Alterations in cerebral potentials evoked by rectal distention and drinking ice water in patients with irritable bowel syndrome

AIM: Visceral hypersensitivity has been found to be present in irritable bowel syndrome (IBS). The current study sought to study visceral afferent hypersensitivity in IBS patients and obtain further objective evidence of alterations in intestinal afferent pathways in IBS patients by cerebral evoked potentials (CEP). METHOD: We studied 30 female IBS patients and 12 female healthy subjects. Rectal perception thresholds to balloon distention were measured and CEP was recorded in response to rhythmic rectal distention (two distention series, each of 100 repetitions at a frequency of 1 Hz) at the volume of perception thresholds. All subjects were then asked to drink 220 mL 4 degrees C ice water and the above steps were repeated 20 min later. RESULTS: Rectal distention led to recognizable and reproducible CEP. Compared to healthy subjects, IBS patients demonstrated significantly shorter N1, P1 and N2 latencies (P < 0.05). After drinking ice water, IBS patients exhibited further shortened N1, P1 and N2 latencies (P < 0.05), but drinking did not alter the latencies of healthy controls and the amplitudes of both IBS patients and healthy controls. CONCLUSION: The shorter latency of cerebral potentials evoked by rectal distention and ice water stimulation in IBS patients provided further objective evidence for defective visceral afferent transmission in IBS patients.     

Repetitive rectal painful distention induces rectal hypersensitivity in patients with irritable bowel syndrome

Background A reduced rectal perceptual threshold has been reported in patients with irritable bowel syndrome (IBS), but this phenomenon may be induced by a comorbid psychological state. We evaluated the rectal pain threshold at baseline and after conditioning (repetitive rectal painful distention: RRD) in patients with IBS or functional abdominal pain syndrome (FAPS), which is an abdominal pain disorder, and in healthy controls, and determined whether rectal hypersensitivity is a reliable marker for IBS. Methods The rectal sensory threshold was assessed by a barostat. First, a ramp distention of 40 ml/min was induced, and the threshold of pain and the maximum tolerable pressure (mmHg) were measured. Next, RRD (phasic distentions of 60-s duration separated by 30-s intervals) was given with a tracking method until the subjects had complained of pain six times. Finally, ramp distention was induced again, and the same parameters were measured. The normal value was defined by calculating the 95% confidence intervals of controls. Results Five or six of the seven IBS patients showed a reduced rectal pain threshold or maximum tolerable pressure, respectively, at baseline. In all patients with IBS, both thresholds were reduced after RRD load, but they were reduced in none of the patients with FAPS. RRD significantly reduced both thresholds in the IBS group (P < 0.05), but it had no effect in the control or FAPS groups. Conclusions Rectal hypersensitivity induced by RRD may be a reliable marker for IBS. Conditioning-induced visceral hypersensitivity may play a pathophysiologic role in IBS.     

Rectal distention testing in patients with irritable bowel syndrome: sensitivity,specificity, and predictive values of pain sensory thresholds

BACKGROUND & AIMS: Visceral hypersensitivity was detected in patients with functional gastrointestinal disorders and has been proposed as a biological marker of irritable bowel syndrome (IBS). The purpose of this study was to assess the sensitivity, specificity, and the predictive values of pain thresholds evaluated by rectal distention using an electronic barostat in patients with or without IBS and in control subjects. METHODS: Patients were diagnosed according to Rome II criteria. Rectal sensory thresholds were determined in 164 patients (86 IBS patients, 26 painless constipation, 21 functional dyspepsia, and 31 miscellaneous conditions) and in 25 normal controls. All subjects underwent a series of rectal isobaric distentions using an electronic barostat. The bag was progressively distended from 0 to 48 mm Hg and, in response to distention, subjects reported on discomfort or pain. RESULTS: Pain thresholds were lower in IBS patients (30.4 +/- 6.7 mm Hg) compared with controls (44.5 +/- 5), painless constipated (45.4 +/- 5.3), functional dyspepsia (39.4 +/- 7.8), and miscellaneous patients (43.2 +/- 5.5). At the level of 40 mm Hg, the sensitivity of the rectal barostat to identify IBS patients from normal subjects and non-IBS patients was 95.5% and its specificity was 71.8%. The positive predictive value was 85.4%. The negative predictive value was 90.2%. CONCLUSIONS: Lowered rectal pain threshold is a hallmark of IBS patients. Rectal barostat testing is useful to confirm the diagnosis of IBS and to discriminate IBS from other causes of abdominal pain.     

