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。     

Visceral perception thresholds after rectal thermal and pressure stimuli in irritable bowel syndrome patients

BACKGROUND AND AIM: Visceral hypersensitivity has been shown to be present in irritable bowel syndrome (IBS). The current study sought to compare the characteristics of visceral perception thresholds after rectal thermal and pressure stimuli between IBS patients and healthy subjects. METHODS: A total of 46 patients with IBS were diagnosed using Rome II criteria. Thirteen healthy individuals participated in the study. Rectal visceral perception thresholds were examined in patients with IBS and in normal controls after thermal and pressure stimuli. Subjects were asked to report the sensation type, location, and spread. RESULTS: Compared with healthy subjects, IBS patients demonstrated significantly initially lower perception thresholds and defecation thresholds to rectal thermal and pressure stimuli, particularly in patients with diarrhea-predominant IBS. Ice stimuli on the abdominal wall had varied effects on symptoms in patients with IBS and did not affect perception thresholds. CONCLUSIONS: Visceral perception thresholds were decreased significantly after rectal thermal and pressure stimuli in patients with IBS. Visceral hypersensitivity may be one of the important pathogenic mechanisms in IBS.     

直肠内温度变化影响肠易激综合征患者内脏感觉阈值

目的 探讨直肠内温度及压力变化对肠易激综合征(IBS)患者内脏感觉阈值的影响，进一步研究IBS的发病机制。方法 通过直肠球囊内注入空气(压力刺激)、38℃温水、4℃冰水(温度刺激)及脐部放置冰袋加直肠球囊内充气，研究直肠温度和压力变化刺激对初始感觉阈值和排便阈值的影响。结果 (1)直肠球囊内注气后，IBS组患者的初始感觉阈值明显低于对照组，排便阈值差异不明显。IBS组中腹泻型与交替型患者的初始感觉阈值及排便阈值均明显降低；便秘型患者的初始感觉阈值稍低于对照组，排便阈值明显增高。(2)直肠球囊内注入4℃冰水后，除便秘型IBS的排便阈值稍有所增加外，其余患者初始感觉阈值及排便阈值均显著降低，以腹泻型变化最明显。(3)脐部放置冰袋可诱发部分患者产生症状，但对初始感觉阈值和排便阈值无明显影响。结论 直肠温度和压力刺激可明显降低IBS患者的初始感觉阈值和排便阈值，以腹泻型患者最显著。内脏对压力和温度的敏感性增高可能是IBS发病的重要机制之一。     

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.     

Novel techniques to study visceral hypersensitivity in irritable bowel syndrome

Visceral hypersensitivity has emerged as a key hypothesis in explaining the painful symptoms of irritable bowel syndrome (IBS), and it has been proposed as a “biologic marker” for the condition. Visceral hypersensitivity can be influenced by peripheral and central mechanisms affecting pain perception. The optimal method for its assessment in humans has not been determined. Current techniques include stimulation via the computerized barostat and electrical stimulation, response measures including the lower limb reflex, and brain imaging modalities such as functional MRI and positron emission tomography. It has been shown that IBS patients have decreased sensory thresholds to colonic and rectal balloon distention by barostat. Studies using electrical stimulation and the RIII lower limb reflex have further confirmed enhanced visceral perception in IBS. Evidence from more recent neuroimaging studies suggests that IBS patients have abnormal activation of brain circuits involved in emotional and cognitive modulation of sensory information, resulting in ineffective pain modulation; these circuits may have a pathophysiologic role in enhancing visceral perception. There are few effective pharmacologic treatments that relieve IBS symptoms, and improved understanding of brain-gut interactions and factors relating to enhanced visceral perception may guide us in developing more efficacious treatments.     

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.     

