical records of pediatric patients undergoing TUSPLA for acute complicated appendicitis from January 2012 to September 2018 in Kaohsiung Chang Gung Memorial Hospital were reviewed retrospectively. They were classified according to whether they received passive drainage with a Penrose drain (Penrose group) (19), active drainage with a Jackson-Pratt drain with a vacuum bulb (JP group) (16), or no drain (non-drain group) (86). The postoperative outcomes of the three groups were compared.

Results

Postoperative visual analog scale pain score was significantly higher in the non-drain group than in either the JP group or Penrose group. Patients in the Penrose group had a significantly longer postoperative hospital stay than those in the non-drain group and a higher rate of intra-abdominal abscess, while patients in the JP group had a significantly shorter postoperative hospital stay; moreover, no patient in JP group developed a postoperative intra-abdominal abscess.

Conclusions

Compared to passive drainage with a Penrose drain or no drain, active drainage with a JP drain shorter the postoperative hospital stay and decreased the risk of postoperative intra-abdominal abscess.

Association of opioid fills with centers for disease control and prevention opioid guidelines and payer coverage policies: physician, insurance and geographic factors

Background The Centers for Disease Control and Prevention (CDC) issued guidelines and certain healthcare payers have made pharmacy coverage changes (PCC) focusing on regulating prescription opioids. Aim We evaluated differences in the rate of first-time opioid fills at doses ≥ 50 morphine milligram equivalents (MME)/day and first-time opioid fills with benzodiazepine fill overlap following the CDC guidelines and following a PCC between provider types, geographic locations, and insurance types. Method We used OptumLabs® Data Warehouse claims data between 2014 and 2018. Subjects were opioid naïve non-cancer care patients, 18 years and older who had an identified chronic pain condition ICD diagnosis within 2 weeks prior to their first-time opioid fill. We used multiple treatment period segmented regression analysis with interaction terms to test the differences between primary care providers (PCPs) and specialist providers (SPs), urban and rural primary care service areas (PCSAs), and Medicare Advantage (MA) and commercially insured patients (CIPs) in their first-time opioid fill patterns. Results Prescribing first-time opioid fills at doses ≥ 50MME/day declined following the CDC guidelines and PCC, the decline was greater among SPs than PCPs and in rural PCSAs than urban PCSAs. Also, following the CDC guidelines, the decline was greater among MA patients however following the PCC the decline was greater among CIPs. There were no differences in rate of first-time opioid fill with benzodiazepine overlap between groups. Conclusion Responses to the CDC opioid guidelines and a PCC differed between PCPs and SPs, urban and rural PCSAs, and when prescribing to MA and CIPs. Understanding these differences is important to help inform future guidelines.

Intestinal inflammation-associated hypersensitivity is attenuated in a DSS model of colitis in Sigma-1 knockout C57BL/6 mice

Sigma-1 receptors (σ1R) have been implicated in several pain pathways. We assessed the implication of σ1Rs in the development of intestinal inflammation and inflammation-associated referred hypersensitivity in a model of colitis in σ1R knockout (KO) mice. Colitis was induced with dextran sulfate sodium (DSS) in wild type (WT) and σ1R KO mice. The development of referred mechanical hypersensitivity (von Frey test) was assessed. Colonic and spinal changes in expression of immune- and sensory-related markers were also investigated (RT-qPCR/Western blot). Absence of σ1Rs had little impact in colitis generation and progression, although during the chronic phase a reduction in edema and a down-regulation of iNOS gene expression was observed. In σ1R KO mice, inflammation-associated hypersensitivity was significantly attenuated (paw) or completely prevented (abdomen). During colitis, in WT mice, changes in the colonic expression of nociceptive markers were observed during the acute and chronic phases of inflammation. Although σ1R KO mice showed similar regulation in the acute phase, an attenuated response was observed during the chronic phase of colitis. These differences were especially relevant for CB2 and TRPV1 receptors, which could play an important role in σ1-mediated regulation of sensitivity. No changes were detected on ERK phosphorylation at the level of the lumbosacral spinal cord. In summary, intestinal inflammation-associated referred hyperalgesia was reduced (paw) or absent (abdomen) in σ1R KO mice, thus confirming an important role for σ1R in the development of colitis-associated hypersensitivity. These results identify σ1Rs as a possible therapeutic target for the treatment of hypersensitivity associated to intestinal inflammation.

Association of 3 CDC opioid prescription guidelines for chronic pain and 2 payer pharmacy coverage changes on opioid initiation practices

BACKGROUND: Due to the US opioid epidemic, in March of 2016, the Centers for Disease Control and Prevention (CDC) published new guidelines for primary care providers on opioid prescribing for chronic pain. Payer coverage changes were also implemented to help modify opioid prescribing behavior. Whether these initiatives were associated with changes in opioid initiation patterns is unknown. OBJECTIVE: To assess the association between 3 of the 2016 CDC guidelines and 2 subsequent payer pharmacy coverage changes with changes in opioid initiation behavior across different provider specialties. METHODS: We conducted a real-world evidence study using claims data from OptumLabs Data Warehouse between January of 2014 and December of 2018. Subjects were continuously enrolled opioid naive patients, aged at least 18 years, who had at least 1 chronic pain diagnosis within 2 weeks before their first (first-time) opioid prescription. The study used multiple treatment period segmented regression analysis to evaluate the association, across different provider specialties, between the CDC guideline release and the payer pharmacy coverage changes with immediate change in level and overall change in the rate of first-time extended-release opioid prescriptions, firsttime opioid prescriptions at doses of at least 50 MME (morphine milligram equivalent) per day, and first-time opioid prescriptions with overlapping benzodiazepine prescription. RESULTS: The CDC guidelines were not associated with any change in the rate of first-time prescriptions of extended-release opioids. However, a January 2017 payer pharmacy coverage change was associated with a reduction over time in first-time extended-release opioid prescription rates by 22.15 in every 100,000 prescriptions (CI = -40.04 to -2.92, P = 0.013). The CDC guidelines were associated with an immediate decline in level of first-time opioid prescription at doses of at least 50 MME per day by 74.00 in every 10,000 prescriptions (CI = -124.86 to -23.13, P = 0.004) and an increased rate of decline over time by 13.64 in every 10,000 prescriptions (CI = -17.07 to -10.21, P < 0.001). These associations varied across provider types and specialties. The March 2018, payer coverage change was associated with an immediate reduction in level of first-time opioid prescriptions at doses of at least 50 MME per day across all specialties and an increased reduction over time among surgeons. The CDC guidelines were associated, respectively, with a reduction in the rate of overlapping first-time opioid prescriptions with benzodiazepines among family medicine, internal medicine, surgeons, emergency medicine providers, and providers with unknown specialty by 6.11, 5.10, 2.89, 11.43, and 9.11 in every 10,000 prescriptions monthly (CI = -9.48 to -2.73, -9.86 to -0.35, -5.40 to -0.38, -17.26 to -5.61 and -11.96 to -6.25, respectively, P < 0.001, P = 0.035, P = 0.024, P < 0.001 and P < 0.001). CONCLUSIONS: Some specialist providers also adopted the CDC guidelines, and the response to the guidelines differed across various provider specialties. Some CDC guidelines were associated with a reduction in high-risk first-time opioid prescriptions. Payer pharmacy coverage changes reinforced the guidelines both in situations where the CDC guidelines did and did not show any association. DISCLOSURE: This research was funded by Agency for Healthcare Research and Quality (R01 HS025164; PI: Karaca-Mandic). Karaca-Mandic reports grants from the American Cancer Society and Sempre Health, along with fees from Tactile Medical and Precision Health Economics, unrelated to this study. The other authors have nothing to disclose.