Irritable bowel syndrome patients show enhanced modulation of visceral perception by auditory stress

OBJECTIVES: Symptoms in irritable bowel syndrome (IBS) patients are sensitive to psychological stressors. These effects may operate through an enhanced responsiveness of the emotional motor system, a network of brain circuits that modulate arousal, viscerosomatic perception, and autonomic responses associated with emotional responses, including anxiety and anger. The aim of this study was to test the primary hypothesis that IBS patients show altered perceptual responses to rectal balloon distention during experimentally induced psychological stress compared with healthy control subjects. METHODS: A total of 15 IBS patients (nine women and six men) and 14 healthy controls (seven women and seven men) were studied during two laboratory sessions: 1) a mild stress condition (dichotomous listening to two conflicting types of music), and 2) a control condition (relaxing nature sounds). The stress and relaxation auditory stimuli were delivered over a 10-min listening period preceding rectal distentions and during the rectal distentions but not during the distention rating process. Ratings of intensity and unpleasantness of the visceral sensations, subjective emotional responses, heart rate, and neuroendocrine measures (norepinephrine, cortisol, adrenocorticotropic hormone [ACTH], and prolactin) were obtained during the study. RESULTS: IBS patients, but not healthy controls, rated the 45-mm Hg visceral stimulus significantly higher in terms of intensity and unpleasantness during the stress condition compared with the relaxation condition. IBS patients also reported higher ratings of stress, anger, and anxiety during the stress compared with the relaxing condition, whereas controls had smaller and nonsignificant subjective responses. Heart rate measurements, but not other neuroendocrine stress measures, were increased under the stress condition in both groups. CONCLUSION: These findings confirm the hypothesis of altered stress-induced modulation of visceral perception in IBS patients.     

Corticotropin-releasing factor induces rectal hypersensitivity after repetitive painful rectal distention in healthy humans

Background Rectal hypersensitivity induced by repetitive rectal distention (RRD) is reported to be a response specific to patients with irritable bowel syndrome (IBS), and is not observed in healthy controls. We evaluated the rectal pain threshold (PT) and determined whether intravenous corticotropin-releasing factor (CRF) induces rectal hypersensitivity after RRD in healthy humans, that is, whether it mimics the response observed in IBS patients. Methods A double-blind placebo-controlled study design (CRF or vehicle) was used. In the first experiment, PT (mmHg) induced by ramp distention was measured by a barostat. Then CRF (100 μg, n = 5) or vehicle (n = 6) was injected intravenously (iv) followed by RRD, consisting of phasic distentions with sensory tracking, which lasted until the subjects had complained of pain six times. After RRD, PT was measured again. In another experiment, PT was measured, and then CRF (n = 5) or vehicle (n = 5) was injected iv. After 45 min, ramp distention was again induced to determine PT. Results In the placebo group, PT was not modified by RRD (before RRD, 33.0 ± 6.8; after RRD, 33.4 ± 4.5), while it was significantly reduced in the CRF-treated group (before RRD, 32.9 ± 9.0; after RRD, 26.1 ± 7.9, P < 0.05). On the other hand, CRF or vehicle without RRD did not alter PT (before iv-CRF, 35.2 ± 4.2; after iv-CRF, 35.3 ± 4.9; before iv-vehicle, 34.5 ± 7; after iv-vehicle, 35.5 ± 6.8). Conclusions These results indicate that CRF modifies rectal sensation in healthy humans and mimics an IBS-specific visceral response, suggesting the possible contribution of CRF to the pathogenesis of IBS.     

