Visceral hypersensitivity

Visceral hypersensitivity is considered one of the causes of functional gastrointestinal disorders. The objectives of this review are to provide a practical description of neuroanatomy and physiology of gut sensation, to describe the diverse tests of visceral sensation and the potential role of brain imaging to further our understanding of visceral sensitivity in health and disease. Changes in motor function in the gut may influence sensory levels, eg, during contractions or as a result of changes in viscus compliance. New insights on sensory end organs, such as intraganglionic laminar endings, and basic neurophysiologic studies showing afferent firing during changes in stretch rather than tension illustrate the importance of different types of stimuli, not just tension, to stimulate afferent sensation. These insights provide the basis for understanding visceral sensation in health and disease, which will be extensively discussed in subsequent articles.

Impaired reflex control of intestinal gas transit in patients with abdominal bloating

BACKGROUND

Patients with abdominal bloating and distension exhibit impaired transit of intestinal gas which may lead to excessive gas retention and symptoms. Furthermore, we have previously shown that intestinal gas transit is normally accelerated by rectal distension. We hypothesise that in patients with functional bloating this modulatory mechanism fails and impairs gas transit.

METHODS

In 12 healthy subjects and eight patients with abdominal bloating we compared, by paired studies, the effect of rectal versus sham distension on intestinal gas transit. Gas was infused into the jejunum (12 ml/min) for three hours with simultaneous perfusion of lipids into the duodenum (Intralipid 1 kcal/min) while measuring evacuation of gas per rectum.

RESULTS

In healthy subjects, duodenal lipid infusion produced gas retention (409 (68) ml) which was prevented by rectal distension (90 (90) ml; p<0.05 v sham distension). In contrast, rectal distension in patients with abdominal bloating failed to reduce lipid induced gas retention (771 (217) ml retention during rectal distension v 730 (183) ml during sham distension; NS; p<0.05 v healthy controls for both).

CONCLUSION

Failure of distension related reflexes impairs intestinal gas propulsion and clearance in patients with abdominal bloating.

Chronic abdominal pain in children

Children and adolescents with chronic abdominal pain pose unique challenges to their caregivers. Affected children and their families experience distress and anxiety that can interfere with their ability to perform regular daily activities. Although chronic abdominal pain in children is usually attributable to a functional disorder rather than organic disease, numerous misconceptions, insufficient knowledge among health care professionals, and inadequate application of knowledge may contribute to a lack of effective management. This clinical report accompanies a technical report (see page e370 in this issue) on childhood chronic abdominal pain and provides guidance for the clinician in the evaluation and treatment of children with chronic abdominal pain. The recommendations are based on the evidence reviewed in the technical report and on consensus achieved among subcommittee members.

Probiotics and functional abdominal bloating

Functional abdominal bloating is a condition dominated by a feeling of abdominal fullness or bloating and without sufficient criteria for another functional gastrointestinal disorder. The currently used therapeutic approaches aim to reduce the volume of intestinal gas, thus increasing intestinal gas elimination or reducing its production. Some promising results have been obtained by the use of prokinetics, such as tegaserod and Prostigmine, and by the use of nonabsorbable antibiotics, such as rifaximin. Another therapeutic approach is represented by the administration of probiotics to modify the composition of colonic flora and thus the production of intestinal gas. The authors recently studied the effect of LGG, which proved to be more effective than placebo in reducing the severity of symptoms.

Effect of a corticotropin releasing hormone receptor antagonist on colonic sensory and motor function in patients with irritable bowel syndrome

BACKGROUND AND AIMS

Corticotropin releasing hormone (CRH) is a major mediator of the stress response in the brain-gut axis. Irritable bowel syndrome (IBS) is presumed to be a disorder of the brain-gut link associated with an exaggerated response to stress. We hypothesised that peripheral administration of alpha-helical CRH (alphahCRH), a non-selective CRH receptor antagonist, would improve gastrointestinal motility, visceral perception, and negative mood in response to gut stimulation in IBS patients.