一氧化氮能神经调节异常在腹泻型肠易激综合征患者中的作用

目的　探讨一氧化氮 (NO)在肠易激综合征 (IBS)发病机制中的作用 ,并从基因水平揭示NO含量改变的原因。方法　 (1)应用电子气压泵及灌注导管测压仪研究 2 5例腹泻型IBS患者及 15例正常志愿者的肛门、直肠压力、直肠顺应性、乙状结肠和直肠运动指数以及直肠对容量刺激的感觉阈值 ;(2 )应用硝酸还原酶法测定两组肠黏膜NO的含量 ;(3)NADPH黄递酶组化法和计算机图像分析系统对两组肠黏膜肌层一氧化氮合酶 (NOS)阳性神经纤维作定量分析 ;(4)采用荧光定量PCR(FQ PCR)方法对神经型一氧化氮合酶 (nNOS)的基因表达进行定量分析。结果　 (1)肠道测压 :IBS患者的直肠静息压、肛管上部静息压、收缩压、松弛压、肛管下部静息压、收缩压、松弛压和直肠顺应性与正常人比较 ,差异无显著性 (P >0 .0 5 ) ;患者乙状结肠和直肠运动指数明显高于正常人 (P <0 .0 5 ) ;(2 )直肠内脏感觉阈值 :最低感觉阈值、排便阈值和疼痛阈值明显低于正常人 (P <0 .0 5 ) ;(3)肠黏膜NO含量 :患者结肠黏膜NO含量显著低于正常人 ,并且患者的NO含量与运动指数成负相关 ,与感觉阈值、排便阈值、疼痛阈值呈正相关 (P <0 .0 5 ) ;(4)NADPH组化染色 :IBS患者黏膜肌层NOS阳性神经纤维的面积和平均吸光度较正常人显著减少 (P <0 .0 5 ) ;(5 )NOS mRNA     

Sensitivity disturbances in patients with irritable bowel syndrome and fibromyalgia

BACKGROUND: Although visceral hypersensitivity is a common feature among patients with irritable bowel syndrome (IBS), studies on somatic sensitivity have given controversial results. AIM: To assess visceral sensitivity in response to isotonic rectal distensions and somatic sensitivity at different layers of the body wall (skin, subcutis, and muscle) in patients with IBS and fibromyalgia (FM), within and outside the area of abdominal pain referral. MATERIALS AND METHODS: We studied 10 patients with IBS, 5 patients with FM, 9 patients with IBS+FM, and 9 healthy controls. Rectal distensions were performed by increasing tension at 4 g steps up to 64 g or discomfort. Pain thresholds to electrical stimulation were measured within and outside the areas of abdominal pain referral. RESULTS: Patients with IBS and IBS+FM demonstrated rectal hypersensitivity in comparison to controls. The threshold of discomfort was 44 +/- 5 g in IBS and 36 +/- 5 in IBS+FM patients, while patients with FM and healthy controls tolerated all distensions without discomfort. In the areas of pain referral, pain thresholds of all three tissues of the body wall were lower than normal in all patients groups (p < 0.001). In control areas, the pain thresholds were normal in skin, and lower than normal in subcutis and muscle in IBS (p < 0.001). FM and IBS+FM demonstrated somatic hypersensitivity at all sites (p < 0.001 vs healthy). CONCLUSION: Our observations seem to indicate that, although sharing a common hypersensitivity background, multiple mechanisms may modulate perceptual somatic and visceral responses in patients with IBS and FM.     

Rectal Hypersensitivity Reduced by Acupoint TENS in Patients with Diarrhea-Predominant Irritable Bowel Syndrome: A Pilot Study

Our aim was to compare rectal perception of patients with diarrhea-predominant irritable bowel syndrome (IBS-D), constipation-predominant irritable bowel syndrome (IBS-C), functional constipation (FC), and healthy controls and to evaluate the therapeutic effect of acupoint transcutaneous electric nerve stimulation (TENS). Age- and sex-matched patients (24 IBS-D, 20 IBS-C, and 30 FC) were selected, and 30 volunteers served as healthy controls. Rectal sensory thresholds were evaluated by rectal balloon distension. Short- and long-term acupoint TENS was given respectively. IBS-D patients had significantly lower rectal sensory thresholds of the first sensation of stool, urgency of defecation, and pain than IBS-C or FC patients or healthy controls (P < 0.05), but there were no differences in rectal sensory thresholds among IBS-C and FC patients and healthy controls. In each group, females had significantly lower rectal sensory thresholds than males (P < 0.05), but there was no difference between younger (< or = 50 years old) and older (> 50 years old) patients. Short-term acupoint TENS increased rectal sensory thresholds of IBS-D patients. After 2-month acupoint TENS treatment in IBS-D patients, rectal sensory thresholds were significantly increased, stool times and the intensity of abdominal pain were decreased, and psychological scores were relieved to normal. Lowered rectal perception threshold is a hallmark of IBS-D patients. Females have significantly lower rectal sensory thresholds than males. Acupoint TENS is effective to treat IBS-D.     