Post-inflammatory Abdominal Pain in Patients with Inflammatory Bowel Disease During Remission: A Comprehensive Review

Patients with inflammatory bowel disease often experience ongoing pain even after achieving mucosal healing (i.e., post-inflammatory pain). Factors related to the brain-gut axis, such as peripheral and central sensitization, altered sympatho-vagal balance, hypothalamic-pituitary-adrenal axis activation, and psychosocial factors, play a significant role in the development of post-inflammatory pain. A comprehensive study investigating the interaction between multiple predisposing factors, including clinical psycho-physiological phenotypes, molecular mechanisms, and multi-omics data, is still needed to fully understand the complex mechanism of post-inflammatory pain. Furthermore, current treatment options are limited and new treatments consistent with the underlying pathophysiology are needed to improve clinical outcomes.

The α isoform of cGMP-dependent protein kinase 1 (PKG1α) is expressed and functionally important in intrinsic primary afferent neurons of the guinea pig enteric nervous system

BACKGROUND

Intrinsic primary afferent neurons (IPANs) enable the gut to manifest reflexes in the absence of CNS input. PKG1α is selectively expressed in a subset of neurons in dorsal root ganglia (DRG) and has been linked to nociception and long-term hyperexcitability.

METHODS

We used immunoblotting, immunocytochemistry, and in vitro assays of IPAN-dependent enteric functions to test hypotheses that subsets of primary neurons of the ENS and DRG share a reliance on PKG1α expression.

KEY RESULTS

PKG1α immunoreactivity was demonstrated in immunoblots from isolated myenteric ganglia. PKG1α, but not PKG1β, immunoreactivity, was coincident with that of neuronal markers (HuC/D; β3-tubulin) in both enteric plexuses. PKG1α immunoreactivity also co-localized with the immunoreactivities of the IPAN markers, calbindin (100%; myenteric plexus) and cytoplasmic NeuN (98 ± 1% submucosal plexus). CGRP-immunoreactive DRG neurons, identified as visceral afferents by retrograde transport, were PKG1α-immunoreactive. We used intraluminal cholera toxin to determine whether PKG1α was necessary to enable stimulation of the mucosa to activate Fos in enteric neurons. Tetrodotoxin (1.0 µM), low Ca²⁺ /high Mg²⁺ media, and the PKG inhibitor, N46 (100 µM), all inhibited Fos activation in myenteric neurons. N46 also concentration dependently inhibited peristaltic reflexes in isolated preparations of distal colon (IC₅₀  = 83.3 ± 1.3 µM).

CONCLUSIONS & INFERENCES

These data suggest that PKG1α is present and functionally important in IPANs and visceral afferent nociceptive neurons.

Gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GERD) is a common disorder in adults and children. The global prevalence of GERD is high and increasing. Non-erosive reflux disease is the most common phenotype of GERD. Heartburn and regurgitation are considered classic symptoms but GERD may present with various atypical and extra-oesophageal manifestations. The pathophysiology of GERD is multifactorial and different mechanisms may result in GERD symptoms, including gastric composition and motility, anti-reflux barrier, refluxate characteristics, clearance mechanisms, mucosal integrity and symptom perception. In clinical practice, the diagnosis of GERD is commonly established on the basis of response to anti-reflux treatment; however, a more accurate diagnosis requires testing that includes upper gastrointestinal tract endoscopy and reflux monitoring. New techniques and new reflux testing parameters help to better phenotype the condition. In children, the diagnosis of GERD is primarily based on history and physical examination and treatment vary with age. Treatment in adults includes a combination of lifestyle modifications with pharmacological, endoscopic or surgical intervention. In refractory GERD, optimization of proton-pump inhibitor treatment should be attempted before a series of diagnostic tests to assess the patient's phenotype.

Neuro-Immune Modulation Effects of Sacral Nerve Stimulation for Visceral Hypersensitivity in Rats

Background: Visceral hypersensitivity (VH) is one of the underlying pathophysiologies of irritable bowel syndrome. Mast cell overactivation has been found to be one of the main causes of VH. We investigated the effects and mechanisms of actions of sacral nerve stimulation (SNS) on visceral pain in a rodent model of VH.

Methods: The VH was established by an intrarectal infusion of AA in 10-day-old pups. Rats were chronically implanted with electrodes for SNS and recording electromyogram (EMG) and electrocardiogram. The acute study was performed in 2-randomized sessions with SNS (14 Hz, 330 μs, 40% motor threshold or MT, 30 min) or sham-SNS. Later on, rats were randomized into SNS/sham-SNS groups and a chronic study was performed with 2 h-daily SNS or sham-SNS for 21 days. Visceromotor reflexes were assessed by abdominal EMG and withdrawal reflex (AWR). Colon tissues were collected to study colonic acetylcholine (ACh), the enteric neurons (ChAT, nNOS, and PGP9.5), mast cells activity [Tryptase, prostaglandins E2 (PGE2), and cyclooxygenases-2 (COX2)] and pain markers [nerve growth factor (NGF) and Sub-P].

Key Results: Sacral nerve stimulation significantly improved visceromotor reflexes assessed by the EMG and AWR, compared with sham-SNS. SNS normalized the protein expressions of ChAT and nNOS and regulated mast cells activity by downregulating Tryptase, COX2, and PGE2. Neonatal AA administration upregulated NGF and Sub-P; chronic SNS significantly decreased these pain biomarkers. Concurrently, chronic SNS increased ACh in colon tissues and vagal efferent activity.

Conclusions: Sacral nerve stimulation reduces VH in rats and this ameliorating effect might be attributed to the suppression of mast cell overactivation in the colon tissue via the modulation of autonomic nervous system functions.