METHODS

Ten normal healthy subjects and 10 IBS patients, diagnosed according to the Rome II criteria, were studied. The tone of the descending colon and intraluminal pressure of the sigmoid colon were measured at baseline, during rectal electrical stimulation (ES), and at recovery after administration of saline. Visceral perception after colonic distension or rectal ES was evaluated as threshold values on an ordinate scale. The same measurements were repeated after administration of alphahCRH (10 micro g/kg).

RESULTS

ES induced significantly higher motility indices of the colon in IBS patients compared with controls. This response was significantly suppressed in IBS patients but not in controls after administration of alphahCRH. Administration of alphahCRH induced a significant increase in the barostat bag volume of controls but not in that of IBS patients. alphahCRH significantly reduced the ordinate scale of abdominal pain and anxiety evoked by ES in IBS patients. Plasma adrenocorticotropic hormone and serum cortisol levels were generally not suppressed by alphahCRH.

CONCLUSION

Peripheral administration of alphahCRH improves gastrointestinal motility, visceral perception, and negative mood in response to gut stimulation, without affecting the hypothalamo-pituitary-adrenal axis in IBS patients.

Abnormal predefecatory colonic motor patterns define constipation in obstructed defecation

BACKGROUND & AIMS

The pathophysiology of constipation in the syndrome of obstructed defecation is unknown. Using 24-hour pancolonic manometric recordings of the unprepared colon to record basal pressures and spontaneous defecation episodes, we tested the hypothesis that the frequency, timing, or spatial distribution of propagating colonic pressure waves is abnormal in patients with obstructed defecation.

METHODS

In 11 patients with obstructed defecation and 16 healthy controls, pressures were recorded using a nasocolonic catheter that was positioned such that 16 recording sites spanned the unprepared colon at 7.5-cm intervals.

RESULTS

The overall frequency of propagating sequences (PS) in the colon did not differ between patients and controls. When compared with controls, patients had a significant increase in the frequency of retrograde and antegrade PS (P < 0.05) in the left colon and a significant reduction in the amplitude of propagating pressure waves throughout the entire colon (P < 0.03). Defecation occurred in 6 of 11 patients and 9 of 16 controls. In the 15 minutes before defecation, controls showed a highly significant increase in frequency (P = 0.001) and amplitude (P = 0.01) of PS. In contrast, patients did not demonstrate this or the typical spatiotemporal organization of PS normally observed before expulsion of stool.

CONCLUSIONS

Patients with obstructed defecation lack the normal predefecatory augmentation in frequency and amplitude of propagating pressure waves and lack the normal stereotypic spatiotemporal patterning of colonic pressure waves that would normally culminate in effective expulsion of stool.

Colonic regular contractile frequency patterns in irritable bowel syndrome: the 'spastic colon' revisited

BACKGROUND

Irritable bowel syndrome is a frequent gastrointestinal disorder of which the pathophysiological basis is still not completely understood. Among the various proposed mechanisms, colonic motility may play a role, at least in a subset of patients.

AIMS

To investigate the regular colonic contractile patterns in patients with irritable bowel syndrome. Our working hypothesis was that an increase of these patterns in such condition might represent a motility equivalent of the so-called 'spastic colon'.

PATIENTS AND METHODS

Twelve patients of both genders were investigated by means of 24 h colonic manometry, and the results were compared to those from 20 healthy controls. Regular contractile patterns (with frequencies ranging from 2 to 8 per min) were calculated for the entire recording period and in single colonic segments.

RESULTS

Overall, colonic frequency patterns were significantly more frequent in patients than controls (12.6% vs 6.4% of the total contractile activity, P < 0.001); in both groups, the 3 cycles/min frequency was predominant, especially in the sigmoid colon. More than 40% patients displayed a correlation between abdominal pain and occurrence of regular contractile frequencies.

CONCLUSIONS

Abnormal colonic motility may play some role in the pathogenesis of symptoms related to irritable bowel syndrome, with an excess of regular contractile activity related to the so-called 'spastic colon'.

Effects of mu and kappa opioid receptor agonists and antagonists on contraction of isolated colon strips of rats with cathartic colon

AIM: To study the effects of mu and kappa opioid receptor agonists and antagonists on the isolated colon strips of rats with cathartic colon.