Altered rectal perception in irritable bowel syndrome is associated with symptom severity

BACKGROUND & AIMS: Diverging results exist regarding the connection between altered visceral perception and gastrointestinal (GI) symptoms, as well as the effects of psychological status on visceral sensitivity. We sought to investigate different aspects of rectal perception in irritable bowel syndrome (IBS) and the association with GI and psychological symptoms. METHODS: We included 109 patients with IBS meeting Rome II criteria (77 women; age range, 20-71 years) and 29 healthy controls (21 women; age range, 20-68 years). They underwent rectal balloon distentions determining sensory thresholds for discomfort and pain, the perceived intensity of unpleasantness, and the viscerosomatic referral area. The fifth percentile (thresholds) and 95th percentile (unpleasantness and referral area) in controls were used to define altered perception. Questionnaires were used to assess severity of IBS-related GI symptoms and psychological symptoms. RESULTS: When combining the 3 aspects of perception, 67 patients (61%) had altered rectal perception. These patients, compared with normosensitive patients, more frequently reported moderate or severe pain (73% vs 44%; P < .01), bloating (73% vs 36%; P < .0001), diarrhea (47% vs 21%; P < .01), satiety (39% vs 13%; P < .01), and clinically significant anxiety (31% vs 12%; P < .05). In a multivariate analysis, only pain and bloating remained associated with altered rectal perception. CONCLUSIONS: Altered rectal perception is common in IBS and seems to be one important pathophysiologic factor associated with GI symptom severity in general and pain and bloating in particular. It is not just a reflection of the psychological state of the patient.     

The selective serotonin reuptake inhibitor fluoxetine does not change rectal sensitivity and symptoms in patients with irritable bowel syndrome: a double blind, randomized, placebo-controlled study.

BACKGROUND & AIMS: Although widely prescribed, the evidence for the use of antidepressants for the treatment of irritable bowel syndrome (IBS) is limited. In this study, we hypothesized that fluoxetine (Prozac), a selective serotonin reuptake inhibitor, has visceral analgesic properties, leading to increased sensory thresholds during rectal distention and improvement of symptoms, in particular in IBS patients with visceral hypersensitivity. METHODS: Forty non-depressed IBS patients underwent a rectal barostat study to assess the sensitivity to rectal distention before and after 6 weeks of treatment with fluoxetine 20 mg or placebo. Abdominal pain scores, individual gastrointestinal symptoms, global symptom relief, and psychologic symptoms were assessed before and after the intervention. RESULTS: At baseline, 21 of 40 patients showed hypersensitivity to rectal distention. Fluoxetine did not significantly alter the threshold for discomfort/pain relative to placebo, either in hypersensitive (19 +/- 3 vs. 22 +/- 2 mm Hg above MDP) or in normosensitive (34 +/- 2 vs. 39 +/- 4 mm Hg above MDP) IBS patients. Overall, 53% of fluoxetine-treated patients and 76% of placebo-treated patients reported significant abdominal pain scores after 6 weeks (not significant). In contrast, in hypersensitive patients only, fluoxetine significantly reduced the number of patients reporting significant abdominal pain. Gastrointestinal symptoms, global symptom relief, and psychologic symptoms were not altered. CONCLUSIONS: Fluoxetine does not change rectal sensitivity in IBS patients. Possible beneficial effects on pain perception need to be confirmed in larger trials.     