Rectal Hypersensitivity in Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

Abdominal pain is a key symptom of inflammatory bowel disease (IBD), particularly in active IBD, but also occurs in patients with quiescent disease suggesting that mechanisms other than active inflammation may be responsible. Putative hypothesis to explain chronic abdominal pain in patients with quiescent IBD includes crossover with irritable bowel syndrome where rectal hypersensitivity is common and has pathophysiological implications. In contrast, in IBD, the role of rectal hypersensitivity has not been established. We aimed to determine if rectal hypersensitivity was more common in IBD compared to a healthy control population. We searched MEDLINE and EMBASE databases (1970-2018). Prospective studies that measured pain/discomfort thresholds to mechanical rectal stimuli in IBD and healthy controls were included. Data were pooled for meta-analysis and effect sizes were calculated with 95% confidence intervals (CIs). Our search strategy identified 222 citations of which 8 met the inclusion criteria, covering 133 individuals with IBD (67 men), aged between 10 and 77 compared to 99 healthy controls (55 men), aged between 10 and 67. The prevalence of rectal hypersensitivity in IBD compared to healthy controls was similar with an effect size of 0.59 (95% CIs: -0.27 to 1.44, P = .16, I ² = 87.3%). Subgroup analysis did show a significant effect size for patients compared to healthy controls with active disease (1.32) but not for quiescent disease (-0.02). These results suggest that reduced rectal pain thresholds to experimental stimulation are not seen in IBD populations except during active flares of the disease. Further research is required to understand the pathophysiology of chronic abdominal pain in quiescent IBD populations with and without chronic abdominal pain to identify appropriate management strategies.

Transcranial Auricular Vagus Nerve Stimulation (taVNS) and Ear-EEG: Potential for Closed-Loop Portable Non-invasive Brain Stimulation

No matter how hard we concentrate, our attention fluctuates – a fact that greatly affects our success in completing a current task. Here, we review work from two methods that, in a closed-loop manner, have the potential to ameliorate these fluctuations. Ear-EEG can measure electric brain activity from areas in or around the ear, using small and thus portable hardware. It has been shown to capture the state of attention with high temporal resolution. Transcutaneous auricular vagus nerve stimulation (taVNS) comes with the same advantages (small and light) and critically current research suggests that it is possible to influence ongoing brain activity that has been linked to attention. Following the review of current work on ear-EEG and taVNS we suggest that a combination of the two methods in a closed-loop system could serve as a potential application to modulate attention.

Transcutaneous vagus nerve stimulation in patients with attention-deficit/hyperactivity disorder: A viable option?

Individuals with attention-deficit/hyperactivity disorder (ADHD) suffer from a range of cognitive and behavioral problems that severely impair their educational and occupational attainment. ADHD symptoms have been linked to structural and functional changes within and between different brain regions, particularly the prefrontal cortex. At the system level, reduced availability of the neurotransmitters dopamine (DA) and norepinephrine (NE) but also γ-aminobutyric acid (GABA) have been repeatedly demonstrated. Recently, non-invasive brain stimulation (NIBS) techniques have been explored as treatment alternatives to alter dysfunctional activation patterns in specified brain areas or networks. In the current paper, we introduce transcutaneous vagus nerve stimulation (tVNS) as a systemic approach to directly affect NE and GABA neurotransmission. TVNS is a non-drug intervention with low risk and proven efficacy in improving cognitive particularly executive functions. It is easy to apply and therefore well-suited to provide home-based or mobile treatment options allowing a significant increase in treatment intensity and providing easier access to medical care for individuals who are unable to regularly visit a clinician. We describe in detail the underlying mechanisms of tVNS and current fields of application and discuss its potential as an adjuvant treatment for ADHD.

The role of serotonin in the control of esophageal sensitivity assessed by multimodal stimulation in health

BACKGROUND

Esophageal hypersensitivity is considered an important pathophysiological mechanism in refractory gastroesophageal reflux disease (GERD) patients. Serotonin (5-HT) plays an important role in the regulation of GI (gastrointestinal) secretion, motility and sensitivity. Previous studies found that altered 5-HT availability has no clear effects on esophageal/GI sensations. Our aim was therefore to investigate the role of 5-HT in esophageal sensitivity in healthy volunteers (HV).

METHODS

Esophageal sensitivity to thermal, mechanical, electrical, and chemical stimuli was assessed in 3 different placebo-controlled studies. In the first study, the effect of citalopram (40 mg; 5-HT reuptake inhibitor; intravenous) was investigated (n = 14). In the second study, the effect of buspirone (20 mg; 5HT1A agonist; oral) was investigated (n = 10). In the third study, acute tryptophan depletion (ATD) was used to decrease 5-HT levels to investigate the effect of reduced 5-HT availability on esophageal sensitivity (n = 15).

KEY RESULTS

No difference was observed in esophageal sensitivity after the administration of citalopram or buspirone (all p > 0.06). In contrast, pain perception threshold to chemical stimulation was increased after ATD (p = 0.017, Cohen's d+ = 0.67). No effect was found on the first perception or pain tolerance threshold. ATD had no influence on esophageal sensitivity to thermal, mechanical, and electrical stimulation compared with placebo.

CONCLUSIONS AND INFERENCES

ATD, which induces 5-HT depletion, significantly decreased pain perception threshold during chemical stimulation, without affecting sensitivity to mechanical, thermal, or electrical stimulation. These findings confirm the involvement of 5-HT in the control of esophageal acid sensitivity, but identifying the receptors involved requires more ligands and studies.

Upper Gastrointestinal Sensitization And Symptom Generation

Functional gastrointestinal disorders (FGIDs) are a highly prevalent group of heterogeneous disorders, and their diagnostic criteria are symptom-based, with the absence of anatomical and biochemical abnormalities of the gastrointestinal tract. Chronic visceral symptoms are common both in patients with an identifiable organic disease but also in FGID patients. Patients suffering from upper gastrointestinal functional disorders typically present with various symptoms such as early satiety, postprandial fullness, bloating, nausea, vomiting, and epigastric pain. Considering their increasing prevalence, difficulties in diagnosis, and low quality of life, FGIDs have become an emerging problem in gastroenterology. We aimed to provide an updated summary of pathways involved in visceral sensitization. We examined the recent literature searching for evidence of the most important studies about the mechanisms underlying gastrointestinal symptom generation and sensitization.

