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

Effect of Iberogast (STW5) on tolerance to colonic gas in patients with irritable bowel syndrome: A randomized, double-blind, placebo control clinical trial

BACKGROUND

STW5 is an herbal medicinal product that, in previous studies, reduced abdominal pain in irritable bowel syndrome (IBS). The effect of STW5 on gas-related abdominal symptoms is unknown.

AIM

To determine the effects of STW5, compared to placebo, on the responses to colonic gas in IBS.

METHODS

Using a cross-over design, two gas challenge tests were performed in 10 patients with IBS and bloating after 2-weeks treatment with (a) STW5 and (b) placebo. The challenge test consisted in continuous infusion of gas into the colon (24 mL/min for 60 min), followed by a 30-min free evacuation period. Gas evacuation, symptom perception, and abdominal distension were continuously registered.

RESULTS

Colonic gas filling was associated to a significant rise in abdominal symptom perception, that was significantly greater when patients were on-placebo (score increment 4.0 ± 0.3) compared with on-STW5 (score increment 3.2 ± 0.4; p = 0.035). Gas filling was associated to a progressive abdominal distension that was similar with both treatments. Opening of the rectal cannula produced a massive gas evacuation, similar after both treatments, associated to a return of abdominal perception and distension to basal levels when patients were on-STW5 (score increment -0.1 ± 0.4; distension 0.3 ± 0.2 cm; p = 0.399, and p = 0.112 vs. basal), whereas both remained increased on-placebo (score increment 0.5 ± 0.3; distension 0.8 ± 0.3 cm; p = 0.048, and p = 0.016 vs. infusion start).

CONCLUSIONS

STW5 improves colonic gas tolerance in IBS patients with bloating without a significant effect on gas retention and evacuation. This medicinal product can be beneficious for treatment of gas-related abdominal symptoms in patients with bloating. EudraCT: 2019-003976-38.

Visible abdominal distension in functional gut disorders: Objective evaluation

BACKGROUND

Visible abdominal distension has been attributed to: (A) distorted perception, (B) intestinal gas accumulation, or (C) abdominophrenic dyssynergia (diaphragmatic push and anterior wall relaxation).

METHODS

A pool of consecutive patients with functional gut disorders and visible abdominal distension included in previous studies (n = 139) was analyzed. Patients (61 functional bloating, 74 constipation-predominant irritable bowel syndrome and 4 with alternating bowel habit) were evaluated twice, under basal conditions and during a self-reported episode of visible abdominal distension; static abdominal CT images were taken in 104 patients, and dynamic EMG recordings of the abdominal walls in 76, with diaphragmatic activity valid for analysis in 35.

KEY RESULTS

(A) Objective evidence of abdominal distension was obtained by tape measure (increase in girth in 138 of 139 patients), by CT imaging (increased abdominal perimeter in 96 of 104 patients) and by abdominal EMG (reduced activity, i.e., relaxation, in 73 of 76 patients). (B) Intestinal gas volume was within ±300 ml from the basal value in 99 patients, and above in 5 patients, who nevertheless exhibited a diaphragmatic descent. (C) Diaphragmatic contraction was detected in 34 of 35 patients by EMG (increased activity) and in 82 of 103 patients by CT (diaphragmatic descent).

CONCLUSIONS AND INFERENCES

In most patients complaining of episodes of visible abdominal distention: (A) the subjective claim is substantiated by objective evidence; (B) an increase in intestinal gas does not justify visible abdominal distention; (C) abdominophrenic dyssynergia is consistently evidenced by dynamic EMG recording, but static CT imaging has less sensitivity.

