Rectal Balloon Distension Research Articles

Impact of SCN10A Polymorphism on Abdominal Pain Perception and Visceral Hypoalgesia in Crohn's Disease and Ulcerative Colitis.

Hypoalgesic inflammatory bowel disease (IBD) may provide critical insights into human abdominal pain. This condition was previously associated with homozygosity for a polymorphism (rs6795970,A1073V;1073val/val) related to Nav1.8, a voltage-gated sodium channel preferentially expressed on nociceptors. It was unclear whether this relationship existed for both Crohn's disease (CD) and ulcerative colitis (UC). This study evaluated a larger, carefully phenotyped IBD cohort to investigate this question. Allelic and genotypic frequencies of rs6795970 were compared among study cohorts characterized by concomitant assessment of intestinal inflammatory status and abdominal pain experience. Visceral sensory perception was performed in healthy individuals using rectal balloon distension(RBD). We analyzed 416 IBD patients (261CD:155UC) and 142 healthy controls. In the IBD cohort, 84 individuals (43CD:41UC) were determined to have hypoalgesic disease. The allelic frequency of rs6795970 was significantly higher in hypoalgesic IBD patients when compared to other IBD patients and healthy controls. Hypoalgesic IBD patients were also more likely to be homozygous for this polymorphism when compared to other IBD patients and healthy controls. Hypoalgesic CD (30%vs.12%,p=0.004) and hypoalgesic UC (32%vs.15%,p=0.036) were each significantly more likely to be associated with homozygosity for the rs6795970 polymorphism. In a cohort of healthy individuals(n=50), rs6795970 homozygotes(n=11) also demonstrated reduced abdominal discomfort to RBD. These findings indicate that Nav1.8 plays a key role in human visceral pain perception, and could serve as a novel diagnostic target in the management of hypoalgesic CD and UC, and potential therapeutic target for conditions associated with chronic abdominal pain.

Anorectal function and symptoms 6 months after robot-assisted laparoscopic radical prostatectomy: a single-center study.

Robot-assisted laparoscopic radical prostatectomy (RALP) is a common procedure for the treatment of localised prostate cancer. Anorectal symptoms such as fecal incontinence (FI), rectal urgency or disturbed defecation have been reported after the operation. Anorectal function is dependent on the integrity of anal and pelvic nerves and muscles, rectal sensory function as well as rectal reservoir function. The aim of this study was to investigate the potential influence of RALP on anorectal physiological function and bowel symptoms. In this pilot study, 29 patients with localised prostate cancer scheduled for RALP were included. Anorectal physiology was used to measure rectal sensitivity and reservoir function as well as anal sphincter pressures. Bowel symptoms were measured by a bowel function questionnaire and a 2-week bowel function diary. Measurements were done before the operation and repeated at 6 months after the operation. The study observed a significant postoperative increase in rectal sensory threshold for rectal balloon distention, from 20 to 40 mmHg, P < 0.001. This change is indicative of a decrease in rectal sensation after RALP. There were no other statistical significant differences in any of the physiological tests performed. Importantly, there was no change in any of the bowel symptoms after surgery. This study showed that RALP may lead to impaired rectal sensory function. This finding did not, however, seem to have any influence on the patients´ postoperative clinical bowel function.

Do we perceive sensations inside and outside of our body differently? Perceptual, emotional, and behavioral differences between visceral and somatic sensation, discomfort, and pain.

Experimental research evaluating differences between the visceral and somatic stimulation is limited to pain and typically uses different induction methods for visceral and somatic stimulation (e.g., rectal balloon distention vs. tactile hand stimulation). Our study aimed to compare differences in response time, intensity, unpleasantness, and threat between identical electrical visceral and somatic stimulations at both painful and non-painful perceptual thresholds. Electrical stimulation was applied to the wrist and distal esophagus in 20 healthy participants. A double pseudorandom staircase determined perceptual thresholds of Sensation, Discomfort, and Pain for the somatic and visceral stimulations, separately. Stimulus reaction time (ms, via button press), and intensity, unpleasantness, and threat ratings were recorded after each stimulus. General linear mixed models compared differences in the four outcomes by stimulation type, threshold, and the stimulation type-by-threshold interaction. Sigmoidal maximum effect models evaluated differences in outcomes across all delivered stimulation intensities. Overall, visceral stimulations were perceived as more intense, threatening, and unpleasant compared to somatic stimulations, but participants responded faster to somatic stimulations. There was no significant interaction effect, but planned contrasts demonstrated differences at individual thresholds. Across all delivered intensities, higher intensity stimulations were needed to reach the half-maximum effect of self-reported intensity, unpleasantness, and threat ratings in the visceral domain. Differences exist between modalities for both non-painful and painful sensations. These findings may have implications for translating paradigms and behavioral treatments from the somatic domain to the visceral domain, though future research in larger clinical samples is needed.