Critical evaluation of animal models of visceral pain for therapeutics development: A focus on irritable bowel syndrome

The classification of chronic visceral pain is complex, resulting from persistent inflammation, vascular (ischemic) mechanisms, cancer, obstruction or distension, traction or compression, and combined mechanisms, as well as unexplained functional mechanisms. Despite the prevalence, treatment options for chronic visceral pain are limited. Given this unmet clinical need, the development of novel analgesic agents, with defined targets derived from preclinical studies, is urgently needed. While various animal models have played an important role in our understanding of visceral pain, our knowledge is far from complete. Due to the complexity of visceral pain, this document will focus on chronic abdominal pain, which is the major complaint in patients with disorders of the gut-brain interaction, also referred to as functional gastrointestinal disorders, such as irritable bowel syndrome (IBS). Models for IBS are faced with challenges including a complex clinical phenotype, which is comorbid with other conditions including anxiety, depression, painful bladder syndrome, and chronic pelvic pain. Based upon the multifactorial nature of IBS with complicated interactions between biological, psychological, and sociological variables, no single experimental model recapitulates all the symptoms of IBS. This position paper will contextualize chronic visceral pain using the example of IBS and focus on its pathophysiology while providing a critical review of current animal models that are most relevant, robust, and reliable in which to screen promising therapeutics to alleviate visceral pain and delineate the gaps and challenges with these models. We will also highlight, prioritize, and come to a consensus on the models with the highest face/construct validity.

Gastrointestinal pain

Gastrointestinal (GI) pain - a form of visceral pain - is common in some disorders, such as irritable bowel syndrome, Crohn's disease and pancreatitis. However, identifying the cause of GI pain frequently represents a diagnostic challenge as the clinical presentation is often blurred by concomitant autonomic and somatic symptoms. In addition, GI pain can be nociceptive, neuropathic and associated with cancer, but in many cases multiple aetiologies coexist in an individual patient. Mechanisms of GI pain are complex and include both peripheral and central sensitization and the involvement of the autonomic nervous system, which has a role in generating the symptoms that frequently accompany pain. Treatment of GI pain depends on the precise type of pain and the primary disorder in the patient but can include, for example, pharmacological therapy, cognitive behavioural therapies, invasive surgical procedures, endoscopic procedures and lifestyle alterations. Owing to the major differences between organ involvement, disease mechanisms and individual factors, treatment always needs to be personalized and some data suggest that phenotyping and subsequent individual management of GI pain might be options in the future.

The anatomical basis for transcutaneous auricular vagus nerve stimulation

The array of end organ innervations of the vagus nerve, coupled with increased basic science evidence, has led to vagus nerve stimulation (VNS) being explored as a management option in a number of clinical disorders, such as heart failure, migraine and inflammatory bowel disease. Both invasive (surgically implanted) and non-invasive (transcutaneous) techniques of VNS exist. Transcutaneous VNS (tVNS) delivery systems rely on the cutaneous distribution of vagal afferents, either at the external ear (auricular branch of the vagus nerve) or at the neck (cervical branch of the vagus nerve), thus obviating the need for surgical implantation of a VNS delivery device and facilitating further investigations across a wide range of uses. The concept of electrically stimulating the auricular branch of the vagus nerve (ABVN), which provides somatosensory innervation to several aspects of the external ear, is relatively more recent compared with cervical VNS; thus, there is a relative paucity of literature surrounding its operation and functionality. Despite the increasing body of research exploring the therapeutic uses of auricular transcutaneous VNS (tVNS), a comprehensive review of the cutaneous, intracranial and central distribution of ABVN fibres has not been conducted to date. A review of the literature exploring the neuroanatomical basis of this neuromodulatory therapy is therefore timely. Our review article explores the neuroanatomy of the ABVN with reference to (1) clinical surveys examining Arnold's reflex, (2) cadaveric studies, (3) fMRI studies, (4) electrophysiological studies, (5) acupuncture studies, (6) retrograde tracing studies and (7) studies measuring changes in autonomic (cardiovascular) parameters in response to auricular tVNS. We also provide an overview of the fibre composition of the ABVN and the effects of auricular tVNS on the central nervous system. Cadaveric studies, of which a limited number exist in the literature, would be the 'gold-standard' approach to studying the cutaneous map of the ABVN; thus, there is a need for more such studies to be conducted. Functional magnetic resonance imaging (fMRI) represents a useful surrogate modality for discerning the auricular sites most likely innervated by the ABVN and the most promising locations for auricular tVNS. However, given the heterogeneity in the results of such investigations and the various limitations of using fMRI, the current literature lacks a clear consensus on the auricular sites that are most densely innervated by the ABVN and whether the brain regions secondarily activated by electrical auricular tVNS depend on specific parameters. At present, it is reasonable to surmise that the concha and inner tragus are suitable locations for vagal modulation. Given the therapeutic potential of auricular tVNS, there remains a need for the cutaneous map of the ABVN to be further refined and the effects of various stimulation parameters and stimulation sites to be determined.

Cannabinoids versus placebo or no intervention for pain: protocol for a systematic review with meta-analysis and trial sequential analysis

INTRODUCTION

Pain is a frequent clinical symptom with significant impact on the patient's well-being. Therefore, adequate pain management is of utmost importance. While cannabinoids have become a more popular alternative to traditional types of pain medication among patients, the quality of evidence supporting the use of cannabinoids has been questioned. The beneficial and harmful effects of cannabinoids in patients with pain is unknown. Accordingly, we aim to assess the efficacy, tolerability and safety of cannabinoids (herbal, plant-derived extracts and synthetic) compared with placebo or no intervention for any type of pain.

METHODS AND ANALYSES

We will conduct a systematic review of randomised clinical trials with meta-analysis and Trial Sequential Analysis to assess the beneficial and harmful effects of cannabinoids in any dose, formulation and duration. We will accept placebo or no treatment as control interventions. We will include participants with any type of pain (acute and chronic pain, cancer-related pain, headache, neuropathic pain or any other types of pain). We will systematically search The Cochrane Library, MEDLINE, Embase, Science Citation Index and BIOSIS for relevant literature. We will follow the recommendations by Cochrane and the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. The risk of systematic errors (bias) and random errors (play of chance) will be assessed. The overall certainty of evidence will be evaluated using the Grading of Recommendations Assessment, Development and Evaluation approach.

ETHICS AND DISSEMINATION

Ethical approval is not a requirement since no primary data will be collected. The findings of this systematic review will be submitted for peer-reviewed publication and disseminated in national and international conferences.

DISCUSSION

Although cannabinoids are now being used to manage different pain conditions, the evidence for the clinical effects are unclear. The present review will systematically assess the current evidence for the benefits and harms of cannabinoids to inform practice and future research.

Implications of the Opioid Epidemic for the Clinical Gastroenterology Practice

PURPOSE OF REVIEW

The opioid epidemic in the USA has led to a rise in opioid-related gastrointestinal (GI) side effects that are often difficult to diagnose and treat. The aim of this report is to discuss opioid pathophysiology, opioid-related GI side effects, clinical presentation, and diagnostic criteria and to review the current pharmacotherapy available.