Effect of Resistant Dextrin on Intestinal Gas Homeostasis and Microbiota

Previous studies have shown that a resistant dextrin soluble fibre has prebiotic properties with related health benefits on blood glucose management and satiety. Our aim was to demonstrate the effects of continuous administration of resistant dextrin on intestinal gas production, digestive sensations, and gut microbiota metabolism and composition. Healthy subjects (n = 20) were given resistant dextrin (14 g/d NUTRIOSE^®, Roquette Frères, Lestrem, France) for four weeks. Outcomes were measured before, at the beginning, end, and two weeks after administration: anal evacuations of gas during daytime; digestive perception, girth, and gas production in response to a standard meal; sensory and digestive responses to a comfort meal; volume of colonic biomass by magnetic resonance; taxonomy and metabolic functions of fecal microbiota by shotgun sequencing; metabolomics in urine. Dextrin administration produced an initial increase in intestinal gas production and gas-related sensations, followed by a subsequent decrease, which magnified after discontinuation. Dextrin enlarged the volume of colonic biomass, inducing changes in microbial metabolism and composition with an increase in short chain fatty acids-producing species and modulation of bile acids and biotin metabolism. These data indicate that consumption of a soluble fibre induces an adaptative response of gut microbiota towards fermentative pathways with lower gas production.

Assessment of gastrointestinal function and its' effect on bone mineral density and body composition in hypermobility spectrum disorder and hypermobile Ehlers-Danlos syndrome

BACKGROUND

Hypermobile Ehlers-Danlos Syndrome (hEDS) and Hypermobility Spectrum Disorders (HSD) are associated with hypermobility, musculoskeletal pain, a decreased bone mineral density (BMD) and gastrointestinal (GI) complications. The role of GI symptoms and diet in BMD has not been established in this population. The GI complications can lead to an energy deficit due to lack of essential macronutrients. The primary objective of this study was to determine the severity of GI symptoms compared to body composition and BMD in individuals with hEDS/HSD. The secondary objective is to examine GI symptoms on energy balance, body composition and strength.

METHODOLOGY

This study was IRB approved. Eighteen female participants (aged 28.2 ± 4.9; BMI 22.5 ± 4.9) with a diagnosis of hEDS or HSD and 18 female healthy control participants (aged 28.1 ± 3.8; BMI 22.8 ±3.9) signed consent to participate. Participants were matched by sex, age, and BMI. The Gastrointestinal Symptom Rating Scale (GSRS) was used to investigate severity of GI symptoms. Dual X-ray absorptiometry was used to determine body composition (body fat%, lean body mass (LBM). BMD was measured by Z- scores of both femurs and lumbar spine. Resting metabolic rate (RMR) was measured using indirect calorimetry and strength was determined using a hand grip dynamometer.

RESULTS

All hEDS/HSD participants reported GI symptoms. There was no difference in body composition between hEDS/HSD and controls. Participants with hEDS/HSD had lower BMD both femoral z scores (p=0.02,0.004) and spine z scores (p= 0.04). There was no difference in caloric intake between groups; yet both groups demonstrated caloric deficits. Additionally, hEDS/HSD consumed less protein and more carbohydrates (p=0.03, p=0.03). There were no differences in grip strength.

CONCLUSIONS

This study identified that pre-menopausal women with hEDS/HSD presented with significant GI complications and lower BMD than age matched controls. The GI complications and the reduced protein intake long-term may have a lasting impact on bone health. This study found that the GSRS identified and quantified GI symptoms in persons with hEDS/HSD. Future studies are needed for the longitudinal effects of a caloric/protein deficit in this population and to help guide future preventive and nutritional treatment approaches in individuals with hEDS/HSD.

Management of bloating

Abdominal bloating is a subjective sensation of trapped abdominal gas, producing abdominal pressure, fullness sensation, and, in some patients, associated objective abdominal distension. In this month's edition of the journal, a new validated questionnaire to assess the prevalence and impact of gas-related symptoms is presented by Duracinsky et al., showing that gas-related abdominal symptoms are prevalent in patients with irritable bowel syndrome and have a measurable impact on patients daily life. A parallel study by Gardiner et al. assessing the severity of bloating in functional gastrointestinal disorders shows that severe bloating is associated with the severity of abdominal pain, constipation, and somatization, advancing our understanding of the clinical characteristics and relevance of gas-related symptoms in the broad spectrum of functional gastrointestinal disorders. Management of bloating includes non-pharmacological and pharmacological strategies. Dietary interventions to reduce intestinal fermentation and ingestion of food supplements like prebiotics or probiotics can reduce bloating by reducing gas production. The main targets of pharmacological treatments are to improve transit and evacuation with prokinetics, to improve intestinal gas tolerance with antispasmodics and/or neuromodulators, and to modify intestinal microbiota with antibiotics. Secretagogues act by increasing intestinal secretion and decreasing visceral sensitivity and have been reported to be an effective treatment alternative for patients with bloating associated with constipation. Biofeedback therapy addressed to correct abdomino-phrenic dysynergia may be useful for patients with objective abdominal distension, and patients with bloating associated with outlet obstructed defecation may benefit from anorectal biofeedback.

