Abdominal pain impacts quality of life in women with irritable bowel syndrome

OBJECTIVES: Patients with irritable bowel syndrome (IBS) report lower health-related quality of life (QoL) as compared to healthy controls. The aims of this analysis were to describe which IBS symptoms were rated on a daily diary as most distressing/severe by IBS women, and determine which IBS symptoms were most predictive of lower QoL and have the greatest impact on daily life. METHODS: This report is a secondary analysis of prospective and retrospective symptom severity and impact data, collected on 242 women with IBS, aged 18-48, who were studied between 1997 and 2004. RESULTS: On the daily diary, intestinal gas was the most frequent IBS symptom with subjects reporting at least minimal intestinal gas on 74% of days and moderate or worse severity on 27% of days. Abdominal pain occurred at least minimally on 62% of days. Diarrhea was the least common. Across women, abdominal pain was most strongly related to life impact variables and QoL, followed by intestinal gas and bloating. Analysis of day-to-day variation within women showed that abdominal pain was most strongly correlated with daily life impact variables and constipation had the weakest correlation. While diarrhea had a lower correlation with life impact, this was due to the low prevalence of diarrhea. When it occurs, diarrhea has a large impact. Partial correlation analysis showed that the impact of diarrhea is independent of abdominal pain. CONCLUSION: Abdominal pain is the most disruptive IBS symptom. Diarrhea also has an independent and significant impact when it occurs, especially in those with diarrhea-predominant IBS.     

Gender Differences in Gastrointestinal, Psychological, and Somatic Symptoms in Irritable Bowel Syndrome

In the United States, more women than men seek health-care services for symptoms of irritable bowel syndrome (IBS). A number of explanations are given for this gender difference including the higher rates of somatic non-gastrointestinal symptoms and increased psychological distress reported by women with IBS. However, these gender differences are found in studies that rely on retrospective recall with little attention to age or reproductive status. The purpose of the current analysis was to prospectively compare the frequency (days/month of moderate to severe based on a daily diary) of somatic, gastrointestinal (GI), and psychological distress symptoms, in menstruating women (N = 89) and postmenopausal women (N = 66) to men (N = 32) with IBS. In addition, the correlation between daily symptoms and daily report of overall health was evaluated. Postmenopausal women reported significantly more GI pain/discomfort symptoms, especially bloating and abdominal distension, than men, however these differences are greatly attenuated when age is controlled for. Both postmenopausal and menstruating women reported significantly more somatic symptoms (especially joint pain and muscle pain) than men with IBS. The effect was stronger in postmenopausal women, whose somatic symptoms were also higher than menstruating women (P = 0.014). Fatigue and stress were higher in women than men but anxiety and depression were not. All three types of symptoms were strongly correlated with self-rating of health, both across and within-person. Gender-related differences in GI and somatic symptoms are apparent in persons with IBS, more strongly in postmenopausal women. The presence of somatic symptoms in postmenopausal women with IBS may challenge clinicians to find suitable therapeutic options.     

Daily gastrointestinal symptoms in women with and without a diagnosis of IBS

This study compared daily gastrointestinal symptoms and stool characteristics across two menstrual cycles, and recalled bowel symptoms and psychological distress in women with irritable bowel syndrome (IBS,N=22), IBS nonpatients (IBS-NP,N=22), and controls (N =25). Daily reports of abdominal pain, bloating, intestinal gas, constipation, and diarrhea did not differ significantly between the IBS and IBS-NP groups but both groups reported significantly higher symptoms than the control group. Stool consistencies was significantly looser in the IBS group relative to the control group. Menstrual cycle effects on symptoms were noted in all the groups. There were no significant differences in psychological distress between women with IBS, and IBS-NP, but both groups reported significantly higher global distress than the control group. The lack of difference between the IBS and IBS-NP groups in contrast to the results of others, can be understood in terms of differences in recruitment strategies.This work was supported by the National Institute for Nursing Research, NIH, grant NR01094.     

Tegaserod: a new 5-HT4 agonist.