Sensory and motor responses to rectal distention vary according to rate and pattern of balloon inflation

Anorectal motor activity and rectal sensation were recorded in 12 normal male subjects during ramp distention of the rectum with water and air at randomized rates of 10, 20, 50, and 100 mL/min and during intermittent rapid distention with air. There were no significant differences between the results of ramp inflation with water or with air, and the repeated infusion of the same medium yielded reproducible results. Ramp distention induced sigmoid pressure-volume profiles. Different sensations occurred at specific points on the pressure-volume curve and were maintained until succeeded by the next sensation. Initial perception of the distention occurred during the initial steep pressure increase, the sensation of wind occurred during the plateau phase, and the desire to defecate occurred at the onset of the final rapid ascent. Rectal sensations were induced at lower volumes at low infusion rates when the slope of the pressure-volume relationship was shallower than at high infusion rates. This suggests that the receptor triggering rectal sensation is not a simple volume or pressure receptor, but is more likely to be a slowly adapting mechanoreceptor lying parallel to the circular muscle of the rectal wall. During rapid intermittent distention, the rectal volumes required to elicit rectal sensations were lower than during ramp distention, although the pressure-volume curve was steeper. Moreover, sensations often only lasted a short period of time but recurred on deflation. These data suggest activation of an additional population of rapidly adapting or high threshold mechanoreceptors. Anal relaxation was always evoked by intermittent rectal distention and was almost always associated with a rectal sensation and an increase in external anal sphincter activity. In contrast, anal relaxation could be absent or delayed during ramp inflation, especially at lower infusion rates, suggesting that internal sphincter can maintain continence for a long period of time while the rectum is slowly filling. Rectal sensation and concomitant external anal sphincter activity was not associated with anal relaxation during ramp inflation; most subjects felt the sensation long after the pressure reached its lowest level. However, under all circumstances the onset of rectal sensation was associated with an increase of external anal sphincter electrical activity. In conclusion, the rectal sensory and anorectal motor responses to distention depend on the rate and pattern of distention, which may activate a different population of receptors. Results from different laboratories cannot be compared directly unless the pattern and rate of distension are the same.     

Condition-specific deactivation of brain regions by 5-HT3 receptor antagonist Alosetron

BACKGROUND & AIMS: The 5-HT3 receptor (5-HT3R) antagonist Alosetron (Alos) reduces the symptoms of female patients with diarrhea-predominant irritable bowel syndrome (IBS); yet, the mechanism(s) underlying this effect remains incompletely understood. We determined the effect of Alos on regional cerebral blood flow (rCBF) in the absence and presence of rectal or sigmoid stimulation to evaluate 2 hypothesized mechanisms of therapeutic action: peripheral antinociception and inhibition of emotional motor system (EMS) regions in the brain. METHODS: Forty-nine nonconstipated irritable bowel syndrome (IBS) patients (26 female) received H(2)(15)O positron emission tomography (PET) brain scans before a randomized, placebo-controlled, 3-week trial with Alos (1-4 mg twice daily). PET scans were repeated after treatment in 37 completers. We assessed rCBF during baseline, rectal distention, and anticipation of undelivered rectal distention. The 3 conditions were repeated after a series of noxious sigmoid distentions. Rectal (45 mm Hg) and sigmoid (60 mm Hg) distentions were performed with a computer-controlled barostat device. RESULTS: Alos treatment, as compared with placebo, improved IBS symptoms and reduced rCBF in 5-HT3R containing regions of the EMS, but not in areas activated by pain. Reduction of rCBF appeared greatest in the absence of visceral stimulation, and was partially reversed by rectal or sigmoid distention. Symptom improvement across sessions was significantly correlated with rCBF decreases in the 5-HT3R-rich amygdala, ventral striatum, and dorsal pons. CONCLUSIONS: Reduction in IBS symptoms correlated with a drug-induced reduction in the activity of central autonomic networks mediating emotional expression that was maximal in the absence of nociceptive input.     