Abdominothoracic Postural Tone Influences the Sensations Induced by Meal Ingestion

Postprandial objective abdominal distention is frequently associated with a subjective sensation of abdominal bloating, but the relation between both complaints is unknown. While the bloating sensation has a visceral origin, abdominal distention is a behavioral somatic response, involving contraction and descent of the diaphragm with protrusion of the anterior abdominal wall. Our aim was to determine whether abdominal distention influences digestive sensations. In 16 healthy women we investigated the effect of intentional abdominal distention on experimentally induced bloating sensation (by a meal overload). Participants were first taught to produce diaphragmatic contraction and visible abdominal distention. After a meal overload, sensations of bloating (0 to 10) and digestive well-being (-5 to + 5) were measured during 30-s. maneuvers alternating diaphragmatic contraction and diaphragmatic relaxation. Compared to diaphragmatic relaxation, diaphragmatic contraction was associated with diaphragmatic descent (by 21 + 3 mm; p < 0.001), objective abdominal distension (32 + 5 mm girth increase; p = 0.001), more intense sensation of bloating (7.3 + 0.4 vs. 8.0 + 0.4 score; p = 0.010) and lower digestive well-being (-0.9 + 0.5 vs. -1.9 + 0.5 score; p = 0.028). These results indicate that somatic postural tone underlying abdominal distention worsens the perception of visceral sensations (ClinicalTrials.gov ID: NCT04691882).

Responses to gastric gas in patients with functional gastrointestinal disorders

BACKGROUND

Gas-related abdominal symptoms are common in patients with functional gut disorders, but the responses to cope with the large volumes of gas that enter daily into the stomach have not been studied in detail. Our aim was to evaluate transit and tolerance of gastric gas in patients with functional gastrointestinal disorders.

METHODS

In eight healthy volunteers and 24 patients with functional gut disorders (eight functional dyspepsia, eight belching disorder, and eight functional bloating) 1500 ml of a gas mixture were infused into the stomach at 25 ml/min. Belching, rectal gas evacuation, and abdominal perception were continuously recorded for 90 minutes.

KEY RESULTS

Healthy subjects expelled the infused gas per rectum (1614 ± 73 ml), with a small rise in epigastric perception (score increment 1.0 ± 0.4) and virtually no belching (1 ± 1 belches). Patients with functional dyspepsia had a hypersensitive response to gastric gas, with a significant rise in epigastric perception (score increment 2.5 ± 0.6; P = .045), a transient delay in rectal gas evacuation and similar belching as healthy controls. Patients with belching disorders responded to gastric gas with continuous belches (33 ± 13 belches; P = .002), low epigastric perception, and a small reduction in rectal gas evacuation. Patients with functional bloating exhibited a slow transit response, with reduced rectal gas evacuation (1017 ± 145 ml; P = .002) and abdominal symptoms (score increment 2.5 ± 0.7), but without compensatory belching.

CONCLUSIONS AND INFERENCES

Different pathophysiological mechanisms underlay specific adaptive responses to gastric gas in patients with different functional gut disorders. Therapeutic interventions for gas-related abdominal symptoms should be addressed towards these specific pathophysiological disturbances.

Abdominal distension after eating lettuce: The role of intestinal gas evaluated in vitro and by abdominal CT imaging

BACKGROUND

Some patients complain that eating lettuce, gives them gas and abdominal distention. Our aim was to determine to what extent the patients' assertion is sustained by evidence.

METHODS

An in vitro study measured the amount of gas produced during the process of fermentation by a preparation of human colonic microbiota (n = 3) of predigested lettuce, as compared to beans, a high gas-releasing substrate, to meat, a low gas-releasing substrate, and to a nutrient-free negative control. A clinical study in patients complaining of abdominal distention after eating lettuce (n = 12) measured the amount of intestinal gas and the morphometric configuration of the abdominal cavity in abdominal CT scans during an episode of lettuce-induced distension as compared to basal conditions.