Tegaserod is a medication that has been shown to be of benefit in women with irritable bowel syndrome (IBS) associated with abdominal pain, bloating, and constipation. Tegaserod is a selective serotonin receptor subtype 4 partial agonist designed to interact with the network of cells and nerves throughout the gastrointestinal tract that use serotonin. Tegaserod has been shown to modulate both gastrointestinal motility and visceral sensitivity. Specifically, it increases the peristaltic reflex and decreases visceral sensitivity. Clinical studies have shown that tegaserod improves symptoms of abdominal pain, bloating, and constipation in women with IBS. This article discusses the role of serotonin in gastrointestinal tract physiology, the structure and pharmacokinetic profile of tegaserod, and clinical applications of this new drug.     

Bacterial concepts in irritable bowel syndrome

An overlap of symptoms in irritable bowel syndrome (IBS) exists across subtype groups. Symptoms include intestinal gas, diarrhea, dyspepsia, bloating, abdominal pain, and constipation. The unifying symptom may be excessive intestinal gas as a by-product of intestinal microbial fermentation. Abnormal fermentation of food takes place when gut microbes expand proximally into the small intestine instead of being confined predominantly to the colon. Such proximal expansion of indigenous gut microbes or small intestinal bacterial overgrowth (SIBO) may lead to activation of host mucosal immunity and an increase in intestinal permeability to result in flu-like extra-intestinal symptoms that accompany the classic IBS symptoms of altered bowels. The presence of methane on lactulose breath testing is associated with constipation-predominant IBS. Antibiotic therapy may be appropriate to treat underlying SIBO in IBS patients. Seventy-five percent improvement of IBS symptoms was reported in a double-blind, placebo-controlled study once antibiotics succeeded in treating bacterial overgrowth. Once a good clinical response and normalization of the lactulose breath test are achieved, a prokinetic agent may be used to stimulate phase III of interdigestive motility to delay relapse of bacterial overgrowth.     

Current gut-directed therapies for irritable bowel syndrome

Opinion statement Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that can present with a wide array of symptoms that make treatment difficult. Current therapies are directed at relieving symptoms of abdominal pain or discomfort, bloating, constipation, and diarrhea. Pharmacologic agents used to treat IBS-associated pain include myorelaxants, peppermint oil, and peripherally acting opiates. Dicyclomine and hyoscyamine, the two myorelaxants available in the United States, have not been proven effective in reducing abdominal pain in patients with IBS. The efficacy of peppermint oil is debated, but methodological problems with existing studies preclude definitive judgment. Loperamide is ineffective for relief of abdominal pain. For IBS patients with excessive abdominal bloating, a small number of studies suggest that bacterial eradication with gut-directed antibiotics and bacterial reconstitution with nonpathogenic probiotics may reduce flatulence. For constipation-predominant (C-IBS) symptoms, current treatment options include fiber supplementation, polyethylene glycol, and tegaserod. Soluble fibers (ispaghula, calcium polycarbophil, psyllium) are more effective than insoluble fibers (wheat bran, corn fiber) in alleviating global symptoms and relieving constipation, although fiber in general has marginal benefit in treatment of overall IBS symptoms. Polyethylene glycol increases bowel frequency in chronic constipation, but its overall efficacy against IBS is unclear. Tegaserod, a 5-HT₄ agonist, demonstrates superiority over placebo in improving bowel frequency and stool consistency and alleviating abdominal pain and bloating in women with C-IBS. Overall global symptoms are modestly improved with tegaserod when compared with placebo. Additional agents under investigation for C-IBS include the ClC₂ chloride channel opener lubiprostone, μ-opioid receptor antagonist alvimopan, and 5-HT₄ agonist renzapride. For diarrhea-predominant (D-IBS) symptoms, available therapies include loperamide, alosetron, and clonidine. Alosetron, a 5-HT₃ antagonist, is superior to placebo for reducing bowel frequency, improving stool consistency, and relieving abdominal pain in women with D-IBS. However, alosetron is available under a restricted license because of concerns for ischemic colitis and severe constipation necessitating colectomy. Clonidine may be helpful in alleviating global symptoms for D-IBS patients.     