RECENT FINDINGS

Opioid-related GI disorders are increasingly recognized and include, but are not limited to, opioid-induced esophageal dysfunction (OIED), gastroparesis, opioid-induced constipation (OIC), narcotic bowel syndrome (NBS), acute post-operative ileus, and anal sphincter dysfunction. Treatment of these conditions is challenging. OIC has the most available pharmacotherapy for treatment, including classical laxatives, peripherally acting μ-receptor antagonists (PAMORAs), novel therapies (lubiprostone, prucalopride- 5-HT agonist), and preventative therapies (PR oxycodone/naloxone). The gastrointestinal effects of opioid therapy are variable and often debilitating. While medical management for some opioid-related GI side effects exists, limiting or completely avoiding opioid use for chronic non-cancer pain will mitigate these effects most effectively.

An Approach to the Patient With Chronic Undiagnosed Abdominal Pain

Abdominal pain is a common reason for referral to a gastroenterologist. The workup of patients with chronic abdominal pain can be extremely challenging as clinicians are responsible for determining whether the patient can be observed or treated symptomatically or this abdominal pain heralds a more systemic disease. The differential is typically wide and given the innervation of the abdomen, localization of abdominal pain does not always provide clear insight into the etiology. This review attempts to help the gastroenterologist narrow down that broad differential and focus on key elements of the patient visit. We emphasize the importance of a detailed history from the patient, along with review-specific details of their history and physical examination that can clue one in about the etiology of the abdominal pain. We review the causes of diffuse abdominal pain that may not first be considered along with uncommon causes of localized abdominal pain. We also review the functional causes of abdominal pain and the importance of identifying these disorders, to avoid unnecessary testing that commonly occurs with these patients.

Ameliorating effects of optimized gastric electrical stimulation and mechanisms involving nerve growth factor and opioids in a rodent model of gastric hypersensitivity

BACKGROUND

Gastric electrical stimulation (GES) has been applied to treat gastric motility disorders for decades. This study was designed to investigate the effects and mechanisms of GES for visceral hypersensitivity in a rodent model of functional dyspepsia (FD).

METHODS

Male Sprague-Dawley rat pups at 10-days old received 0.1% iodoacetamide (IA) daily for 6 days. The experiments were performed when the rats reached 8-11 weeks of age, and visceral hypersensitivity was established. Then, GES parameters were optimized and the chronic effects of GES on gastric hypersensitivity were assessed by electromyogram (EMG). Naloxone (3 mg/kg), D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP, 1 mg/kg), and anti-NGF (16 μg/kg) were individually intraperitoneally injected to investigate opioid and nerve growth factor (NGF) mechanisms. Tissues were analyzed for NGF expression.

KEY RESULTS

In the IA-treated rats, the visceromotor response to gastric distension was significantly increased, and both acute GES with optimized stimulation parameters (0.25 seconds on, 0.25 seconds off, 100 Hz, 0.25 ms, 6 mA) and chronic GES (7 days, 2 hours/day) normalized gastric hypersensitivity. The inhibitory effect of GES on gastric hypersensitivity was blocked by naloxone and CTOP. Anti-NGF normalized EMG responses in IA-treated rats. The expressions of NGF in the tissues of IA-treated rats were dramatically increased, and these increases were suppressed with GES.

CONCLUSIONS AND INFERENCES

GES with optimized parameters improves gastric hypersensitivity induced by neonatal treatment of IA mediated peripherally by suppressing NGF and via the opioid mechanism involving the µ receptor. GES as a potential therapy for treating visceral pain may be explored in clinical studies.

Single-cell RNAseq reveals seven classes of colonic sensory neuron

OBJECTIVE

Integration of nutritional, microbial and inflammatory events along the gut-brain axis can alter bowel physiology and organism behaviour. Colonic sensory neurons activate reflex pathways and give rise to conscious sensation, but the diversity and division of function within these neurons is poorly understood. The identification of signalling pathways contributing to visceral sensation is constrained by a paucity of molecular markers. Here we address this by comprehensive transcriptomic profiling and unsupervised clustering of individual mouse colonic sensory neurons.

DESIGN

Unbiased single-cell RNA-sequencing was performed on retrogradely traced mouse colonic sensory neurons isolated from both thoracolumbar (TL) and lumbosacral (LS) dorsal root ganglia associated with lumbar splanchnic and pelvic spinal pathways, respectively. Identified neuronal subtypes were validated by single-cell qRT-PCR, immunohistochemistry (IHC) and Ca²⁺-imaging.

RESULTS

Transcriptomic profiling and unsupervised clustering of 314 colonic sensory neurons revealed seven neuronal subtypes. Of these, five neuronal subtypes accounted for 99% of TL neurons, with LS neurons almost exclusively populating the remaining two subtypes. We identify and classify neurons based on novel subtype-specific marker genes using single-cell qRT-PCR and IHC to validate subtypes derived from RNA-sequencing. Lastly, functional Ca²⁺-imaging was conducted on colonic sensory neurons to demonstrate subtype-selective differential agonist activation.

CONCLUSIONS

We identify seven subtypes of colonic sensory neurons using unbiased single-cell RNA-sequencing and confirm translation of patterning to protein expression, describing sensory diversity encompassing all modalities of colonic neuronal sensitivity. These results provide a pathway to molecular interrogation of colonic sensory innervation in health and disease, together with identifying novel targets for drug development.

Systematic review with meta-analysis: conditioned pain modulation in patients with the irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is common and is characterised by recurrent abdominal pain, which is a major contributor to healthcare seeking. The neurobiological basis of this pain is incompletely understood. Conditioned pain modulation is a neuromodulatory mechanism through which the brain inhibits the nociceptive afferent barrage through the descending pathways. Reduced conditioned pain modulation has been implicated in the pathophysiology of IBS, although to date only in studies with relatively small sample sizes.

AIM

To clarify the relationship between conditioned pain modulation and IBS by undertaking a systemic review and meta-analysis METHODS: A systematic review of MEDLINE and Web of Science databases was searched (up to 10 May 2018). We included studies examining conditioned pain modulation in adults with IBS and healthy subjects. Data were pooled for meta-analysis to calculate the odds ratio and effect size of abnormal conditioned pain modulation in IBS, with 95% confidence intervals (CI).

RESULTS

The search strategy identified 645 studies, of which 13 were relevant and 12 met the inclusion criteria. Conditioned pain modulation in IBS patients vs healthy subjects was significantly reduced, odds ratio 4.84 (95% CI: 2.19-10.71, P < 0.0001), Hedges' g effect size of 0.85 (95% CI: 0.42-1.28, P < 0.001). There was significant heterogeneity in effect sizes (Q-test χ² = 52, P < 0.001, I² = 78.8%) in the absence of publication bias.