KEY RESULTS

Gas production by microbiota fermentation of lettuce in vitro was similar to that of meat (P = .44), lower than that of beans (by 78 ± 15%; P < .001) and higher than with the nutrient-free control (by 25 ± 19%; P = .05). Patients complaining of abdominal distension after eating lettuce exhibited an increase in girth (35 ± 3 mm larger than basal; P < .001) without significant increase in colonic gas content (39 ± 4 mL increase; P = .071); abdominal distension was related to a descent of the diaphragm (by 7 ± 3 mm; P = .027) with redistribution of normal abdominal contents.

CONCLUSION AND INFERENCES

Lettuce is a low gas-releasing substrate for microbiota fermentation and lettuce-induced abdominal distension is produced by an uncoordinated activity of the abdominal walls. Correction of the somatic response might be more effective than the current dietary restriction strategy.

How much bloating in the irritable bowel syndrome?

The irritable bowel syndrome (IBS) is the most common chronic gastrointestinal disorder referred to gastroenterologists. One of the most common manifestations of IBS is bloating. Abdominal bloating is defined as subjective sensation of abdominal distension associated with girth increment. Therefore, it is described in the Rome IV criteria as bloating/abdominal distension. Bloating symptoms are reported by 10-30% of the general population and it was rated as the most bothersome symptom by 60% of IBS patients; the lack of specificity of this complaint prevented bloating to be included between the diagnostic criteria for IBS. Indeed, bloating may be reported also in healthy people or in other functional conditions. This paper looks to the evolutions of the concepts on bloating according to the Rome working groups from the beginning until now and it represents a comprehensive review on the prevalence and pathogenesis of bloating.

Nutrient drink test: A promising new tool for irritable bowel syndrome diagnosis

BACKGROUND

Irritable bowel syndrome (IBS) is a highly prevalent condition. It is diagnosed on the basis of chronic symptoms after the clinical and/or investigative exclusion of organic diseases that can cause similar symptoms. There is no reproducible non-invasive test for the diagnosis of IBS, and this raises diagnostic uncertainty among physicians and hinders acceptance of the diagnosis by patients. Functional gastrointestinal (GI) syndromes often present with overlapping upper and lower GI tract symptoms, now believed to be generated by visceral hypersensitivity. This study examines the possibility that, in IBS, a nutrient drink test (NDT) provokes GI symptoms that allow a positive differentiation of these patients from healthy subjects.

AIM

To evaluate the NDT for the diagnosis of IBS.

METHODS

This prospective case-control study compared the effect of two different nutrient drinks on GI symptoms in 10 IBS patients (patients) and 10 healthy controls (controls). The 500 kcal high nutrient drink and the low nutrient 250 kcal drink were given in randomized order on separate days. Symptoms were assessed just before and at several time points after drink ingestion. Global dyspepsia and abdominal scores were derived from individual symptom data recorded by two questionnaires designed by our group, the upper and the general GI symptom questionnaires, respectively. Psycho-social morbidity and quality of life were also formally assessed. The scores of patients and controls were compared using single factor analysis of variance test.

RESULTS

At baseline, IBS patients compared to controls had significantly higher levels of GI symptoms such as gastro-esophageal reflux (P = 0.05), abdominal pain (P = 0.001), dyspepsia (P = 0.001), diarrhea (P = 0.001), and constipation (P = 0.001) as well as higher psycho-social morbidity and lower quality of life. The very low incidence of GI symptoms reported by control subjects did not differ significantly for the two test drinks. Compared with the low nutrient drink, IBS patients with the high nutrient drink had significantly more dyspeptic symptoms at 30 (P = 0.014), 45 (P = 0.002), 60 (P = 0.001), and 120 min (P = 0.011). Dyspeptic symptoms triggered by the high nutrient drink during the first 120 min gave the best differentiation between healthy controls and patients (area under receiver operating curve of 0.915 at 45 min for the dyspepsia score). Continued symptom monitoring for 24 h did not enhance separation of patients from controls.

CONCLUSION

A high NDT merits further evaluation as a diagnostic tool for IBS.

Gastric gas dynamics in healthy humans

BACKGROUND

To cope with the daily increments of gastric gas, the stomach can propel gas to the small bowel or trigger the belching reflex. Our aim was to evaluate transit of free gastric gas in healthy humans, and its relationship with abdominal symptoms.