Gastrointestinal Symptoms in Women With Endometriosis and Microscopic Colitis in Comparison to Irritable Bowel Syndrome: A Cross-Sectional Study

Background: Gastrointestinal (GI) symptoms similar to irritable bowel syndrome (IBS) are often present in women with endometriosis and microscopic colitis (MC). The objective of this study was to estimate GI symptoms in IBS, endometriosis, and MC, to compare the clinical expression of the diseases.Methods: Women with IBS, endometriosis, and MC were identified by diagnosis codes at a tertiary center. The patients had to complete the visual analog scale for IBS to estimate specific GI symptoms. Women fulfilling Rome III criteria for IBS were diagnosed as IBS (n = 109) and divided into subgroups depending on predominating symptoms. Women diagnosed with endometriosis (n = 158) and MC (n = 88) were evaluated whether they also fulfilled the Rome III criteria for IBS.Results: Women with IBS experienced aggravated abdominal pain, diarrhea, bloating and flatulence, nausea and vomiting, the urgency to defecate, the sensation of incomplete evacuation and intestinal symptom’s influence on daily life, and impaired psychological well-being, compared to women with endometriosis. When patients with endometriosis also fulfilled the criteria for IBS, all symptoms in the 2 cohorts, except intestinal symptom’s influence on daily life, were equal. Women with IBS or diarrhea-predominated IBS experienced aggravated abdominal pain, bloating and flatulence, intestinal symptom’s influence on daily life, and impaired psychological well-being compared to MC, but at equal levels as MC with IBS-like symptoms.Conclusions: Women with IBS generally experience aggravated GI symptoms and impaired psychological well-being compared to endometriosis and MC. Patients with endometriosis or MC, in combination with IBS, express similar symptoms as patients with sole IBS.     

Intestinal Gas Production from Bacterial Fermentation of Undigested Carbohydrate in Irritable Bowel Syndrome

The relationship between abdominal pain and bowel gas from bacterial fermentation of undigested carbohydrate was investigated in nine patients with irritable bowel syndrome (IBS), six lactose malabsorbers, and 11 asymptomatic controls. All subjects took breath samples and marked analog scales for abdominal pain, bloating, and psychological stress hourly during all waking hours for 7 days. Breath samples were analyzed for hydrogen concentration within 3 days, and the concentration was corrected for storage time. Symptoms of pain and bloating were significantly more common in IBS patients than in lactose malabsorbers or normal controls, and pain was significantly correlated with bloating in IBS patients. Breath hydrogen concentration was similar in all three groups, and breath hydrogen was not correlated with pain ratings in IBS patients. Thus, abdominal pain may be related to bloating from gastrointestinal gas, but bacterial fermentation cannot be the cause of such gas. The most likely source is swallowed air. This study also demonstrates the feasibility of monitoring hydrogen production in the bowel in field studies by having subjects collect hourly breath samples.     

Breath tests and irritable bowel syndrome

Breath tests are non-invasive tests and can detect H2and CH4 gases which are produced by bacterial fermentation of unabsorbed intestinal carbohydrate and are excreted in the breath.These tests are used in the diagnosis of carbohydrate malabsorption,small intestinal bacterial overgrowth,and for measuring the orocecal transit time.Malabsorption of carbohydrates is a key trigger of irritable bowel syndrome(IBS)-type symptoms such as diarrhea and/or constipation,bloating,excess flatulence,headaches and lack of energy.Abdominal bloating is a common nonspecific symptom which can negatively impact quality of life.It may reflect dietary imbalance,such as excess fiber intake,or may be a manifestation of IBS.However,bloating may also represent small intestinal bacterial overgrowth.Patients with persistent symptoms of abdominal bloating and distension despite dietary interventions should be referred for H2 breath testing to determine the presence or absence of bacterial overgrowth.If bacterial overgrowth is identified,patients are typically treated with antibiotics.Evaluation of IBS generally includes testing of other disorders that cause similar symptoms.Carbohydrate malabsorption(lactose,fructose,sorbitol)can cause abdominal fullness,bloating,nausea,abdominal pain,flatulence,and diarrhea,which are similar to the symptoms of IBS.However,it is unclear if these digestive disorders contribute to or cause the symptoms of IBS.Research studies show that a proper diagnosis and effective dietary intervention significantly reduces the severity and frequency of gastrointestinal symptoms in IBS.Thus,diagnosis of malabsorption of these carbohydrates in IBS using a breath test is very important to guide the clinician in the proper treatment of IBS patients.     