Regional cerebral activation in irritable bowel syndrome and control subjects with painful and nonpainful rectal distention

BACKGROUND & AIMS: Irritable bowel syndrome (IBS) is characterized by visceral hypersensitivity, possibly related to abnormal brain-gut communication. Positron emission tomography imaging has suggested specific central nervous system (CNS) abnormalities in visceral pain processing in IBS. This study aimed to determine (1) if functional magnetic resonance imaging (fMRI) detects CNS activity during painful and nonpainful visceral stimulation; and (2) if CNS pain centers in IBS respond abnormally. METHODS: fMRI was performed during nonpainful and painful rectal distention in 18 patients with IBS and 16 controls. RESULTS: Rectal stimulation increased the activity of anterior cingulate (33/34), prefrontal (32/34), insular cortices (33/34), and thalamus (32/34) in most subjects. In IBS subjects, but not controls, pain led to greater activation of the anterior cingulate cortex (ACC) than did nonpainful stimuli. IBS patients had a greater number of pixels activated in the ACC and reported greater intensity of pain at 55-mm Hg distention than controls. CONCLUSIONS: IBS patients activate the ACC, a critical CNS pain center, to a greater extent than controls in response to a painful rectal stimulus. Contrary to previous reports, these data suggest heightened pain sensitivity of the brain-gut axis in IBS, with a normal pattern of activation.     

Rectal sensory perception in females with obstructed defecation

PURPOSE: Parasympathetic afferent nerves are thought to mediate rectal filling sensations. The role of sympathetic afferent nerves in the mediation of these sensations is unclear. Sympathetic nerves have been reported to mediate nonspecific sensations in the pelvis or lower abdomen in patients with blocked parasympathetic afferent supply. It has been reported that the parasympathetic afferent nerves are stimulated by both slow ramp (cumulative) and fast phasic (intermittent) distention of the rectum, whereas the sympathetic afferent nerves are only stimulated by fast phasic distention. Therefore, it might be useful to use the two distention protocols to differentiate between a parasympathetic and sympathetic afferent deficit. METHODS: Sixty control subjects (9 males; median age, 48 (range, 20–70) years) and 100 female patients (median age, 50 (range, 18–75) years) with obstructed defecation entered the study. Rectal sensory perception was assessed with an infinitely compliant polyethylene bag and a computer-controlled air-injection system. This bag was inserted into the rectum and inflated with air to selected pressure levels according to two different distention protocols (fast phasic and slow ramp). The distending pressures needed to evoke rectal filling sensations, first sensation of content in the rectum, and earliest urge to defecate were noted, as was the maximum tolerable volume. RESULTS: In all control subjects, rectal filling sensations could be evoked. Twenty-one patients (21 percent) experienced no sensation at all in the pressure range between 0 and 65 mmHg during either slow ramp or fast phasic distention. The pressure thresholds for first sensation, earliest urge to defecate, and maximum tolerable volume were significantly higher in patients with obstructed defecation (P<0.001). In each subject, the pressure thresholds for first sensation, earliest urge to defecate, and maximum tolerable volume were always the same, regardless of the type of distention. CONCLUSION: Rectal sensory perception is blunted or absent in the majority of patients with obstructed defecation. The observation that this abnormality can be detected by both distention protocols suggests that the parasympathetic afferent nerves are deficient. Because none of the patients experienced a nonspecific sensation in the pelvis or lower abdomen during fast phasic distention, it might be suggested that the sympathetic afferents are also deficient. This finding implies that it is not worthwhile to use different distention protocols in patients with obstructed defecation.     

肠易激综合征患者直肠扩张后脑诱发电位的研究

目的 通过比较直肠扩张后脑诱发电位(CEP)的改变,探讨肠易激综合征(IBS)患者内脏高敏感性的发生机制,旨在进一步获得IBS感觉传入通路异常的客观依据。方法 根据罗马Ⅱ标准选择女性IBS患者10例,其中腹泻型6例,便秘型2例,腹泻-便秘交替型2例,另设7例女性健康志愿者为对照组,对其进行直肠气囊扩张,首先测出每例受试者感觉阈值,用1.5倍该阈值空气体积作为刺激(频率1Hz,连续100次,休息10分钟,重复一次),启动并记录两组受试者CEP的变化。结果 直肠节律性机械扩张引出可识别、可复制的CEP。与健康对照者相比,IBS患者N_1,P_1,N_2潜伏期明显缩短(P<0.05),同时,峰间波幅有增大趋势,但无统计学意义(P>0.05)。结论 IBS患者经直肠扩张后产生的CEP的改变证实了其内脏高敏感性及内脏传入通路的异常。     