METHODS

In 24 healthy volunteers a gas mixture was infused into the stomach at 0 mL/min (sham infusion), 25 mL/min, 50 mL/min, and 100 mL/min (n = 6 each) up to 1500 mL. Belching, rectal gas evacuation, and abdominal perception were continuously recorded for 90 min.

KEY RESULTS

Sham infusion was associated to low rectal gas evacuation (187 ± 94 mL after 90 min), and belching (0 ± 0). In contrast, gastric gas infusion increased rectal gas evacuation (1198 ± 176 mL; P = .025) and belching (4 ± 1 belches; P = .0520) without differences between the infusion rates tested. Overall, there was a negative correlation between rectal gas evacuation and belching (r = -.72; P < .0001): 6 subjects had frequent belching (14 ± 2 belches) and minor rectal gas evacuation (330 ± 112 mL), whereas 12 subjects had virtually no belches (1 ± 1 belches) and greater rectal gas evacuation (1630 ± 147 mL; P < .001 vs belchers for both). Gas infusion induced lower abdominal symptoms in belchers (score increment 0.7 ± 0.3) than in rectal gas evacuators (score increment 1.7 ± 0.5; P = .033).

CONCLUSIONS AND INFERENCES

An excellent balance between belching and distal gastric empting allows the stomach to adapt to great variations in gas intake. In general, most gastric gas is emptied to distal intestinal segments, but in some circumstances gastric gas induces belching, a mechanism that may improve gas tolerance.

Clinical and symptom scores are significantly correlated with fecal microbiota features in patients with symptomatic uncomplicated diverticular disease: a pilot study

BACKGROUND

There is growing consensus that symptomatic uncomplicated diverticular disease is a chronic inflammatory condition, and that alterations in the fecal microbiota may contribute to its pathogenesis.

OBJECTIVE

The aim of this study was to relate the fecal microbiota composition in symptomatic uncomplicated diverticular disease to measures of inflammation, symptoms, and history of previous acute diverticulitis.

PARTICIPANTS AND METHODS

Fecal microbiota composition in 28 individuals with symptomatic uncomplicated diverticular disease was characterized by 16S RNA gene amplicon sequencing. Microbiota composition was related to clinical history, symptom and inflammation measures, and demographic variables.

RESULTS

Previous acute diverticulitis was associated with higher relative abundance of Pseudobutyrivibrio, Bifidobacterium, Christensenellaceae family, and Mollicutes RF9 order (P=0.004, 0.006, 0.010, and 0.019, respectively), but not microbiota alpha or beta diversity. A higher bloating severity score was significantly correlated with a higher relative abundance of Ruminococcus (P=0.032), and significantly inversely correlated with the relative abundance of the Roseburia (P=0.002). Fecal calprotectin levels were positively correlated with alpha diversity (Shannon index, P=0.005) and the relative abundance of Lactobacillus (P=0.004). Pain score was positively correlated with the relative abundance of Cyanobacterium (adjusted P=0.032).

CONCLUSION

Patient symptoms in symptomatic diverticular disease are significantly correlated with features of the fecal microbiota. Our findings suggest the potential utility of therapies that target intestinal microbiology, such as dietary prebiotic supplements.

Correction of Abdominal Distention by Biofeedback-Guided Control of Abdominothoracic Muscular Activity in a Randomized, Placebo-Controlled Trial

BACKGROUND & AIMS

Abdominal distention is produced by abnormal somatic postural tone. We developed an original biofeedback technique based on electromyography-guided control of abdominothoracic muscular activity. We performed a randomized, placebo-controlled study to demonstrate the superiority of biofeedback to placebo for the treatment of abdominal distention.

METHODS

At a referral center in Spain, we enrolled consecutive patients with visible abdominal distention who fulfilled the Rome III criteria for functional intestinal disorders (47 women, 1 man; 21-74 years old); 2 patients assigned to the placebo group withdrew and 2 patients assigned to biofeedback were not valid for analysis. Abdominothoracic muscle activity was recorded by electromyography. The patients in the biofeedback group were shown the signal and instructed to control muscle activity, whereas patients in the placebo received no instructions and were given oral simethicone. Each patient underwent 3 sessions over a 10-day period. The primary outcomes were subjective sensation of abdominal distention, measured by graphic rating scales for 10 consecutive days before and after the intervention.