The effects of probiotics on symptoms of irritable bowel syndrome]

BACKGROUND/AIMS: Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) tract disorder that has heterogeneous clinical presentations such as abdominal pain, diarrhea, constipation, and abdominal distension. It is known that several mechanisms are involved in the pathogenesis of IBS. Probiotics may target one or more pathophysiologic pathways in IBS and may improve the symptoms of IBS. However, the results of studies about probiotics on IBS are controversial. Therefore, the aim of this study was to evaluate the effect of probiotics on GI symptoms and intestinal gas volume changes in patients with IBS. METHODS: Forty patients were randomly allocated to be treated with Medilac DS (Bacillus subtilis, Streptococcus faecium) (n=20) or placebo (n=20) in a double-blind, prospective manner. The change in intestinal gas volume and symptom scores after 4-week treatment were evaluated for the efficacy. RESULTS: There was no significant difference in bloating, frequency of gas expulsion, frequency of defecation, and hardness of stool before and after the treatment. However, the severity of abdominal pain and the frequency of abdominal pain decreased significantly in Medilac DS group (2.4+/-1.3 cm/day --> 1.6+/-1.6 cm/day, 1.7+/-1.3/day --> 1.0+/-1.0/day) (p=0.044, p=0.038), but not in placebo group (2.1+/-2.0 cm/day --> 1.8+/-2.1 cm/day, 1.3+/-1.2/day --> 1.4+/-1.9/day). In both groups, intestinal gas volume at baseline, after 2-week treatment, and after 4-week treatment did not show significant change. Medilac DS was well tolerated without adverse events. CONCLUSIONS: Medilac DS is a safe and useful probiotic agent for the treatment of abdominal pain in patients with IBS.     

Gender-related differences in IBS symptoms

OBJECTIVE: Women are more likely than men to report irritable bowel syndrome (IBS) symptoms as well as chronic visceral and musculoskeletal pain. The study tests the general hypothesis that female IBS patients differ from their male counterparts in symptoms related to the viscera and musculoskeletal system, and that these differences are related to the menstrual cycle. METHODS: Seven hundred fourteen Rome positive IBS patients were evaluated for GI and extracolonic symptoms, psychological symptoms (SCL-90R), and quality of life (QOL) (SF-36). In addition, 54 postmenopausal women were compared with 61 premenopausal women and 54 age-matched males, all with IBS. RESULTS: Male and female subjects reported similar GI levels of symptom severity and psychological problems. Abdominal distension associated with a sensation of bloating was more commonly reported by female patients, as were symptoms of constipation. Female patients more often reported nausea, alterations of taste and smell, and unpleasant sensations on the tongue, muscle stiffness in the morning, greater food sensitivity, and side effects from medications. Forty percent of female patients reported menstrual cycle-related worsening of symptoms, but few symptom differences were found between pre- and postmenopausal women, making it unlikely that most of the gender differences observed are directly tied to the menstrual cycle. CONCLUSIONS: Female patients report higher levels of a variety of intestinal and nonintestinal sensory symptoms despite similar levels of IBS severity, abdominal pain, psychological symptoms, and illness impact. The apparent differences in sensitivity to nonpainful visceral sensations, medications, and food may represent altered sensory processes, autonomic responses, and/or cognitive hypervigilance.     

Bloating in constipation: relevance of intraluminal gas handling

The symptom of bloating and sometimes associated increase in abdominal girth (distension) is often described by patients as very intrusive, significantly impacting their quality of life. Indeed many patients rank it as their most bothersome symptom, even above abdominal pain. Despite this fewer patients appear to seek medical attention for this problem compared with other gastrointestinal symptoms. This has been attributed to the fact that most sufferers usually have other symptoms, such as abdominal pain, which they may perceive as potentially more serious, and hence seek preferential medical advice and treatment. This review aims to clarify the meaning of the terms bloating and distension, explores their association with constipation, and discusses possible pathophysiologies, in particular the relevance of intraluminal gas handling.     

Sensation of bloating and visible abdominal distension in patients with irritable bowel syndrome