Study on functional constipation and constipation‐predominant irritable bowel syndrome by using the colonic transit test and anorectal manometry

OBJECTIVE: To investigate the visceral perception, anorectal pressure and colonic transit time (CTT) in patients with functional constipation and constipation‐predominant irritable bowel syndrome (C‐IBS), and to study the manometric abnormalities of these two conditions. METHODS: The CTT in patients with functional constipation and C‐IBS was studied by using radiopaque markers. Rectal visceral perception thresholds, rectal compliance and anorectal pressure were examined by electric barostat. RESULTS: The CTT in both groups of constipated patients was abnormal. A lot of radiopaque markers remained in the right colon in C‐IBS patients, whereas in patients with functional constipation, the radiopaque markers remained in each segment of the colon. The anorectal resting pressure, squeezing pressure and relaxation pressure were normal in both groups. Rectal compliance and defecation thresholds were much higher compared with controls, and the rectal visceral perception of functional constipation was also abnormal. CONCLUSIONS: The motility abnormalities of functional constipation and C‐IBS occurred in different colonic segments. Results suggest that CTT measure­ment and anorectal manometry could be helpful in the differential diagnosis of these two conditions.     

慢性特发性便秘患者肛门直肠测压表现及西沙必利的疗效研究

目的研究慢性特发性便秘（CIC）患者肛门直肠动力及直肠对容量刺激感觉的变化，同时观察西沙必利对CIC的疗效及对上述指标的影响。方法用肛门直肠测压法检测30例CIC患者，服用西沙必利前后的直肠动力及直肠对容量刺激感觉的变化。20名健康者作对照。结果肛门直肠括约肌最大收缩压降低（P＜0．05），引起直肠肛门抑制性反射的最小松弛容量（MRV）增大（P＜0．05），直肠内部容量刺激的排便阈值及疼痛阈值均明显增加（P＜0．01）；西沙必利10mg每日3次治疗4周可显著改善CIC患者上述异常改变（P＜0．01），增加CIC患者排便次数（P＜0．01），治疗总有效率为46，67％。结论CIC患者存在肛门直肠动力及内脏感觉异常，西沙必利可改善上述异常表现，对约半数CIC患者具有良好疗效。     

H. pylori infection and visceral hypersensitivity in patients with irritable bowel syndrome

BACKGROUND/AIM: Irritable bowel syndrome (IBS) is characterized by abdominal pain and changes in stool habits. Visceral hypersensitivity (VH) is a key factor in the pathophysiology of IBS. The role of Helicobacter pylori infection in the induction of VH in the upper gastrointestinal tract is controversially discussed. The aim of this study is to evaluate the value of rectal barostat in eliciting abdominal symptoms in patients with IBS in relation to H. pylori infection. PATIENTS AND METHODS: 31 patients (19 female, 12 male, mean age 45.6 +/- 10 years) with normal colonoscopy and clinical signs of IBS were examined by rectal barostat (pressure-controlled balloon distension in the rectum). Induction of typical abdominal discomfort (far from the balloon) defined the examination positive. Level of nonpainful perception (L1), feeling of defecation (L2), and pain or stool urgency (L3) were registered in comparison with a healthy control group (CG; n = 15, 9 female, 6 male). The H. pylori status was defined by (13)C-urea breath test (n = 46). RESULTS: Typical abdominal discomfort was induced in 9 patients (pain group, PG) by pressure-controlled rectal distension (H. pylori status: 8 positive, 1 negative). Patients not presenting with abdominal pain to rectal distension (nonpain group, NPG) were all H. pylori negative (p < 0.001). L3 as an indicator of VH was reached at a lower pressure threshold in PG than in NPG or CG (p < 0.05). The perception was not different between NPG and CG (p > 0.05). CONCLUSIONS: The induction of typical abdominal discomfort in patients with IBS by the use of rectal barostat occurred predominantly in H. pylori infected patients and suggests that H. pylori infection may be involved in triggering VH in patients with IBS. Further studies in larger patient groups and after H. pylori eradication therapy are needed to confirm and extend this observation.     