CONCLUSION

Conditioned pain modulation is significantly diminished in patients with IBS vs healthy controls. These data suggest that abnormal descending pathways may play an important pathophysiological role in IBS, which could represent an investigation and a therapeutic target in IBS.

Citrus fruits induced swallow syncope with atrioventricular block or sinus arrest

Swallow syncope is a relatively rare syndrome and caused by various foods and drinks. A 76-year-old man was admitted with frequent syncope while eating. Holter electrocardiogram revealed frequent occurrence of atrioventricular block during meals. Both atrioventricular block and sinus arrest were induced by only eating citrus fruits, citrus jelly, and acidic foods but not by other drinks and foods. These arrhythmias were suppressed after administration of atropine. No further episodes of syncope recurred after the implantation of a DDD pacemaker. This case indicated that acidic stimulation of citrus induced a vasovagal reflex via esophageal nociceptors leading to syncope.

Cortical differences in diverticular disease and correlation with symptom reports

BACKGROUND

Recent studies have shown that the brain of patients with gastrointestinal disease differ both structurally and functionally from that of controls. Highly somatizing diverticular disease (HSDD) patients were also shown to differ from low somatizing (LSDD) patients functionally. This study aimed to investigate how they differed structurally.

METHODS

Four diseases subgroups were studied in a cross-sectional design: 20 patients with asymptomatic diverticular disease (ADD), 18 LSDD, 16 HSDD, and 18 with irritable bowel syndrome. We divided DD patients into LSDD and HSDD using a cutoff of 6 on the Patient Health Questionnaire 12 Somatic Symptom (PHQ12-SS) scale. All patients underwent a 1-mm isotropic structural brain MRI scan and were assessed for somatization, hospital anxiety, depression, and pain catastrophizing. Whole brain volumetry, cortical thickness analysis and voxel-based morphometry were carried out using Freesurfer and SPM.

KEY RESULTS

We observed decreases in gray matter density in the left and right dorsolateral prefrontal cortex (dlPFC), and in the mid-cingulate and motor cortex, and increases in the left (19, 20) and right (19, 38) Brodmann Areas. The average cortical thickness differed overall across groups (P = .002) and regionally: HSDD > ADD in the posterior cingulate cortex (P = .03), HSDD > LSDD in the dlPFC (P = .03) and in the ventrolateral PFC (P < .001). The thickness of the anterior cingulate cortex and of the mid-prefrontal cortex were also found to correlate with Pain Catastrophizing (Spearman's ρ = 0.24, P = .043 uncorrected and Spearman's ρ = 0.25, P = .03 uncorrected).

CONCLUSION & INFERENCES

This is the first study of structural gray matter abnormalities in diverticular disease patients. The data show brain differences in the pain network.

Extra-Intestinal Manifestation of Celiac Disease in Children

The aim of this literature review is to discuss the extra-intestinal manifestations of celiac disease within the pediatric celiac population.

Peripheral KV7 channels regulate visceral sensory function in mouse and human colon

Background

Chronic visceral pain is a defining symptom of many gastrointestinal disorders. The K_V7 family (K_V7.1–K_V7.5) of voltage-gated potassium channels mediates the M current that regulates excitability in peripheral sensory nociceptors and central pain pathways. Here, we use a combination of immunohistochemistry, gut-nerve electrophysiological recordings in both mouse and human tissues, and single-cell qualitative real-time polymerase chain reaction of gut-projecting sensory neurons, to investigate the contribution of peripheral K_V7 channels to visceral nociception.

Results

Immunohistochemical staining of mouse colon revealed labelling of K_V7 subtypes (K_V7.3 and K_V7.5) with CGRP around intrinsic enteric neurons of the myenteric plexuses and within extrinsic sensory fibres along mesenteric blood vessels. Treatment with the K_V7 opener retigabine almost completely abolished visceral afferent firing evoked by the algogen bradykinin, in agreement with significant co-expression of mRNA transcripts by single-cell qualitative real-time polymerase chain reaction for KCNQ subtypes and the B₂ bradykinin receptor in retrogradely labelled extrinsic sensory neurons from the colon. Retigabine also attenuated responses to mechanical stimulation of the bowel following noxious distension (0–80 mmHg) in a concentration-dependent manner, whereas the K_V7 blocker XE991 potentiated such responses. In human bowel tissues, K_V7.3 and K_V7.5 were expressed in neuronal varicosities co-labelled with synaptophysin and CGRP, and retigabine inhibited bradykinin-induced afferent activation in afferent recordings from human colon.

Conclusions

We show that K_V7 channels contribute to the sensitivity of visceral sensory neurons to noxious chemical and mechanical stimuli in both mouse and human gut tissues. As such, peripherally restricted K_V7 openers may represent a viable therapeutic modality for the treatment of gastrointestinal pathologies.

The Rome IV versus Rome III criteria for heartburn diagnosis: A comparative study

BACKGROUND

The phenotypes of heartburn patients are heterogeneous.

OBJECTIVE

The objective of this study was to investigate the proportion of heartburn phenotypes in a Chinese population and to compare the Rome IV and III criteria for heartburn diagnosis.

METHODS

A retrospective study was performed among heartburn patients referred for upper endoscopy and esophageal function tests in a tertiary hospital. Their symptoms fulfilled Rome IV and III criteria.

RESULTS

A total of 233 patients were included. Fifty-nine patients (25%) were diagnosed with esophagitis, 96 (41%) with non-erosive reflux disease (NERD) and 78 (34%) with functional heartburn (FH) based on Rome III criteria. Approximately 70% of the Rome III NERD patients were changed based on Rome IV criteria, with 36 patients (15%) diagnosed with reflux hypersensitivity (RH) and 32 patients (14%) who didn't fulfill the criteria considered unclassified. The FH and RH patients showed higher esophagogastric junction-contractile integral (EGJ-CI) and less hiatal hernia than did Rome IV NERD patients. The unclassified had more hiatal hernias than the FH and RH (p < 0.05). The EGJ-CI was similar between Rome III NERD and FH cases.

CONCLUSION

The Rome IV criteria were stricter for heartburn diagnosis and superior in distinguishing NERD from functional disorders on motility patterns than Rome III.

Celiac Disease Symptom Resolution: Effectiveness of the Gluten-free Diet

OBJECTIVE

The aim of the study was to evaluate the efficacy of the gluten-free diet (GFD) on gastrointestinal (GI) and extra-intestinal (EI) symptom resolution and identify predictors for persistence of symptoms in all celiac patients at the University of Chicago.