METHODS: Cathartic colon model was established by feeding rats with contact laxatives, and effects of mu and kappa opioid receptor agonists and antagonists on electricity-stimulated contraction of isolated colon strips of rats with cathartic colon were observed.

RESULTS: Compared with control group, exogenous mu and kappa agonists inhibited significantly electricity-stimulated contraction of strips of cathartic colon (8.50 ± 0.89 mm, 6.24 ± 0.91 mm, 3.35 ± 0.6 mm vs 11.40 ± 0.21 mm P < 0.01; 8.98 ± 0.69 mm, 6.89 ± 0.71 mm, 4.43 ± 0.99 mm vs 11.40 ± 0.21 mm, P < 0.01). In contrast, the exogenous mu antagonist significantly enhanced electricity-stimulated contraction of isolated colon strips (13.18 ± 0.93 mm, 15.87 ± 0.98 mm, 19.46 ± 1.79 mm vs 11.40 ± 0.21 mm, P < 0.01), but kappa antagonist had no effect on the isolated colon strips of rats with cathartic colon.

CONCLUSION: Mu and kappa opioid receptors are involved in the regulation of colon motility of rats with cathartic colon.

[Bloating: the importance of gas]

Blähungen sind vor allem bei funktionellen Darmkrankheiten ein häufiges Problem. Erstaunlicherweise spielt hier das Luftvolumen im Darm nicht die bedeutende Rolle, wie allgemein vermutet wird. Im folgenden Artikel wird aufgezeigt, dass das Gefühl von Blähungen hauptsächlich durch eine gestörte segmentale Gas-Propulsion und -Retention hervorgerufen wird zusammen mit einer viszeralen Hypersensitivität.

Colonic transit time and constipation in children with spastic cerebral palsy

OBJECTIVES

To evaluate colonic motility and to investigate contributing factors to colonic dysmotility in children with spastic cerebral palsy (CP).

DESIGN

Cross-sectional study.

SETTING

A university-based rehabilitation hospital.

PARTICIPANTS

Thirty-eight children with spastic CP.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Colonic transit time was measured by using a Sitzmarks. The nutrient intake during 3 consecutive days was analyzed by using the ESHA Food Processor program.

RESULTS

A significant relationship between colon transit time and stool frequency was observed (P<.05). All children with constipation and 17 (60.8%) of 28 without constipation showed an abnormal segmental colon transit time in at least 1 segment of the colon. A transit time delay at the proximal segment of colon was remarkable in CP children with constipation. In children without constipation, a transit time delay was marked at the rectosigmoid colon only. Constipation and transit time delay were significantly related to ambulatory function (P<.05).

CONCLUSIONS

A transit time delay at total or segmental colon was frequently observed in children with CP. Constipation and colonic motility were related to ambulatory function.

The contributions of suggestion, desire, and expectation to placebo effects in irritable bowel syndrome patients. An empirical investigation

In order to investigate external factors that may influence the magnitude of placebo analgesia as well as psychological factors that mediate placebo analgesia, 13 irritable bowl syndrome (IBS) patients rated evoked rectal distension and cutaneous heat pain under the conditions of natural history (NH), rectal placebo (RP), rectal nocebo (RN), rectal lidocaine (RL) and oral lidocaine (OL). Patients were given verbal suggestions for pain relief and rated expected pain levels and desire for pain relief for both evoked visceral and cutaneous pain, respectively. Large reductions in pain intensity and pain unpleasantness ratings were found in the RP, RL and OL condition as compared to the natural history condition, whereas no significant difference in pain reduction between the three treatment conditions was found. Ratings during RN and NH were not statistically different. Compared to a previous study, which shows that rectal lidocaine reverses visceral and cutaneous hyperalgesia, these results suggest that adding a verbal suggestion for pain relief can increase the magnitude of placebo analgesia to that of an active agent. Since IBS patients rate these stimuli as much higher than do normal control subjects and since placebo effects were very large, they probably reflect anti-hyperalgesic mechanisms to a major extent. Expected pain levels and desire for pain relief accounted for large amounts of the variance in visceral pain intensity in the RP, RL, and OL condition (up to 81%), and for lower amounts of the variance in cutaneous pain intensity. Hence, the combination of expected pain levels and desire for pain relief may offer an alternative means of assessing the contribution of placebo factors during analgesia.