OBJECTIVES: Abdominal bloating and distension are common symptoms of irritable bowel syndrome (IBS). The postulated pathophysiological mechanisms underlying these symptoms include increased production, retention, or perception of gas or luminal contents. The aims of this study were to prospectively compare the prevalence of, and clinical factors related to, bloating and distension in an IBS patient population. METHODS: A total of 714 consecutive patients who met Rome I criteria for IBS were prospectively surveyed, and were classified as having bloating alone (B) or bloating and distension (B+D) based on a comprehensive bowel symptom questionnaire. GI, extraintestinal, and psychological symptoms, as well as health-related quality of life measures were also assessed using validated survey instruments. RESULTS: A total of 542 IBS patients (76%) who reported abdominal bloating were studied. Of these, 132 patients fulfilled criteria for the B group, whereas 410 patients fulfilled criteria for the B+D group. There was a significantly different gender distribution in the B and B+D groups (female:male ratios, 1.4:1 and 2.8:1, respectively p < 0.02). There was also a significantly different bowel habit subgroup distribution, with a greater predominance of constipation in B+D group and of diarrhea in the B group (p < 0.03). Both groups were similar in other clinical parameters, including progressive worsening of symptoms during the day, and relief by passing stool or gas. Both bloating and distension worsened when other abdominal symptoms worsened. Abdominal distension was associated with greater symptom severity and less diurnal variation in symptoms, and was less often perceived as associated with food intake. CONCLUSIONS: Bloating and visible abdominal distension may arise from two distinct but interrelated physiological processes. Although the sensation of bloating may be related to enhanced sensitivity to visceral afferent stimulation, abdominal distension in more severely affected patients may be related to triggering of a visceromotor reflex affecting the tone of abdominal wall muscles.     

Importancia de la dieta en el síndrome del intestino irritable

About two-thirds of irritable bowel syndrome (IBS) patients associate their symptoms with certain foods. We reviewed food-related factors putatively associated with manifestations of IBS. Soluble fiber may improve constipation but frequently increases bloating and abdominal pain. Carbohydrate malabsorption seems to be more frequent in IBS. A low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet significantly reduces IBS symptoms and has been suggested as a therapeutic option. Serological screening for celiac disease should be done in patients without constipation. Moreover, non-celiac disease gluten sensitivity, defined as gluten intolerance once celiac disease and wheat allergy have been ruled out, should be considered in these patients. There is no specific diet for IBS patients but small and frequent meals, avoiding greasy foods, dairy products, many carbohydrates, caffeine and alcohol, is recommended.     

Abdominal Symptoms and Anorectal Function in Health and Irritable Bowel Syndrome

Background: It is unclear how the quality and quantity of abdominal symptoms and anorectal function differ between irritable bowel syndrome (IBS) patients and healthy controls, and whether different anorectal function in patients is associated with abdominal symptoms in IBS. Methods: Fifty-two outpatients with IBS and 12 healthy controls kept daily symptom records over 1 week. At the end of the week, anorectal function was assessed by manovolumetry before and after a standard fatty meal. Patients were divided into symptom and manovolumetric subgroups using a cluster analysis and also into those below (hypersensitive) and those within (normosensitive) the 95% confidence interval of the controls' mean for maximal tolerable distension (MTD). Results: Regardless of subgroup, the patients were distinguished from the controls by pain, bloating, straining and incomplete evacuation. Compared with controls, MTD was lower in the pain/bloating subgroup characterized by considerable pain and the bowel habit subgroup characterized by hard stools, variable stool consistency and heavily disturbed stool passage. Preprandial rectal hypersensitivity was highly prevalent in this bowel habit subgroup. No similar association with the pain/bloating subgroup was found. Patients and controls showed a significant and similar postprandial decrease in MTD. Conclusions: IBS is distinguished from health by pain, bloating, straining and a feeling of incomplete evcuation. Baseline rectal hypersensitivity is associated with constipation-like bowel habit. Increased rectal sensitivity after a meal and/or preceding distension is a normal reaction unimportant in the genesis of symptoms in IBS.     

Post-infectious irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder associated with abdominal pain or discomfort and altered bowel habits. The majority of patients describe an insidious onset of symptoms; however, a subset report a fairly precise time of onset following an attack of acute gastroenteritis. Typically, the potential acute infectious symptoms, such as fever and vomiting, resolve after several days, but abdominal discomfort, bloating, and diarrhea persist. Although the underlying mechanism of post-infectious IBS (PI-IBS) has not been established, ongoing inflammation appears to play a role, with an increase in serotonin-containing enterochromaffin cells, T lymphocytes, mast cells, proinflammatory cytokines, and intestinal permeability. Psychiatric comorbidities are less common in PI-IBS, compared with IBS patients in general; however, the prevalence of psychological disorders is still higher compared with that in the general population and is associated with a poorer prognosis. Overall, patients with PI-IBS have a slightly improved prognosis compared with those with IBS without an infectious onset.     