RESULTS

Patients in the biofeedback group effectively learned to reduce intercostal activity (by a mean 45% ± 3%), but not patients in the placebo group (reduced by a mean 5% ± 2%; P < .001). Patients in the biofeedback group learned to increase anterior wall muscle activity (by a mean 101% ± 10%), but not in the placebo group (decreased by a mean 4% ± 2%; P < .001). Biofeedback resulted in a 56% ± 1% reduction of abdominal distention (from a mean score of 4.6 ± 0.2 to 2.0 ± 0.2), whereas patients in the placebo group had a reduction of only 13% ± 8% (from a mean score of 4.7 ± 0.1 to 4.1 ± 0.4) (P < .001).

CONCLUSIONS

In a randomized trial of patients with a functional intestinal disorder, we found that abdominal distention can be effectively corrected by biofeedback-guided control of abdominothoracic muscular activity, compared with placebo. ClincialTrials.gov no: NCT01205100.

Colonic gas homeostasis: Mechanisms of adaptation following HOST-G904 galactooligosaccharide use in humans

BACKGROUND

We have shown that a galactooligosaccharide prebiotic administration (HOST-G904) initially increased intestinal gas production and this increase declined back to baseline after 2 week administration. Our aim was to determine the mechanism of microbiota adaptation; i.e., to determine whether the net reduction is due to decreased overall production or increased gas consumption.

METHODS

In 10 healthy subjects, intestinal gas production and intraluminal disposal was measured before, at the beginning and after 2 week of HOST-G904 prebiotic administration. Anal gas was collected for 4 hour after a probe meal. Paired studies were performed without and with high-rate infusion of exogenous gas (24 mL/min) into the jejunum to wash-out the endogenous gas produced by bacterial fermentation. The exogenous gas infused was labeled (5% SF₆ ) to calculate the proportion of endogenous gas evacuated.

KEY RESULTS

The volume of intestinal gas produced i.e., endogenous gas washed-out, increased by 37% at the beginning of HOST-G904 administration (P=.049 vs preadministration) and decreased down to preadministration level after 2 week administration (P=.030 vs early administration). The proportion of gas eliminated from the lumen before reaching the anus tended to increase after 2-week administration (87±3% vs 78±5% preadministration; P=.098).

CONCLUSIONS & INFERENCES

Adaptation to regular consumption of HOST-G904 prebiotic involves a shift in microbiota metabolism toward low-gas producing pathways, with a non-significant increase in gas-consuming activity. Hence, regular consumption of HOST-G904 regulates intestinal gas metabolism: less gas is produced and a somewhat larger proportion of it is consumed.

Effect of prucalopride on intestinal gas tolerance in patients with functional bowel disorders and constipation

BACKGROUND AND AIM

Patients with functional bowel disorders develop gas retention and symptoms in response to intestinal gas loads that are well tolerated by healthy subjects. Stimulation of 5HT-4 receptors in the gut has both prokinetic and antinociceptive effects. The aim of this study is to determine the effect of prucalopride, a highly selective 5HT-4 agonist, on gas transit and tolerance in women with functional bowel disorders complaining of constipation.

METHODS

Twenty-four women with functional bowel disorders complaining of constipation were included in the study. Patients were studied twice on separate days in a cross-over design. On each study day, an intestinal gas challenge test was performed. During the five previous days, prucalopride (2 mg/day) or placebo was administered. Abdominal symptoms, stool frequency, and stool consistency were recorded during the treatment period on daily questionnaires.

RESULTS

During the gas challenge test, prucalopride did not decrease the volume of gas retained in the subset of patients who had significant gas retention (≥ 200 mL) while on placebo. However, in those patients who had increased symptoms during the gas test (≥ 3 on a 0 to 6 scale) when on placebo, prucalopride did significantly reduce the perception of symptoms (2.3 ± 0.5 mean score vs 3.5 ± 0.3 on placebo; P = 0.045). During the treatment period with prucalopride, patients exhibited an increase in the total number of bowel movements and decreased stool consistency compared with placebo.