健康人冷应激前后直肠感觉和自主神经功能的变化

背景应激可以影响消化道内脏感觉功能,冷应激是一有效的应激刺激.目的研究冷应激前后直肠感觉阈值和自主神经张力的变化,探讨自主神经功能改变对直肠敏感性的影响.方法符合入选标准的健康志愿者15名,用电子恒压器测定直肠对气囊扩张的感觉阈值,同时分析心率变异性(HRV)以反映自主神经张力.数日后采用冷水浸手获得应激状态后重复上述实验.结果冷应激状态下,受试者初次感觉、初次排便感觉和便意窘迫感的容量阈值显著升高(P＜0.05);HRV频域分析显示低频带功率(P1)和低、高频带功率比(P1/P2)显著升高(P＜0.05).结论冷应激时直肠对容量刺激的敏感性降低可能与交感神经兴奋性升高有关.     

Visceral sensitivity and symptoms in patients with constipation- or diarrhea-predominant irritable bowel syndrome (IBS): effect of a low-fat intraduodenal infusion

BACKGROUND: Visceral hypersensitivity is common in Irritable Bowel Syndrome (IBS) patients, and symptoms exacerbate postprandially. Yet the effects of nutrients on visceral sensitivity and symptoms in these patients have not been fully explored. AIMS: To evaluate the differences of visceral sensitivity and symptoms in healthy subjects and IBS patients during fasting and intraduodenal lipids infusion. METHODS: Graded rectal distensions at fixed tension levels were performed in 16 IBS patients (8 IBS-C and 8 IBS-D) and 6 healthy subjects before and during intraduodenal lipids infusion at 0.5 kcal/min. Tension levels were increased in 4 gr increments up to 64 gr or discomfort during both conditions. At each step, perception and symptoms were measured by means of a validated questionnaire. RESULTS: In basal conditions, perception thresholds in IBS patients and health were, respectively, 8 +/- 2 gr versus 32 +/- 9 gr (p < 0.001) with no changes during lipids. Intraduodenal lipids infusion significantly lowered threshold of discomfort in IBS patients in comparison to fasting (24 +/- 6 gr vs 34 +/- 4 gr; p < 0.05), while health tolerated all distension without discomfort. No differences of compliance, perception, or discomfort were observed between the two subgroups of patients at each tension step. The predominant symptom elicited in patients with IBS-C was abdominal pain (54%), while patients with IBS-D exhibited urgency (63%, p < 0.005); this pattern was maintained during lipids. CONCLUSIONS: Intraduodenal lipids increase visceral sensitivity in both IBS-C and IBS-D; symptoms specificity in response to rectal distension is maintained in the postprandial period. Lipids may be responsible for the postprandial symptoms exacerbation in IBS.     

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。     

Gender-related differences in visceral perception in health and irritable bowel syndrome

BACKGROUND: Irritable bowel syndrome (IBS) is more common in female subjects, and IBS patients generally exhibit reduced pain thresholds to rectal distension. The aim of the present paper was to determine gender-related differences in rectal perception in both healthy controls and IBS patients. METHODS: Fifty-nine IBS patients (age 20-65 years; mean, 39.2 years; 31 women, 28 men) with symptoms that fulfilled Rome-II criteria and 21 healthy controls (age 25-58 years; mean, 37.8 years; 11 women, 10 men) were recruited. Participants completed a questionnaire regarding bowel symptoms and psychological distress, and maximal tolerable pressures were evaluated via barostat tests. RESULTS: Although healthy women appear to have lower perception thresholds than men, significant gender differences in pain sensitivity were not detected (P > 0.05). In addition, female patients with IBS also exhibited no enhanced colorectal perception, as compared with male IBS patients (P > 0.05). CONCLUSIONS: No gender differences in visceral perception were determined to exist between the healthy controls and the IBS patients. Therefore, the increased prevalence of IBS in women may be related to another set of pathophysiological factors, and not to gender-related differences in visceroperception.     