Pharmacologic and complementary and alternative medicine therapies for irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by episodic abdominal pain or discomfort in association with altered bowel habits (diarrhea and/or constipation). Other gastrointestinal symptoms, such as bloating and flatulence, are also common. A variety of factors are believed to play a role in the development of IBS symptoms, including altered bowel motility, visceral hypersensitivity, psychosocial stressors, altered brain-gut interactions, immune activation/low grade inflammation, alterations in the gut microbiome, and genetic factors. In the absence of biomarkers that can distinguish between IBS subgroups on the basis of pathophysiology, treatment of this condition is predicated upon a patient's most bothersome symptoms. In clinical trials, effective therapies have only offered a therapeutic gain over placebos of 7-15%. Evidence based therapies for the global symptoms of constipation predominant IBS (IBS-C) include lubiprostone and tegaserod; evidence based therapies for the global symptoms of diarrhea predominant IBS (IBS-D) include the probiotic Bifidobacter infantis, the nonabsorbable antibiotic rifaximin, and alosetron. Additionally, there is persuasive evidence to suggest that selected antispasmodics and antidepressants are of benefit for the treatment of abdominal pain in IBS patients. Finally, several emerging therapies with novel mechanisms of action are in development. Complementary and alternative medicine therapies including probiotics, herbal therapies and acupuncture are gaining popularity among IBS sufferers, although concerns regarding manufacturing standards and the paucity of high quality efficacy and safety data remain.     

A dose-ranging, phase II study of the efficacy and safety of alosetron in men with diarrhea-predominant IBS

BACKGROUND: A randomized, double blind, placebo-controlled dose-ranging study was conducted to assess the efficacy of alosetron in men with diarrhea-predominant irritable bowel syndrome (IBS). METHODS: Six hundred and sixty-two men were randomized to treatment with alosetron 0.5, 1.0, 2.0, 4.0 mg, or placebo twice daily for 12 wk, followed by a 4-wk posttreatment period. Adequate relief of IBS pain and discomfort during week 5-12 of the treatment phase was the primary endpoint; secondary endpoints included bowel urgency, stool frequency, and consistency, incomplete evacuation, bloating, and abdominal pain or discomfort. RESULTS: Subjects ranked urgency and abdominal pain as their most bothersome IBS symptoms. The average rate of adequate relief during week 5-12 was significantly higher in the alosetron 1.0 mg twice-daily group compared to placebo (53%vs 40%, p= 0.04), and all doses of alosetron significantly reduced stool consistency scores (p < 0.001) indicating firmer stools. No significant effects of alosetron were seen with regard to urgency, number of bowel movements, bloating, and incomplete evacuation. Constipation was the most common adverse event and occurred in a dose-related manner among subjects receiving alosetron, 9% (0.5 mg twice daily), 15% (1.0 mg twice daily), 11% (2.0 mg twice daily), and 21% (4.0 mg twice daily). No serious adverse events of constipation were reported. One subject in the 0.5 mg twice-daily group had an episode of rectal bleeding suggestive of a possible diagnosis of ischemic colitis. CONCLUSIONS: Alosetron 1 mg twice daily provided adequate relief of IBS pain and discomfort, and improved stool consistency in men with diarrhea-predominant IBS.     

Impaired transit and tolerance of intestinal gas in the irritable bowel syndrome

BACKGROUND: Patients with irritable bowel syndrome (IBS) frequently complain of excessive gas but their fasting volume of intestinal gas is apparently normal. We hypothesised that the pathophysiological mechanism involved may be impairment of intestinal gas transit. AIM: To investigate intestinal gas transit and tolerance in IBS patients compared with healthy subjects. METHODS: A gas mixture (N(2), O(2), and CO(2) in venous proportions) was infused into the jejunum of 20 patients with IBS and 20 healthy controls at 12 ml/min for four hours. Gas evacuation, initially flatus from the anus (two hours) and then intrarectally (two hours), was continuously recorded. Symptom perception (0-6 scale) and abdominal distension were measured at 10 minute intervals. RESULTS: After two hours of external gas (flatus) collection, 18 of 20 IBS patients had developed gas retention (>400 ml), increased gastrointestinal symptoms (score >3), or abdominal distension (>3 mm girth increment) compared with only four of 20 control subjects. During intrarectal gas collection, 13 of 17 patients still exhibited abnormal responses. CONCLUSION: A large proportion of patients with IBS can be shown to have impaired transit and tolerance of intestinal gas loads. This anomaly may represent a possible mechanism of IBS symptoms, specifically pain and bloating.