Tegaserod: a review of its use in the management of irritable bowel syndrome with constipation in women

The treatment of irritable bowel syndrome with constipation (IBS-C) has historically been based on the severity of symptoms, with education, reassurance, dietary advice, bulking agents and laxative therapy offered as appropriate. Tegaserod (Zelnorm, Zelmac) is the first selective serotonin 5-HT(4) receptor partial agonist to be approved for the treatment of this syndrome. Tegaserod is active against multiple irritable bowel syndrome (IBS) symptoms; it stimulates gut motility and reduces visceral sensitivity and pain. The drug does not cure IBS and was not designed to treat the diarrhoea-predominant version. Its efficacy in men has not been established. Three large well designed clinical trials of tegaserod 6 mg twice daily for 12 weeks in patients (mainly women) with IBS-C have demonstrated superiority versus placebo in global relief from symptoms. Global relief response rates were 38.4-46.8% with tegaserod 6 mg twice daily and 28.3-38.8% with placebo (p < 0.05-0.0001 vs placebo). The relative increases in response rates with tegaserod 6 mg twice daily over the already high responses in the placebo groups ranged from 12-65% after 4-12 weeks of treatment. A response was seen within the first week. The proportion of patients with satisfactory relief from symptoms fell over the 4-week period following withdrawal of tegaserod and placebo, but did not reach baseline levels during this time. Diarrhoea has been associated with tegaserod in clinical trials (an incidence of about 10% versus 5% with placebo, usually occurring in the first week of treatment), but the drug is otherwise well tolerated. There were no apparent changes in the tolerability profile with extended tegaserod treatment (</=12 months). In conclusion, oral tegaserod 6 mg twice daily for 12 weeks is effective and well tolerated in the treatment of IBS-C in women. Data on long term and comparative efficacy, cost-effectiveness and quality-of-life effects would be beneficial; however, in light of the fact that very few alternatives for the treatment of IBS-C have proven efficacy, tegaserod appears to be a promising option in women not responding to increased dietary fibre or osmotic laxative therapy.

Current concepts of the irritable bowel syndrome

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

Regional brain activation in response to rectal distension in patients with irritable bowel syndrome and the effect of a history of abuse

Previous studies have demonstrated alterations in brain response to rectal distension in patients with irritable bowel syndrome (IBS) compared to controls. Our aim was to compare regional brain activity in response to rectal balloon distension in patients with IBS and healthy controls. We studied six patients with IBS and six healthy controls. Positron emission tomography scans were obtained during rectal balloon distensions. Statistical parametric mapping and region of interest analysis were performed to identify and compare differences in regional cerebral blood flow (CBF) for each distension pressure within and between the groups of interest. In post-hoc analyses, patients with a history of sexual or physical abuse were compared to patients without abuse. In response to rectal distension, controls exhibit a greater increase in anterior cingulate cortex (ACC) activity compared to the IBS group (Z = 3.2, P = 0.001). Thalamic activity was higher in the IBS patients relative to the control group (Z = 3.3, P < 0.001). Increased ACC activity was observed in IBS patients with no history of abuse (Z = 5.2, P < 0.001) similar to controls, whereas no such increased activity was noticed in the abused group. In conclusion, this study replicates previous findings showing alterations in brain response to rectal distension in patients with IBS. The observations on the effect of abuse suggest a possible modulating role of abuse history on this brain response.

Gastrointestinal dysfunction in a community sample of subjects with symptoms of irritable bowel syndrome

BACKGROUND/AIM

Irritable bowel syndrome (IBS) affects about 15-20% of the population of the Western countries. Traditionally, IBS has been an exclusion diagnosis, but recently definitions have emerged from population-based research. The aim of this population-based study was to evaluate any association between gastrointestinal pathophysiology and IBS in subjects with symptoms of IBS compared to subjects with no abdominal complaints.

METHODS

From a random sample of 2,656 participants, subjects with IBS (32) together with subjects without abdominal complaints (26), were invited for further evaluation. IBS was defined as more than weekly experience of abdominal pain and distension, and in addition either borborygmia or altering stool consistency. The diagnostic work-up consisted of gastroscopy, manometry and 23-hour pH and pressure recordings of the oesophagus, lactose tolerance test, barium enema, measurement of colonic transit time, and rectoscopy.