Rectal sensitivity correlated with gastrointestinal-mediated glucose disposal, but not the incretin effect.

The mechanisms behind the diminished incretin effect in type 2 diabetes are uncertain, but impaired vagal transmission has been suggested. We aimed to investigate the association between the incretin effect and autonomic neuropathy, and the degree of dysglycaemia and duration of diabetes. For a cross-sectional study, we included participants with either longstanding type 2 diabetes, recent onset, untreated diabetes and controls without diabetes matched for age, sex and body mass index. Autonomic nerve function was assessed with cardiovascular reflex tests, heart rate variability and sudomotor function. Visceral afferent nerves in the gut were tested performing rapid rectal balloon distention. An oral glucose tolerance test and an intravenous isoglycaemic glucose infusion were performed to calculate the incretin effect and gastrointestinal-mediated glucose disposal (GIGD). Sixty-five participants were recruited. Participants with diabetes had rectal hyposensitivity for earliest sensation (3.7 ± 1.1 kPa in longstanding, 4.0 ± 1.3 in early), compared to controls (3.0 ± 0.9 kPa), p = .005. Rectal hyposensitivity for earliest sensation was not associated with the incretin effect (rho = -0.204, p = .106), but an association was found with GIGD (rho -0.341, p = .005). Incretin effect and GIGD were correlated with all glucose values, HbA1c and duration of diabetes. Rectal hyposensitivity was uncovered in both longstanding and early type 2 diabetes, and was not associated with the incretin effect, but with GIGD, implying a potential link between visceral neuropathy and gastrointestinal handling of glucose. Both the incretin effect and GIGD were associated with the degree of dysglycaemia and the duration of diabetes. Some of the data have previously been published and presented as a poster on the American Diabetes Association 83rd Scientific Sessions: Meling etal; 1658-P: Rectal Hyposensitivity, a Potential Marker of Enteric Autonomic Nerve Dysfunction, Is Significantly Associated with Gastrointestinally Mediated Glucose Disposal in Persons with Type 2 Diabetes. Diabetes 20 June 2023; 72 (Supplement_1): 1658-P. https://doi.org/10.2337/db23-1658-P.

The Composite Autonomic Symptom Score 31 Questionnaire: A Sensitive Test to Detect Risk for Autonomic Neuropathy.

Autonomic neuropathy is a common but often neglected complication of diabetes, prediabetes, and even in individuals with an elevated risk of diabetes. The Composite Autonomic Symptom Score (COMPASS) 31 is a validated and easy-to-use questionnaire regarding autonomic symptoms. We aimed to use a digitally, Norwegian version of the COMPASS 31 in people with different durations of diabetes and healthy controls to consider feasibility and to investigate if scores could discriminate between positive and negative outcomes for established tests for diabetic neuropathy, including cardiovascular autonomic neuropathy (CAN) and a novel method of examining the gastrointestinal visceral sensitivity. We included 21 participants with longstanding type 2 diabetes, 15 with early type 2 diabetes, and 30 matched controls. The mean age for all groups was 69 years. Participants were phenotyped by cardiovascular autonomic reflex tests, electrical skin conductance, sural nerve electrophysiology, and the monofilament test. As a proxy for gastrointestinal visceral and autonomic nerve function, evoked potentials were measured following rapid rectal balloon distention. Participants with longstanding diabetes scored a median (IQR) of 14.9 (10.8-28.7) points, early diabetes of 7.3 (1.6-15.2), and matched controls of 8.6 (4.1-21.6), p = 0.04. Women and men scored 14.4 (5.5-28.7) and 7.8 (3.6-14.6) points, respectively, p = 0.01. Participants with definite or borderline CAN scored 14.3 (10.4-31.9) points, compared to participants with no CAN, 8.3 (3.2-21.5), p = 0.04. Lowering the diagnostic cut-off from 16 to 10 points increased the sensitivity from 0.33 to 0.83, with a decreased specificity from 0.68 to 0.55. We successfully used COMPASS 31 in Norwegian. Thus, following the guidelines, we suggest clinical implementation for the assessment of autonomic neuropathy. Participants with longstanding diabetes had an increased likelihood of symptoms and signs of autonomic neuropathy. For screening purposes, the sensitivity was improved by lowering the cut-off to 10 points, with a lower score nearly excluding the diagnosis.