METHODS

We conducted a retrospective chart review from 2002 to 2015. GI symptoms included abdominal pain, bloating, constipation, diarrhea, failure to thrive/weight loss, nausea, reflux, and vomiting. EI symptoms included abnormal liver enzymes, arthralgia/arthritis, dermatitis herpetiformis, alopecia, fatigue, headache, anemia, stomatitis, myalgia, psychiatric disorders, rashes, seizures, neuropathy, short stature, delayed puberty, osteoporosis, and infertility.

RESULTS

A total of 554 patients (227 children) with celiac disease (CeD) were included. Abdominal pain, diarrhea and failure to thrive were the most common GI symptoms in children whereas diarrhea, bloating, and abdominal pain were most common in adults. Short stature, fatigue, and headache were the most common EI symptoms in children whereas iron deficiency anemia, fatigue, and headache/psychiatric disorders were most common in adults. Children had significantly higher rates of EI and GI symptom resolution as compared to adults, with greater rates of improvements in GI versus EI symptoms at more than 24 months. Long duration of symptoms, female sex, and non-adherence to a GFD were the most important significant predictors of failure to clinically improve.

CONCLUSIONS

On a strict GFD, children report greater rates of both GI and EI symptom resolution as compared to adults with greater rates of improvement in GI over EI symptoms. Early recognition of CeD and close attention to diet adherence may help in symptom resolution.

Opioid-Induced Constipation and Bowel Dysfunction: A Clinical Guideline

OBJECTIVE

To formulate timely evidence-based guidelines for the management of opioid-induced bowel dysfunction.

SETTING

Constipation is a major untoward effect of opioids. Increasing prescription of opioids has correlated to increased incidence of opioid-induced constipation. However, the inhibitory effects of opioids are not confined to the colon, but also affect higher segments of the gastrointestinal tract, leading to the coining of the term "opioid-induced bowel dysfunction."

METHODS

A literature search was conducted using Medline, EMBASE, and EMBASE Classic, and the Cochrane Central Register of Controlled Trials. Predefined search terms and inclusion/exclusion criteria were used to identify and categorize relevant papers. A series of statements were formulated and justified by a comment, then labeled with the degree of agreement and their level of evidence as judged by the Strength of Recommendation Taxonomy (SORT) system.

RESULTS

From a list of 10,832 potentially relevant studies, 33 citations were identified for review. Screening the reference lists of the pertinent papers identified additional publications. Current definitions, prevalence, and mechanism of opioid-induced bowel dysfunction were reviewed, and a treatment algorithm and statements regarding patient management were developed to provide guidance on clinical best practice in the management of patients with opioid-induced constipation and opioid-induced bowel dysfunction.

CONCLUSIONS

In recent years, more insight has been gained in the pathophysiology of this "entity"; new treatment approaches have been developed, but guidelines on clinical best practice are still lacking. Current knowledge is insufficient regarding management of the opioid side effects on the upper gastrointestinal tract, but recommendations can be derived from what we know at present.

P2Y1R is involved in visceral hypersensitivity in rats with experimental irritable bowel syndrome

AIM

To evaluate the role of P2Y1R in visceral hypersensitivity in rats with experimental irritable bowel syndrome.

METHODS

A rat model of irritable bowel syndrome was generated by intra-colonic administration of acetic acid (AA) and assessed by histology and myeloperoxidase (MPO) activity assay. Then P2Y1R expression in the colonic tissue was detected by Western blot. In order to explore the regulatory role of P2Y1R in visceral hypersensitivity, an agonist (MRS2365) and an antagonist (MRS2179) of P2Y1R were intra-colonically administered and effects were tested through a colorectal distension test. The abdominal withdrawal reflex and abdominal electromyography were tested during the course.

RESULTS

Model assessment tests showed an obvious inflammatory reaction that appeared on the 2^nd d after the AA injection, and the inflammatory reaction gradually recovered and almost disappeared on the 7^th d. The model finished on day 8 and showed a clear feature of IBS that had no organic lesion. The average expression of P2Y1R was significantly higher in the AA group than in the naïve group (0.319 ± 0.02 vs 0.094 ± 0.016, P < 0.001). MRS2365 could effectively raise the colonic hypersensitivity status at intervention doses of 10 (AUC value from 0.30 ± 0.089 to 1.973 ± 0.127 mv·s, P < 0.01) and 100 μmol/L (AUC value from 0.290 ± 0.079 to 1.983 ± 0.195 mv·s, P < 0.01); MRS2179 could effectively reduce the hypersensitivity status at intervention dose of 100 μmol/L (from a mean baseline AUC value of 1.587 ± 0.099 mv·s to 0.140 ± 0.089 mv·s, P < 0.0001). Differences between the MRS2179 group (1.88 ± 1.45) and either the MRS2365 group (3.96 ± 0.19) or the combined treatment (MRS2179 and MRS2365) group (3.28 ± 0.11) were significant (P < 0.01).

CONCLUSION

P2Y1R plays a regulatory role in visceral hypersensitivity in rats with experimental IBS. Specific antagonists of P2Y1R may have potential therapeutic value in treating abdominal pain in IBS.

An acute care approach to functional abdominal pain

Functional abdominal pain disorders are commonly seen in the acute care setting and can be a source of frustration for patients and providers given their inherent chronic nature. However, an understanding of both the general approach to these disorders and the approach to specific common subtypes can help alleviate this frustration and lead to both short-term and long-term therapeutic success. This article describes the pathophysiology of these disorders and outlines a diagnostic and therapeutic approach to commonly seen functional abdominal pain disorders in adults.

Total pancreatectomy for recurrent acute and chronic pancreatitis: a critical review of patient selection criteria

PURPOSE OF REVIEW

Critical review of the indications for total pancreatectomy and highlight limitations in current diagnostic criteria for chronic pancreatitis.

RECENT FINDINGS

The diagnosis of noncalcific chronic pancreatitis remains controversial because of an overreliance on nonspecific imaging and laboratories findings. Endoscopic ultrasound, s-magnetic resonance cholangiopancreatography, and/or endoscopic pancreatic function testing are often used to diagnose noncalcific chronic pancreatitis despite the fact that there is no gold standard for this condition. Abdominal pain is not specific for chronic pancreatitis and is more likely to be encountered in patients with functional gastrointestinal disorders based on the high incidence of these conditions. The duration of pain and opioid analgesic use results in central sensitization that adversely affects pain outcomes after total pancreatectomy. An alcoholic cause is associated with poorer pain outcomes after total pancreatectomy.

SUMMARY

The lack of a gold standard for noncalcific chronic pancreatitis limits the diagnostic accuracy of imaging and laboratory tests. The pain of chronic pancreatitis is nonspecific and is affected by duration, preoperative opioid use, and cause. These factors will need to be considered in the development of future selection criteria for this morbid surgery.