RESULTS

Compared to the group without abdominal complaints significantly more subjects with IBS had spasms of the colon (OR = 10.2 (1.2-87.3)), and abnormal contractions of the oesophagus at manometry (OR = 9.1 (1.1-78.2)). Furthermore, there was a non-significant tendency towards spasms at 23-hour pH and pressure recordings (OR = 3.58 (0.4-35.2)), and more discomfort at lactose tolerance test (OR = 5.8 (0.6-51.3)) in persons with IBS compared to subjects without abdominal complaints.

CONCLUSION

The results of this population-based study indicate that signs of gastrointestinal dysmotility and hyperperception are more prevalent in subjects with IBS than in subjects without abdominal complaints.

Serotonin and its implication for the management of irritable bowel syndrome

Our understanding of the enteric nervous system (ENS) has evolved from the "classical" view, in which the brain controls all enteric behavior, to the current view, which holds that enteric innervation is one of local control within the bowel, modified by a bidirectional "dialogue" with the brain. The ENS independently controls enteric reflexes through intrinsic primary afferent neurons, which monitor intraluminal conditions. This monitoring is accomplished through the use of enteroendocrine cells in the mucosa, the best known of which are the serotonin-containing enterochromaffin cells. This article describes the roles that serotonin, specific serotonin-receptor subtypes, and the serotonin reuptake transporter play in the ENS and in the communication between the ENS and central nervous system. The way in which these findings have implicated serotonin in irritable bowel syndrome is discussed.

Tegaserod and other serotonergic agents: what is the evidence?

Through effects on gastrointestinal motor and secretory function as well as visceral sensation, serotonin (5-HT) plays a key role in the pathogenesis of irritable bowel syndrome (IBS). In particular, 5-HT3 and 5-HT4 receptors appear to be very important in IBS. This article critically appraises the evidence supporting the use of the 5-HT3 receptor antagonist alosetron in the treatment of women with diarrhea-predominant IBS. The safety profile and restricted-use program for alosetron is also reviewed. This discussion is followed by a comprehensive review of the efficacy and safety data in support of tegaserod for women with constipation-predominant IBS.

New approaches to the medical treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder with a worldwide distribution; it is characterized by abdominal pain and discomfort associated with an alteration of bowel function. The treatment approach for IBS depends on the patient's presenting symptoms at the time of diagnosis, and treatment is usually directed toward the predominant symptom. In this review we discuss the current approach to the treatment of IBS.

New insights into the psychosocial aspects of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common condition varying in severity from trivial to incapacitating. The more severe cases are associated with poor quality of life, absenteeism from work, frequent consultation with medical professionals, and psychosocial distress. Historically the disorder was often considered as purely psychosomatic in origin, but we now know that this is a gross oversimplification. Gastrointestinal disorders are better understood using the biopsychosocial model, which emphasizes the importance of biologic and psychosocial factors. This article reviews the epidemiologic association of IBS with psychological and social stresses and explores how such stresses may influence consulting behavior and outcome. This review also describes physiologic mechanisms that may be involved in IBS and discusses the role of psychological therapies and psychotropic medication in the treatment of this condition.

Current insights into the pathophysiology of irritable bowel syndrome

Recent reports have emphasized the possible role of mucosal immune activation and inflammation in neuropathic changes in the pathophysiology of irritable bowel syndrome (IBS). However, novel findings using functional brain imaging techniques have underlined the importance of altered perception of visceral stimuli to symptom generation in IBS. These new developments have rekindled an old debate on peripheral versus central mechanisms in the pathophysiology of IBS. In this review we discuss the latest findings in light of these two concepts. In addition, we provide evidence for the hypothesis that, in the absence of alterations in endogenous pain modulation systems and changes in visceral perception, chronic inflammatory mucosal changes in the gut are not a plausible mechanism to explain the presence of chronic abdominal pain, a cardinal IBS symptom.