1658-P: Rectal Hyposensitivity, a Potential Marker of Enteric Autonomic Nerve Dysfunction, Is Significantly Associated with Gastrointestinally Mediated Glucose Disposal in Persons with Type 2 Diabetes

The incretin effect in type 2 diabetes is reduced, but the mechanisms behind are uncertain. We hypothesized that the incretin effect associates with degree of enteric autonomic nerve dysfunction and evaluated gastrointestinally mediated glucose disposal (GIGD), as a proxy for the incretin effect, and rectal sensitivity to mechanical distension representing afferent gut signalling. Sixty-six participants with either 1) longstanding type 2 diabetes, 2) newly onset (&amp;lt;1 year), medically untreated diabetes, or 3) healthy controls, underwent a 75 g oral glucose tolerance test (OGTT) and an intravenous isoglycemic glucose infusion to determine GIGD. Earliest sensation to rectal rapid balloon distention was determined as a proxy for autonomic neuropathy. Compared to controls (59.3±14.4%), GIGD was reduced in both early (36.4±14.7%) and longstanding diabetes (17.4±22.3%), with significant difference between all three groups (P&amp;lt;0.01). Both groups of diabetes needed higher pressure during rapid rectal balloon distention (3.7±1.1 kPa for longstanding diabetes, 4.0±1.3 for early diabetes), compared to controls (3.0±0.9 kPa, P&amp;lt;0.01), with no significant difference between the two diabetes groups. GIGD was inversely correlated with pressure at earliest sensation (rho 0.341, P&amp;lt;0.01). For those needing a pressure between 1 and 3 kPa and between 4 and 7 kPa, respectively, GIGD was 46.2%±24.9 and 34.4±23.9% (P=0.05). GIGD was inversely and significantly correlated with glucose values during OGTT, with strongest correlation to the 90-minute value (rho 0.873, P&amp;lt;0.01), and HbA1c (rho 0.653, P&amp;lt;0.01). We show that the degree of rectal hyposensitivity correlates with reduced GIGD and confirm that GIGD correlates with the degree of dysglycemia. These results warrant further studies on the potential role of gut autonomic dysfunction in the reduced incretin effect characterizing type 2 diabetes. Disclosure S.Meling: Consultant; Novo Nordisk, Lilly, AstraZeneca, Boehringer-Ingelheim, Sanofi. E.Tjora: None. N.Ejskjaer: None. S.Carlsen: None. F.K.Knop: Advisory Panel; AstraZeneca, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk, Sanofi, Consultant; AstraZeneca, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk, Sanofi, Research Support; Novo Nordisk, Zealand Pharma A/S, Speaker's Bureau; AstraZeneca, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk, Sanofi, Lundbeck. P.Njølstad: None. C.Brock: Research Support; Abbott, ElectroCore. R.B.Nedergaard: Other Relationship; Grünenthal Group. E.Søfteland: None. Funding Helse Vest, Norway (F-11637/4800002072); Johan Selmer Kvanes Legat (Legacy)

The PanGut-study: Evoked potentials following rectal balloon distention, a way of evaluating diabetic autonomic neuropathy in the gut?

AimThere is a lack of methods for investigating the autonomic nerves of the gastrointestinal tract. Our aim was to explore a novel test measuring visceral sensory evoked potentials (EPs) in response to rapid balloon distention in the rectum and compare it to established tests for diabetic neuropathy. MethodParticipants with longstanding type 2 diabetes, newly onset, untreated diabetes <1 year, and matched controls, were included. Tests included cardiovascular reflex tests, orthostatic blood pressure, electrical skin conductance assessment, sural nerve testing and monofilament test. The rectal balloon distention pressure at earliest sensation and threshold of unpleasantness were identified and used to elicit mechanical EPs. ResultsThe pressure at earliest sensation was higher in people with diabetes, 0.038 (0.012) bar vs. controls 0.030 (0.009) bar, p = 0.002, and in people with signs of peripheral neuropathy, 0.045 (0.014) bar, p < 0.01. Clinical correlations between EP amplitude and latency, and other tests were found. ConclusionsRectal hyposensitivity was associated with both longstanding and early diabetes, indicating enteric sensory dysfunction already in early stages of diabetes. Correlation analyses may indicate that central afferent processing is affected in parallel with peripheral neuronal function.