The Role of Esophageal Hypersensitivity in Functional Heartburn

Functional heartburn (FH) is defined as a functional esophageal disorder characterized by symptoms of chronic heartburn with no apparent correlation to acid or nonacid reflux. In addition, its symptoms persist despite the lack of organic abnormalities or inflammation, esophageal motility disorders, or metabolic disorders. Although conditions presenting with esophageal symptoms without endoscopic abnormalities were previously categorized as nonerosive reflux disease, such conditions are now classified into 3 categories under Rome IV criteria: nonerosive reflux disease, reflux hypersensitivity, and FH. Although many aspects of FH remain unclear, its onset mechanism is considered to be strongly associated with peripheral or central sensitization, given the fact that its symptoms seem to be unrelated to gastroesophageal reflux. In addition, the cause of such hypersensitivity is an interesting topic in itself, and psychological factors, such as stress followed by increasing esophageal permeability are gaining attention as factors that can potentially influence this condition. There is a great unmet clinical need for therapeutic drugs that can be used to treat FH, and the development of novel drugs, diagnostic tests and biomarkers is eagerly awaited.

Possible Role of the Myelinated Neural Network in the Parietal Peritoneum in Rats as a Mechanoreceptor

A network of myelinated nerve fibers in the peritoneum covers the abdominal wall. We studied the topographic distribution of this network, explored the fibers' destination in the central nervous system, and examined the markers in these fibers in order to identify the nature of the sensation conveyed by the network of nerve fibers in rats. We used Sihler's method, which stains myelinated fibers in whole mount materials, and observed a dense nerve network and endings toward the peritoneal cavity in the peritoneum that covers the abdomen's lateral bulge. We studied the axonal transport of cholera toxin subunit B to investigate the central projections of this network in order to identify its function. After applying the tracer in the peritoneum, we observed many labeled terminals in the medial part of laminae 3-5 of the spinal cord. A small number of labeled terminals was observed in the dorsal nucleus of Clarke and gracile nucleus. Labeled somata were observed in the dorsal root ganglia (DRG). Most (96%) were larger than 35 μm. We performed immunohistochemistry of the abdominal wall, using antiserum against the 200-kD neurofilament (a marker for mechanosensory neurons). We observed many positive nerve fibers in the peritoneum. Because cell bodies in the DRG were large, their nerve terminals ended in the base of the dorsal horn, which is known to transmit proprioceptive information, and the network possesses the marker for mechanosensitive fibers; therefore, it appears that the myelinated nerve network conveys information about distension and/or contraction of the abdominal wall. Anat Rec, 300:1662-1669, 2017. © 2017 Wiley Periodicals, Inc.

Neuroimmune factors in functional gastrointestinal disorders: A focus on irritable bowel syndrome

BACKGROUND

Abnormal abdominal pain perception is the most bothersome and difficult to treat symptom of functional gastrointestinal disorders (FGIDs). Visceral pain stimuli are perceived and transmitted by afferent neurons residing in the dorsal root ganglia that have sensory nerve endings in the gut wall and mesentery. Accumulating evidence indicates that peripheral activation and sensitization of these sensory nerve endings by bioactive mediators released by activated immune cells, in particular mast cells, can lead to aberrant neuroimmune interactions and the development and maintenance of visceral hypersensitivity. Besides direct neuronal activation, low concentrations of proteases, histamine, and serotonin can chronically sensitize nociceptors, such as TRP channels, leading to persistent aberrant pain perception.

PURPOSE

This review discusses the potential mechanisms underlying aberrant neuroimmune interactions in peripheral sensitization of sensory nerves. A better understanding of the cells, mediators, and molecular mechanisms triggering persistent aberrant neuroimmune interactions brings new insights into their contribution to the physiology and pathophysiology of visceral pain perception and provides novel opportunities for more efficient therapeutic treatments for these disorders.

The Role of Esophageal Hypersensitivity in Functional Esophageal Disorders

The Rome IV diagnostic criteria delineates 5 functional esophageal disorders which include functional chest pain, functional heartburn, reflux hypersensitivity, globus, and functional dysphagia. These are a heterogenous group of disorders which, despite having characteristic symptom profiles attributable to esophageal pathology, fail to demonstrate any structural, motility or inflammatory abnormalities on standard clinical testing. These disorders are associated with a marked reduction in patient quality of life, not least considerable healthcare resources. Furthermore, the pathophysiology of these disorders is incompletely understood. In this narrative review we provide the reader with an introductory primer to the structure and function of esophageal perception, including nociception that forms the basis of the putative mechanisms that may give rise to symptoms in functional esophageal disorders. We also discuss the provocative techniques and outcome measures by which esophageal hypersensitivity can be established.

Esophageal acid sensitivity and mucosal integrity in patients with functional heartburn

BACKGROUND

Patients with functional heartburn (FH) experience troublesome heartburn that is not related to gastroesophageal reflux. The etiology of the heartburn sensation in FH patients is unknown. In patients with reflux disease, esophageal hypersensitivity seems associated with impaired mucosal integrity. We aimed to determine esophageal sensitivity and mucosal integrity in FH and non-erosive reflux disease (NERD) patients.

METHODS

In this prospective experimental study, we performed an acid perfusion test and upper endoscopy with biopsies in 12 patients with NERD and nine patients with FH. Mucosal integrity was measured during endoscopy using electrical tissue impedance spectroscopy and biopsy specimens were analyzed in Ussing chambers for transepithelial electrical resistance and transepithelial permeability.

KEY RESULTS

Lag time to heartburn perception was significantly longer in FH patients (median 12 min) than in NERD patients (median 3 min). Once perceived, intensity of heartburn was scored equal with median visual analog scale 6.5 and 7.1 respectively. Esophageal mucosal integrity was also comparable between FH and NERD patients, both in vivo extracellular impedance and ex vivo transepithelial resistance and permeability were similar.

CONCLUSIONS & INFERENCES

Patients with FH did not show acid hypersensitivity as seen in patients with NERD. However, once perceived, intensity of heartburn is similar. Esophageal mucosal integrity is similar between NERD and FH patients, and is therefore unlikely to be the underlying cause of the observed difference in esophageal acid perception.

Understanding the sensory irregularities of esophageal disease

Symptoms relating to esophageal sensory abnormalities can be encountered in the clinical environment. Such sensory abnormalities may be present in demonstrable disease, such as erosive esophagitis, and in the ostensibly normal esophagus, such as non-erosive reflux disease or functional chest pain. In this review, the authors discuss esophageal sensation and the esophageal pain system. In addition, the authors provide a primer concerning the techniques that are available for investigating the autonomic nervous system, neuroimaging and neurophysiology of esophageal sensory function. Such technological advances, whilst not readily available in the clinic may facilitate the stratification and individualization of therapy in disorders of esophageal sensation in the future.