Motor and sensory function of the rectum in different subtypes of constipation

BACKGROUND: It is not known whether evaluation of motor and sensory function of the rectum using a barostat may help to distinguish subtypes of constipation. METHODS: Motor and sensory function of the rectum have been evaluated using a barostat in 14 patients with slow transit constipation (STC), 12 patients with constipation-predominant irritable bowel syndrome (IBS) and 18 healthy controls. First minimal distending pressure was determined, after which spontaneous adaptive relaxation of the rectum was monitored. Then a step-wise isobaric distension procedure was performed, during which symptom perception was determined. The distension was followed by a 90-min barostat procedure: for 30 min in the basal state followed by ingestion of a semi-liquid meal (postprandial state). RESULTS: Minimal distending pressure was not different between both patient groups and controls, neither was compliance different between constipated patients and controls. The degree of spontaneous adaptive relaxation was in the same range in all groups. During distensions with high pressures, the perception of urge was significantly reduced in STC patients compared to IBS and controls, while the perception of pain was significantly increased in IBS versus STC and controls. Postprandially, a small decrease of rectal volume was only observed in the control group, but not in the patients. CONCLUSIONS: Rectal motor characteristics are not different between patients with constipation-predominant IBS, patients with STC and healthy controls while during isobaric distensions, sensations of urge were reduced in STC and sensations of pain were increased in IBS. Rectal visceroperception testing may help distinguish groups of patients with different subtypes of constipation.     

Gastric wall tension determines perception of gastric distention

BACKGROUND & AIMS: The primary mechanism that originates symptoms in response to gastric distention remains undefined. The aim of this study was to determine which factor, whether intragastric volume, pressure, or wall tension, determines perception of gastric distention. METHODS: Healthy subjects underwent increasing gastric distentions (2-minute duration at 5-minute intervals) either at fixed pressure levels using a conventional barostat (n = 10) or at fixed tension levels using a newly developed computerized tensostat (n = 12); perception was scored by a 0-6 scale. Distentions were performed during basal conditions (intravenous saline) and during gastric relaxation by glucagon administration (4.8 microgram/kg intravenous bolus plus 9.6 microgram. kg-1. h-1 infusion). RESULTS: Isobaric distentions with the conventional barostat produced more intense perception during glucagon (95% +/- 40% higher; P < 0.05). However, the factor that determined higher perception could not be ascertained, because at the same pressure levels both intragastric volume and wall tension were greater during glucagon administration (174% +/- 56% and 34% +/- 8% greater, respectively; P < 0.05 vs. saline for both). The tensostat evidenced that perception was selectively related to tension, not to elongation; during glucagon administration, intragastric volumes were significantly larger (80% +/- 28% larger increase; P < 0.05), but perception of isotonic distentions remained the same (27% +/- 22%; nonsignificant change). CONCLUSIONS: Gastric wall tension, but not intragastric volume, determines perception of gastric distention, at least below nociception.     

Longitudinal change in perceptual and brain activation response to visceral stimuli in irritable bowel syndrome patients

BACKGROUND & AIMS: Symptom-related fears and associated hypervigilance toward visceral stimuli may play a role in central pain amplification and irritable bowel syndrome (IBS) pathophysiology. Repeated stimulus exposure leads to decreased salience of threat and reduction of hypervigilance. We sought to evaluate hypervigilance in IBS visceral hypersensitivity and associated brain activity. METHODS: Twenty IBS patients (14 female; moderate to severe symptoms) and 14 healthy controls participated in symptom and rectal distention assessments 6 times over 12 months. In a subset of 12 IBS patients, H2 15O-positron emission tomography images were obtained during baseline, rectal distentions, and anticipation of an aversive distention during the first and last session. Statistical parametric mapping (SPM99) was used to identify areas and networks activated during each session as well as those with differential activation across the 2 sessions. RESULTS: Perceptual ratings of the rectal inflations normalized over 12 months, whereas IBS symptom severity did not. There were no sex-related differences in these response patterns. Stable activation of the central pain matrix was observed over 12 months, and activity in limbic, paralimbic, and pontine regions decreased. During the anticipation condition, there were significant decreases in amygdala, dorsal anterior cingulate cortex, and dorsal brainstem activation at 12 months. Covariance analysis supported the hypothesis of changes in an arousal network including limbic, pontine, and cortical areas underlying the decreased perception seen over the multiple stimulations. CONCLUSIONS: In IBS patients, repeated exposure to experimental aversive visceral stimuli results in the habituation of visceral perception and central arousal, despite stable activation of networks processing visceral pain and its anticipation.     