Sensory brain activation during rectal balloon distention: a pilot study in healthy volunteers to assess safety and feasibility at 1.5T

ObjectiveAlthough increasing evidence suggests a central mechanism of action for sacral neuromodulation, the exact mechanism remains unclear. We set up a scanning paradigm to measure brain activation related to various stages of rectal filling using rectal balloon distention.Materials and MethodsSix healthy volunteers underwent rectal balloon distention during MRI scanning at a 1.5T scanner with a Tx/Rx head coil. MR images were collected at four levels of distention: empty balloon (EB), first sensation volume (FSV), desire to defecate volume (DDV), maximum tolerable volume (MTV). Data were analyzed using BrainVoyager 20.4. Whole brain and ROI-based fixed-effects general linear model analyses were performed on the fMRI time-course data from all participants.ResultsRectal filling until FSV evoked the most blood-oxygen-level-dependent responses in several clusters throughout the cortex, followed by the responses evoked by rectal filling until DDV. Interestingly, rectal filling until MTV evoked negative responses compared to baseline throughout the cortex. No negative side effects were found.DiscussionThis study shows that a standardized paradigm for functional MRI combined with rectal filling is feasible and safe in healthy volunteers and is ready to be used in fecal incontinent patients to assess whether their brain activity differs from healthy controls.

A Pilot Study of Clinical Evaluation and Formation Mechanism of Irritable Bowel Syndrome-like Symptoms in Inflammatory Bowel Disease Patients in Remission.

Background/AimsSome inflammatory bowel disease (IBD) patients in remission suffer from irritable bowel syndrome (IBS)-like symptoms (IBD-IBS). The pathogenesis has not yet been elucidated. The study aim is to evaluate relationships among quality of life (QOL), psychological status, and visceral sensitivity, and explore the formation mechanism of IBD-IBS.MethodsForty-seven patients with Crohn’s disease in remission, 24 ulcerative colitis in remission, 26 IBS, and 20 healthy controls were included in the study. The abdominal pain, QOL, anxiety, and depression were evaluated through questionnaires. Visceral sensitivity was measured by rectal balloon distension. The serum levels of 5-hydroxytryptamine (5-HT) and nerve growth factor (NGF) were measured by enzyme-linked immunosorbent assay. The expressions of tryptase, 5-HT, NGF, and related receptors in colonic tissues were detected by immunohistochemistry and western blot.ResultsPrevalence of IBS-like symptoms in Crohn’s disease and ulcerative colitis patients in clinical remission was 29.8% and 50.0%, respectively. The QOL was lower, the anxiety/depression scores were higher in IBD-IBS patients than those without IBS-like symptoms. Additionally, patients with IBD-IBS existed visceral hypersensitivity. Besides, abdominal pain was associated with poor QOL, visceral hypersensitivity, anxiety, and depression in IBD-IBS patients. The number of mast cells (MCs) and expressions of 5-HT, NGF, and related receptors were higher in IBD-IBS patients than those with no such symptoms. The serum levels of 5-HT and NGF positively correlated with abdominal pain and visceral hypersensitivity.ConclusionIBD-IBS patients may have low QOL and psychological abnormalities, as wells as visceral hypersensitivity which may be related to increased 5-HT and NGF levels released from activated mast cells.

Association between pain sensitivity and gray matter properties in the sensorimotor network in women with irritable bowel syndrome.

BackgroundEnhanced perception of visceral stimuli is an important feature of Irritable Bowel Syndrome (IBS), but it is not known whether visceral sensitivity is associated with regional structural brain properties in IBS.MethodsStructural brain magnetic resonance imaging data from 216 women with IBS and 138 healthy women were parcellated with FreeSurfer to define regional gray matter morphometry (volume, cortical thickness, surface area and mean curvature) in the sensorimotor network. General linear models were used to detect group differences between IBS and health. In a second set of 48 female IBS patients, pain threshold, pain intensity ratings during rectal balloon distension, and reported levels of abdominal pain and bloating were correlated with brain regions that showed differences between IBS and health in the first data set.Key ResultsSeveral statistically significant differences between IBS patients and healthy controls were found, mainly higher gray matter volume and cortical thickness in primary somatosensory cortex, secondary somatosensory cortex, and subcortical regions, and lesser gray matter volume, surface area and cortical thickness in posterior insula and superior frontal gyrus. Pain intensity ratings during rectal distension were associated with left primary somatosensory cortical thickness, and pain threshold was associated with right nucleus accumbens volume.Conclusions and InferencesRegional gray matter differences in sensorimotor network are associated with visceral sensitivity and may represent neuroplastic changes in female IBS patients.