Heightened visceral sensation in functional gastrointestinal disease is not site-specific

Alteration in visceral sensation locally at the site of presumed symptom origin in the gastrointestinal tract has been proposed as an important etiopathological mechanism in the so-called functional bowel disorders. Patients presenting with one functional gastrointestinal syndrome, however, frequently have additional symptoms referable to other parts of the gut, suggesting that enhanced visceral nociception may be a panintestinal phenomenon. We measured the sensory thresholds for initial perception (IP), desire to defecate (DD), and urgency (U) in response to rectal balloon distension, and the thresholds for initial perception and for discomfort in response to esophageal balloon distension in 12 patients with irritable bowel syndrome (IBS) and 10 patients with functional dyspepsia (FD), in comparison with healthy controls. As expected, IBS patients exhibited lower rectal sensory thresholds than controls (P<0.0001), but in addition had significantly lower sensory thresholds for both perception and discomfort evoked by balloon distension of the esophagus (mean ±SEM: 8.8±1.3 ml vs 12.1±1.5 ml (P<0.05) and 12.2±1.4 ml vs 16.4±1.4 ml (P<0.02) respectively. Patients with FD showed similarily enhanced esophageal sensitivity, with thresholds for perception and discomfort of 8.1±0.9 ml (P<0.02), and 10.1±1.0 ml (P<0.001), respectively, but were also found to have sensory thresholds for rectal distension similar to those observed in the IBS group, significantly lower than in controls: IP 45.0±17.6 vs 59.3±1.5 ml (P<0.001), DD 98.0±17.9 vs 298.7±9.0 ml (P<0.0001), U 177.2±25.4 vs 415.1 ±12.6 ml (P<0.0001). Somatic nerve sensory thresholds showed no significant differences between the patient and control groups. Our findings indicate that alterations in visceral sensitivity in functional gastrointestinal disease affect sites in the gut other than the putative organ of symptom origin, supporting the concept of generally enhanced visceral awareness in patients with functional bowel disorders.     

Effect of acute physical and psychological stress on gut autonomic innervation in irritable bowel syndrome

BACKGROUND & AIMS: Stress is an important causative factor in irritable bowel syndrome (IBS). It remains unknown whether stress-related changes in gut function are mediated by altered autonomic efferent gut-specific innervation. We studied the effect of acute physical and psychological stress on autonomic innervation and visceral sensitivity in healthy volunteers and patients with IBS. METHODS: Twenty-four patients (20 women) with constipation-predominant IBS and 12 healthy volunteers (8 women) underwent either physical (cold water hand immersion) or psychological (dichotomous listening) stress on separate occasions. Assessments included stress perception (visual analogue scale), gut-specific autonomic innervation (rectal mucosal blood flow [RMBF] by laser Doppler flowmetry), and viscerosomatic sensitivity (anal and rectal electrosensitivity). RESULTS: Patients with IBS had a heightened baseline perception of stress (P < .01). RMBF decreased during physical stress (29.6% +/- 2.8% and 28.7% +/- 3.9%) and psychological stress (24.4% +/- 2.1% and 23.5% +/- 4.3%) in patients with IBS and controls, respectively (mean +/- SEM). During physical stress, rectal perception (23.2% +/- 6% vs .6% +/- 3% [IBS vs control group, P < .05]) and rectal pain thresholds (27.0% +/- 4% vs 1.3% +/- 5%, P < .001) decreased in patients with IBS only. Psychological stress reduced thresholds for rectal perception (19.4% +/- 6% vs 8% +/- 6%, P < .01) and rectal pain (28.4% +/- 4% vs 3.4% +/- 3.8%, P < .001) in patients with IBS only. Acute stress elevated anal perception thresholds in patients with IBS but not controls (physical stress: 14.7% +/- 14% vs -9.3% +/- 11%, P < .05; psychological stress: 24.7% +/- 9% vs 11% +/- 11%, P < .05). CONCLUSIONS: Acute stress alters gut-specific efferent autonomic innervation in both controls and patients with IBS, although normalization is delayed in IBS. By contrast, only patients with IBS show heightened visceral sensation, suggesting involvement of a different regulatory mechanism, either central or peripheral.