Association between pain episodes and high amplitude propagated pressure waves in patients with irritable bowel syndrome

OBJECTIVES

In the pathogenesis of irritable bowel syndrome (IBS), both increased visceral sensitivity and altered colonic motility seem to play a role. The aim of this study was to quantify the temporal relationship between pain episodes and the occurrence of high amplitude propagated pressure waves (HAPPWs).

METHODS

A total of 11 IBS patients with the nonconstipation predominant pattern of IBS and 10 sex- and age-matched healthy volunteers were studied. On day 1, a solid state manometric catheter was positioned in the left colon and connected to a data logger. The subjects then went home. Thereafter they pressed a button on the data logger at the beginning and end of each pain episode. The 24-h manometric signal recorded on day 2 was divided into consecutive 5-min periods. These periods were evaluated for the occurrence of pain and HAPPWs. Fisher's exact test was applied to calculate the probability that HAPPWs and pain episodes were unrelated. The symptom association probability (SAP) was calculated as (1.0 - P) x 100%. A SAP of >95% was considered to indicate that the observed association did not occur by chance.

RESULTS

In four of seven patients with pain on day 2, the SAP was >95%. HAPPWs that were related to pain originated at a more proximal level (p = 0.026) and occurred earlier (p = 0.007) than HAPPWs that were not related to pain. The duration of a pain period was correlated with the number of pain-related HAPPWs in that period (r = 0.906, p = 0.013). Two of the 10 healthy subjects experienced pain, and these pain episodes were not associated with HAPPWs.

CONCLUSIONS

Using objective analysis techniques, an association between pain episodes and HAPPWs was found in nonconstipated IBS patients with pain. HAPPWs that are associated with pain are only slightly different from HAPPWs not associated with pain.

Impact of sex and gender on irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional bowel disorder characterized by abdominal pain and change in defecation pattern. This review addresses the topic of possible sex (genetic, biological) and gender (experiential, perceptual) differences in individuals with and without IBS. Several observations make the topic important. First, there is a predominance of women as compared to men who seek health care services for IBS in the United States and other industrialized societies. Second, menstrual cycle-linked differences are observed in IBS symptom reports. Third, women with IBS tend to report greater problems with constipation and nongastrointestinal complaints associated with IBS. Fourth, serotonin (5-HT3) receptor antagonist and 5-HT4 partial agonist drugs appear to more effectively diminish reports of bowel pattern disruption in women with IBS as compared to men. This review examines sex and gender modulation of gastrointestinal motility and transit, visceral pain sensitivity, autonomic nervous system function, serotonin biochemistry, and differences in health care-seeking behavior for IBS.

Functional brain imaging in irritable bowel syndrome with rectal balloon-distention by using fMRI

AIM: Irritable bowel syndrome (IBS) is characterized by abdominal pain and changes in stool habits. Visceral hypersensitivity is a key factor in the pathophysiology of IBS. The aim of this study was to examine the effect of rectal balloon-distention stimulus by blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) in visceral pain center and to compare the distribution, extent, and intensity of activated areas between IBS patients and normal controls.

METHODS: Twenty-six patients with IBS and eleven normal controls were tested for rectal sensation, and the subjective pain intensity at 90 mL and 120 mL rectal balloon-distention was reported by using Visual Analogue Scale. Then, BOLD-fMRI was performed at 30 mL, 60 mL, 90 mL, and 120 mL rectal balloon-distention in all subjects.

RESULTS: Rectal distention stimulation increased the activity of anterior cingulate cortex (35/37), insular cortex (37/37), prefrontal cortex (37/37), and thalamus (35/37) in most cases. At 120 mL of rectal balloon-distention, the activation area and percentage change in MR signal intensity of the regions of interest (ROI) at IC, PFC, and THAL were significantly greater in patients with IBS than that in controls. Score of pain sensation at 90 mL and 120 mL rectal balloon-distention was significantly higher in patients with IBS than that in controls.

CONCLUSION: Using fMRI, some patients with IBS can be detected having visceral hypersensitivity in response to painful rectal balloon-distention. fMRI is an objective brain imaging technique to measure the change in regional cerebral activation more precisely. In this study, IC and PFC of the IBS patients were the major loci of the CNS processing of visceral perception.