Visceral hypersensitivity is together with psychological distress and female gender associated with severity of IBS-like symptoms in quiescent ulcerative colitis.

A subset of ulcerative colitis (UC) patients in remission demonstrate IBS-like symptoms. Visceral hypersensitivity is a key pathophysiological mechanism in IBS, but its relevance to IBS-like symptoms in inactive UC remains unclear. UC patients in remission (UCR) were screened for IBS-like symptoms. Rectal sensitivity was assessed with rectal balloon distensions, with determination of sensory thresholds and unpleasantness/pain intensity ratings. Patients completed questionnaires evaluating gastrointestinal (GI) and psychological symptoms. Age- and gender-matched IBS subjects and healthy controls (HC) also underwent a rectal sensitivity test. We included 36 UCR patients (18 with IBS-like symptoms (UCR+IBS) and 18 without (UCR-IBS)), 36 IBS subjects, and 14 HC. UCR and IBS patients were more sensitive to rectal balloon distensions than HC, but no differences between UCR and IBS patients were observed. UCR+IBS patients had lower sensory thresholds and higher unpleasantness ratings than UCR-IBS. In UCR patients, the overall GI symptom severity, pain, and bloating, but not diarrhea, constipation or satiety, were associated with rectal sensitivity. In multivariate analyses, rectal sensitivity, psychological distress, and female gender were identified as factors independently associated with GI symptom severity. 61% of UCR patients demonstrated rectal hypersensitivity, and these patients more commonly reported at least mild bloating and pain, and overall GI symptoms, compared to those with normal rectal sensitivity. Visceral hypersensitivity was associated with IBS-like symptoms, in particular pain and bloating, in inactive UC. Together with psychological factors and female gender, visceral hypersensitivity seems to be involved in GI symptom generation in quiescent UC.

Rectal Distension Increased the Rectoanal Gradient in Patients with Normal Rectal Sensory Function.

Frequent observation of abnormal manometric patterns consistent with dyssynergia in healthy volunteers has warranted the need for reassessment of the current methods to enhance the diagnostic value of anorectal manometry in functional defecatory disorders. Whether rectal distention at simulated evacuation will affect anorectal pressure profile and increase rectoanal gradient is not known. One hundred and eight consecutive patients with chronic constipation, 93 females, median age 53years (interquartile range: 40-65), were studied. Simulated evacuation was performed firstly with empty balloon and subsequently after balloon distention to 50 and 100ml. Anorectal pressures were compared. We also performed subgroup analysis in relation to outcome of balloon expulsion test (BET). In addition, we studied the effect of rectal distension on the rectoanal pressure gradient with respect to rectal sensory function. Rectal balloon distension at simulated evacuation improved rectoanal gradient and decreased the rate of dyssynergia during high-resolution anorectal manometry. In subgroup analysis, the increase in rectoanal gradient and correction of dyssynergia with rectal distension was limited to the patients who had normal BET and normal rectal sensory function. Rate of anal relaxation, residual anal pressures, and rectoanal gradient were significantly different between patients with and without normal BET at 50ml of rectal distension. Rectoanal gradient recorded only after rectal distension, along with BMI and maximum tolerable volumes, could predict BET results independently in patients with chronic constipation. Rectal distension during simulated evacuation will affect the anorectal pressure profile. Increase in rectoanal gradient and correction of dyssynergia was only significant in patients with normal rectal sensory function and normal BET.

Effect of gender on the etiology of fecal incontinence: Retrospective analysis of a tertiary referral center in Turkey.