Alpha1-Antitrypsin Deficiency May Be a Risk Factor for Duodenal Ulcer in Patients with Helicobacter pylori Infection

Background: It is not known whether evaluation of motor and sensory function of the rectum using a barostat may help to distinguish subtypes of constipation. Methods: Motor and sensory function of the rectum have been evaluated using a barostat in 14 patients with slow transit constipation (STC), 12 patients with constipation-predominant irritable bowel syndrome (IBS) and 18 healthy controls. First minimal distending pressure was determined, after which spontaneous adaptive relaxation of the rectum was monitored. Then a step-wise isobaric distension procedure was performed, during which symptom perception was determined. The distension was followed by a 90-min barostat procedure: for 30 min in the basal state followed by ingestion of a semi-liquid meal (postprandial state). Results: Minimal distending pressure was not different between both patient groups and controls, neither was compliance different between constipated patients and controls. The degree of spontaneous adaptive relaxation was in the same range in all groups. During distensions with high pressures, the perception of urge was significantly reduced in STC patients compared to IBS and controls, while the perception of pain was significantly increased in IBS versus STC and controls. Postprandially, a small decrease of rectal volume was only observed in the control group, but not in the patients. Conclusions: Rectal motor characteristics are not different between patients with constipation-predominant IBS, patients with STC and healthy controls while during isobaric distensions, sensations of urge were reduced in STC and sensations of pain were increased in IBS. Rectal visceroperception testing may help distinguish groups of patients with different subtypes of constipation.     

Effect of continuous rectal distention on anal resting pressure

PURPOSE: Intermittent distention of the rectum induces internal anal sphincter relaxation, but whether continuous rectal distention might affect the resting pressure of the anal canal and the frequency of internal anal sphincter relaxations has not yet been investigated. The aim of this study was to record anal pressure under resting conditions and at two levels of continuous rectal distention. METHODS: Anal pressure was recorded by means of water-perfused catheters under resting conditions and at two levels of rectal distention controlled by an electronic barostat in eight healthy subjects. RESULTS: Continuous rectal distention did not significantly change mean anal resting pressure, but it did significantly decrease the amplitude of ultraslow waves (from 29±9 mmHg under resting conditions to 23±6 and 21±3 mmHg during lesser and greater rectal distention;P=0.017 andP=0.012, respectively) and increase the frequency of internal anal sphincter relaxations (from 1.3±1.3/hour under resting conditions to 8.8±4.3/hour and 11.0±4.8/hour during lesser and greater distention;P=0.012 in both comparisons). CONCLUSIONS: The resting pressure of the anal canal is maintained during continuous rectal distention. The decreased amplitude of ultraslow waves and increased frequency of the internal anal sphincter relaxations induced by rectal distention reveal a complex functional relationship between the rectum and the anal canal.Supported by the Associazione Amici della Gastroenterologia del Padiglione Granelli and the CARIPLO Foundation.     