Anorectal diseases, including fecal incontinence, are prevalent and have an enormous impact on the quality of life. Therefore, investigating their etiological factors may help to reduce the incidence and/or the severity of the underlying diseases. Referral complaints (constipation, strained defecation, and incontinence) and medical and anorectal manometry records of 883 (562 female/321 male, ages 45.17±1.00 and 48.41±0.63 years, respectively) patients were evaluated retrospectively. Maximal resting pressure (MRP) and maximal squeeze pressure (MSP) measured by stationary pull-through technique, volume of rectoanal inhibitory reflex, and sensory threshold to rectal balloon distention (ST) were obtained by water perfusion system. Data were compared according to referral complaints, age, gender, parity, and underlying diseases. Incontinence was the most frequent referral complaint in 61.2% of females and 67.6% of males. MRP and MSP were significantly lower in incontinent females than in the other groups. In incontinent males, MSP was lower than the strained defecation group, and ST was higher than the constipation group. Age was negatively correlated with MRP for both of the genders and in all groups. Obstetric trauma (85%) and number of parity (3.40±2.59) were significantly higher in incontinent females. Moreover, the most prevalent underlying disease was diabetes in incontinent females (13.7%) and neurological diseases, including traumas, in incontinent males (41.5%). Increasing awareness of labor safety, controlling diabetes mellitus, and preventing obstetric traumas may reduce the prevalence of fecal incontinence.

Are there sex differences in visceral sensitivity in young healthy men and women?

Visceral hypersensitivity plays a key role in the pathophysiology of chronic visceral pain like irritable bowel syndrome (IBS), which is significantly more prevalent in women. Possible sex differences in visceral sensitivity remain poorly studied. We assessed sex differences in visceral sensitivity and their association with subclinical symptoms, trait anxiety, and chronic stress in a large sample of healthy men and women. In 280 young healthy volunteers (50% female), visceral sensory and pain thresholds were determined using rectal balloon distensions. Gastrointestinal (GI) symptoms, chronic stress, and trait anxiety as IBS-related risk factors were assessed with questionnaires. Men and women were compared regarding visceral sensitivity and multiple regression analyses were conducted to evaluate the predictive value of sex and risk factors for visceral sensitivity. Subgroups with high, intermediate, and low sensitivity were compared regarding psychological and biological characteristics. Men and women did not differ in sensory or pain thresholds or in IBS-related risk factors. In multiple regression analyses, no predictor of visceral sensitivity could be identified. While sensitivity subgroups differed in sensory and pain thresholds, the proportions of men and women were comparable, and groups did not differ in IBS-related risk factors. Despite the large sample size, we found no evidence supporting sex differences in visceral sensitivity. At least in healthy young volunteers, our findings suggest that sex, GI symptoms, anxiety, or chronic stress do not contribute to altered visceral sensitivity.

Visceral sensitivity remains stable over time in patients with irritable bowel syndrome, but with individual fluctuations.

Visceral hypersensitivity in irritable bowel syndrome (IBS), measured with rectal balloon distensions, using a barostat, has been suggested to be a phenomenon that is reduced due to habituation at repeated investigations. We investigated the stability of rectal sensitivity in patients with IBS who had undergone a previous rectal barostat study and assessed variations in symptom pattern and severity in relation to rectal sensory function. Irritable bowel syndrome patients, who had previously been undergone a rectal barostat study, were included. All patients underwent a second study 8-12years later. Symptoms were characterized by use of questionnaires. We included 26 subjects (17 females, median age at the index investigation 44.5 (21-61) years). Pressure and volume sensory thresholds were unchanged at the follow-up compared with the index investigation (P>0.05 for all). At the index investigation, 8/26 patients had rectal hypersensitivity of which four were reclassified as normosensitive, and sixfrom normo- to hypersensitive, meaning that 10/26 patients were hypersensitive at the follow-up investigation. IBS-QOL had improved significantly in six of nine domainsat follow-up (P<0.05 for all). There were no differences in anxiety, depression, IBS symptom severity, or somatization (P>0.05) at follow-up. None of these were associated with change in rectal sensitivity at follow-up. Rectal hypersensitivity and IBS symptoms remained stable at the group level over 8-12years in IBS patients, even though individual fluctuations were noted. Our findings contradict previous findings indicating that visceral hypersensitivity is an unstable trait.

Evidence for an association of gut microbial Clostridia with brain functional connectivity and gastrointestinal sensorimotor function in patients with irritable bowel syndrome, based on tripartite network analysis

Background and aimsEvidence from preclinical and clinical studies suggests that interactions among the brain, gut, and microbiota may affect the pathophysiology of irritable bowel syndrome (IBS). As disruptions in central and peripheral serotonergic signaling pathways have been found in patients with IBS, we explored the hypothesis that the abundance of serotonin-modulating microbes of the order Clostridiales is associated with functional connectivity of somatosensory brain regions and gastrointestinal (GI) sensorimotor function.MethodsWe performed a prospective study of 65 patients with IBS and 21 healthy individuals (controls) recruited from 2011 through 2013 at a secondary/tertiary care outpatient clinic in Sweden. Study participants underwent functional brain imaging, rectal balloon distension, a nutrient and lactulose challenge test, and assessment of oroanal transit time within a month. They also submitted stool samples, which were analyzed by 16S ribosomal RNA gene sequencing. A tripartite network analysis based on graph theory was used to investigate the interactions among bacteria in the order Clostridiales, connectivity of brain regions in the somatosensory network, and GI sensorimotor function.ResultsWe found associations between GI sensorimotor function and gut microbes in stool samples from controls, but not in samples from IBS patients. The largest differences between controls and patients with IBS were observed in the Lachnospiraceae incertae sedis, Clostridium XIVa, and Coprococcus subnetworks. We found connectivity of subcortical (thalamus, caudate, and putamen) and cortical (primary and secondary somatosensory cortices) regions to be involved in mediating interactions among these networks.ConclusionsIn a comparison of patients with IBS and controls, we observed disruptions in the interactions between the brain, gut, and gut microbial metabolites in patients with IBS—these involve mainly subcortical but also cortical regions of brain. These disruptions may contribute to altered perception of pain in patients with IBS and may be mediated by microbial modulation of the gut serotonergic system.

Characterization of Simultaneous Pressure Waves as Biomarkers for Colonic Motility Assessed by High-Resolution Colonic Manometry.

Simultaneous pressure waves (SPWs) in manometry recordings of the human colon have been associated with gas expulsion. Our hypothesis was that the SPW might be a critical component of most colonic motor functions, and hence might act as a biomarker for healthy colon motility. To that end, we performed high-resolution colonic manometry (HRCM), for the first time using an 84-sensor (1 cm spaced) water-perfused catheter, in 17 healthy volunteers. Intraluminal pressure patterns were recorded during baseline, proximal and rectal balloon distention, after a meal and following proximal and rectal luminal bisacodyl administration. Quantification was performed using software, based on Image J, developed during this study. Gas expulsion was always associated with SPWs, furthermore, SPWs were associated with water or balloon expulsion. SPWs were prominently emerging at the termination of proximal high amplitude propagating pressure waves (HAPWs); we termed this motor pattern HAPW-SPWs; hence, SPWs were often not a pan-colonic event. SPWs and HAPW-SPWs were observed at baseline with SPW amplitudes of 12.0 ± 8.5 mmHg and 20.2 ± 7.2 mmHg respectively. The SPW occurrence and amplitude significantly increased in response to meal, balloon distention and luminal bisacodyl, associated with 50.3% anal sphincter relaxation at baseline, which significantly increased to 59.0% after a meal, and 69.1% after bisacodyl. Often, full relaxation was achieved. The SPWs associated with gas expulsion had a significantly higher amplitude compared to SPWs without gas expulsion. SPWs could be seen to consist of clusters of high frequency pressure waves, likely associated with a cluster of fast propagating, circular muscle contractions. SPWs were occasionally observed in a highly rhythmic pattern at 1.8 ± 1.2 cycles/min. Unlike HAPWs, the SPWs did not obliterate haustral boundaries thereby explaining how gas can be expelled while solid content can remain restrained by the haustral boundaries. In conclusion, the SPW may become a biomarker for normal gas transit, the gastrocolonic reflex and extrinsic neural reflexes. The SPW assessment reveals coordination of activities in the colon, rectum and anal sphincters. SPWs may become of diagnostic value in patients with colonic dysmotility.

The impact of naloxegol on anal sphincter function - Using a human experimental model of opioid-induced bowel dysfunction