Relationship of abdominal bloating to distention in irritable bowel syndrome and effect of bowel habit

BACKGROUND & AIMS: The relationship between the sensation of bloating, often ranked as the most bothersome symptom by patients with irritable bowel syndrome (IBS), and actual distention manifest as an increase in abdominal girth is controversial. Investigation of this problem has been hampered by the lack of a reliable ambulatory technique to measure abdominal girth. The aim of this study was to use the technique of abdominal inductance plethysmography to compare diurnal variation in girth in IBS patients and healthy volunteers, relating these changes to the sensation of bloating. METHODS: Abdominal girth was recorded for 24 hours in 20 IBS-constipation (age, 18-73 y), 20 IBS-diarrhea (age, 25-62 y) and 10 IBS-alternating (age, 21-59 y) female patients meeting Rome II criteria and 20 healthy female controls (age, 18-67 y). All subjects pursued normal daily activities, recording their symptoms of bloating and pain together with bowel habit. RESULTS: All patients with IBS, irrespective of bowel habit, reported significantly greater bloating than controls (P < .0001). Forty-eight percent of patients also showed distention beyond the 90% control range, with this being most prominent in IBS-constipation. Bloating correlated strongly only with distention in IBS-constipation (r > or = 0.48; P < or = .02). Neither bloating nor distention in IBS was related to body mass index, age, parity, or psychologic status. CONCLUSIONS: Abdominal distention is a clearly definable phenomenon in IBS that can reach 12 cm. However, it only occurs in half of patients reporting bloating, and the 2 only correlate in IBS-constipation. Bloating and distention may differ pathophysiologically and this appears to be reflected in the bowel habit subtype.     

Gastric distention correlates with activation of multiple cortical and subcortical regions

BACKGROUND & AIMS: The pathophysiology of functional dyspepsia may involve abnormal processing of visceral stimuli at the level of the central nervous system. There is accumulating evidence that visceral and somatic pain processing in the brain share common neuronal substrates. However, the cerebral loci that process sensory information from the stomach are unknown. The aim of this study was to localize the human brain regions that are activated by gastric distention. METHODS: Brain (15)O-water positron emission tomography was performed in 15 right-handed healthy volunteers during baseline and distal gastric distentions to 10 mm Hg, 20 mm Hg, threshold pain, and moderate pain. Pain, nausea, and bloating were rated during baseline and distentions (0-5 scale). Statistical subtraction analysis of brain images was performed between distentions and baseline. RESULTS: Symptoms increased with distending stimulus intensity (maximum pain, 2.1 +/- 0.4; nausea, 2.2 +/- 0.4; bloating, 3.7 +/- 0.2). Paralleling increases in distention stimulus and symptoms, progressive increases in activation (P < or = 0.05), were observed in the thalami, insula bilaterally, anterior cingulate cortex, caudate nuclei, brain stem periaqueductal gray matter, cerebellum, and occipital cortex. CONCLUSIONS: Symptomatic gastric distention activates structures implicated in somatic pain processing, supporting the notion of a common cerebral pain network.     

腹部冷刺激对肠易激综合征患者内脏感觉阈值的影响

目的 探讨腹部冷刺激对肠易激综合征（IBS）患者内脏褡珠影响。方法 通过脐部放置冰袋加直肠球囊内充气（时相性）和直肠球囊内注入冰水，观察46例IBS患者症状变化及直肠初始感觉阈值和排便阈值，并与13例健康人对照。结果 （1）脐部放置冰袋加直肠球囊内充气可诱发部分患者症状的产生，如腹痛、腹部不适等，但对初始感觉阈值和排便阈值无明显影响。（2）直肠球囊内注入冰水后，除便秘型IBS的排便阈值稍有所增加但差异不显著外，其余患者初始感觉阈值及排便阈值均明显低于对照组，以腹泻型变化最明显。结论 腹部冷刺激对IBS患者内脏感觉阈值无明显影响，而直肠内冷刺激可明显降低初始感觉阈值，说明IBS患者感觉过敏并非整体痛阈降低所致，而仅指内脏感觉过敏。     

The appreciation of rectal distention in fecal incontinence

The subjective response to rectal balloon sensation was assessed with anorectal manometry and pudendal nerve terminal motor latency measurement (PNTML) in three groups of patients. There were 37 healthy subjects, 54 patients with idiopathic fecal incontinence (IFI), and 36 with complete rectal prolapse and incontinence (CRP). There was no significant difference for any parameter of rectal balloon sensation between patients with IFI and normals. Patients with CRP differed only in onset (P=.001). The results show that the appreciation of rectal distention is maintained in IFI.