Background and aimsOpioid treatment interferes with anal sphincter function and its regulation during defecation. This may result in straining, incomplete evacuation, and contribute to opioid-induced bowel dysfunction (OIBD). Employing an experimental model of oxycodone-induced OIBD, we hypothesized that co-administration of the peripherally acting μ-opioid antagonist naloxegol would improve anal sphincter function in comparison to placebo. MethodsIn a double-blind randomized crossover trial, 24 healthy males were assigned to a six-day treatment of oral oxycodone 15 mg twice daily in combination with either oral naloxegol 25 mg once daily or placebo. At baseline and at day 6, anal resting pressure and the recto-anal inhibitory reflex (RAIR) were evaluated using manometry and rectal balloon distension. Furthermore, the functional lumen imaging probe was used to measure distensibility of the anal canal. Gastrointestinal symptoms were assessed with the Patient Assessment of Constipation Symptom (PAC-SYM) questionnaire and the Bristol Stool Form Scale. ResultsDuring oxycodone treatment, naloxegol improved RAIR-induced sphincter relaxation by 15% (−45.9 vs −38.8 mm Hg; P < 0.01). No differences in anal resting pressure and anal canal distensibility were found between treatments (all P > 0.5). Naloxegol improved PAC-SYM symptoms (mean score over days; 2.6 vs 4.5, P < 0.001) and improved stool consistency scores (mean score over days; 3.3 vs 2.9, P < 0.01). ConclusionsIn this experimental model of OIBD, naloxegol improved the RAIR and reduced gastrointestinal symptoms. Hence, in contrast to conventional laxatives, naloxegol may regulate opioid-induced anal sphincter dysfunction and facilitate the defecation process.

High-resolution anorectal manometry in children with functional constipation: a single-centre experience before and after treatment.

IntroductionConstipation is a common disorder among children, and most of the cases are functional in aetiology. Few studies have reported the manometric data of normal and constipated children.AimTo evaluate the manometric parameters in children with functional constipation and to assess any possible changes in these parameters after treatment.Material and methodsA prospective descriptive study was conducted at a single centre, enrolling 50 children diagnosed with functional constipation based on Rome IV criteria. Their age ranged from 6 to 14 years with a mean of 7.31 ±1.72 years. High-resolution manometry was performed on all children at the initial presentation and after six months of treatment.ResultsThe studied children showed markedly abnormal rectal sensation parameters (increased first sensation, first urge, intense urge, and maximum tolerable volume) during rectal balloon distension. These parameters were even higher in children with stool incontinence (p = 0.005). Manometric data after 6 months of treatment showed that the resting and squeeze pressures were increased when compared to pre-treatment recordings; however, both were statistically insignificant (p = 0.474 and p = 0.155, respectively). Abnormalities in rectal sensations and the manometric parameters reached near normal values following treatment.ConclusionsAnorectal manometry is sensitive in predicting improvement in patient condition even before complete clinical cure, and it has a prognostic role in the management of childhood constipation. More research is still needed before recommending anorectal manometry as a routine diagnostic or prognostic tool in paediatric constipation management.

Magnetic resonance imaging analysis of brain function in patients with irritable bowel syndrome

BackgroundIrritable bowel syndrome (IBS) is a common functional disease of the gastrointestinal tract. The current study aimed to examine the association between visceral hypersensitivity in IBS and cortical activation using functional magnetic resonance imaging (fMRI), and to elucidate the role of psychological factors in the pathogenesis of IBS.MethodsThe present study included 31 patients with IBS and 20 healthy controls. Cerebral function was assessed using fMRI. During imaging, a Sengstaken-Blakemore tube was placed within the rectum approximately 10 cm from the anus, following which gas was rapidly injected into the airbag using a 150-ml syringe. Images were obtained at 40 ml, 80 ml, and 120 ml of expansion. Psychological status was evaluated using the Hospital Anxiety and Depression Scale (HADS).ResultsAnxiety and depression scores were higher among patients with IBSthan among controls (both P < 0.05), although scores in both groups were below the level of clinical diagnosis. Brain activation in regions of interest (parietal areas, prefrontal cortex, cerebellum, anterior cingulate cortex, insular cortex, and thalamus) increased along with increases in rectal balloon dilation, except in women with IBS and patients with disease duration less than 5 years. Furthermore, region of interest (ROI) activation (such as the parietal region, prefrontal cortex, cerebellum, anterior cingulate cortex, insular cortex, and thalamus) differed significantly between the 40-ml and 120-ml conditions, and between the 80-ml and 120-ml conditions (P < 0.05), among patients with IBS with anxiety or depression scores less than 9 points.ConclusionsOverall, our findings indicate that changes in brain activation due to changes in rectal balloon distension can be objectively and accurately measured using fMRI. Although our results indicated that visceral hypersensitivity during IBS is associated with changes in cortical activation, further studies utilizing larger sample sizes are required to more fully elucidate the association between psychological factors and visceral hypersensitivity in IBS.