CONCLUSION

Prucalopride reduces abdominal symptoms without modifying gas retention when patients with functional bowel disorders are challenged with the gas transit and tolerance test. European Clinical Trials Database (EudraCT2011-006354-86).

Effect of Chicory-derived Inulin on Abdominal Sensations and Bowel Motor Function

GOAL

To determine the effect of a prebiotic chicory-derived inulin-type fructan on the tolerance of intestinal gas.

BACKGROUND

Subjects with gas-related complaints exhibit impaired handling of intestinal gas loads and we hypothesized that inulin would have a beneficial effect.

STUDY

Placebo-controlled, parallel, randomized, double-blind trial. Subjects with abdominal symptoms and reduced tolerance of intestinal gas (selected by a pretest) received either inulin (8 g/d, n=18) or maltodextrin as a placebo (8 g/d, n=18) for 4 weeks. A gas challenge test (4 h jejunal gas infusion at 12 mL/min while measuring abdominal symptoms and gas retention for 3 h) was performed before and at the end of the intervention phase. Gastrointestinal symptoms and bowel habits (using daily questionnaires for 1 wk) and fecal bifidobacteria counts were measured before and at the end of the intervention.

RESULTS

Inulin decreased gas retention during the gas challenge test (by 22%; P=0.035 vs. baseline), while the placebo did not, but the intergroup difference was not statistically significant (P=0.343). Inulin and placebo reduced the perception of abdominal sensations in the gas challenge test to a similar extent (by 52% and 43%, respectively). Participants reported moderate gastrointestinal symptoms and normal bowel habits during baseline examination, and these findings remained unchanged in both groups during the intervention. Inulin led to a higher relative abundance of bifidobacteria counts (P=0.01 vs. placebo).

CONCLUSIONS

A daily dose of inulin that promotes bifidobacteria growth and may improve gut function, is well tolerated by subjects with gastrointestinal complaints.

Diet in irritable bowel syndrome: What to recommend, not what to forbid to patients!

A substantial proportion of patients with irritable bowel syndrome (IBS) associate their symptoms with the ingestion of specific foods. Therefore, in recent years, scientific research has increasingly focused on the role of diet in IBS and dietary management is now considered an important tool in IBS treatment. This article reviews the main dietary approaches in IBS emphasizing evidence from experimental and observational studies and summarizing the main diet and lifestyle recommendations provided by dietary guidelines and scientific literature. Despite the limited evidence for a beneficial role, general advice on healthy eating and lifestyle is recommended as the first-line approach in the dietary management of IBS. Standard recommendations include adhering to a regular meal pattern, reducing intake of insoluble fibers, alcohol, caffeine, spicy foods, and fat, as well as performing regular physical activity and ensuring a good hydration. Second-line dietary approach should be considered where IBS symptoms persist and recommendations include following a low FODMAP diet, to be delivered only by a healthcare professional with expertise in dietary management. The efficacy of this diet is supported by a growing body of evidence. In contrast, the role of lactose or gluten dietary restriction in the treatment of IBS remains subject to ongoing research with a lack of high-quality evidence. Likewise, further clinical trials are needed to conclude the efficacy of probiotics on IBS symptoms.

Metabolic adaptation of colonic microbiota to galactooligosaccharides: a proof-of-concept-study

BACKGROUND

Prebiotics have been shown to reduce abdominal symptoms in patients with functional gut disorders, despite that they are fermented by colonic bacteria and may induce gas-related symptoms.

AIM

To investigate changes in the metabolic activity of gut microbiota induced by a recognised prebiotic.

METHODS

Healthy subjects (n = 20) were given a prebiotic (2.8 g/day HOST-G904, HOST Therabiomics, Jersey, Channel Islands) for 3 weeks. During 3-day periods immediately before, at the beginning and at the end of the administration subjects were put on a standard diet (low fibre diet supplemented with one portion of high fibre foods) and the following outcomes were measured: (i) number of daytime gas evacuations for 2 days by means of an event marker; (ii) volume of gas evacuated via a rectal tube during 4 h after a test meal; and (iii) microbiota composition by faecal Illumina MiSeq sequencing.

RESULTS

At the beginning of administration, HOST-G904 significantly increased the number of daily anal gas evacuations (18 ± 2 vs. 12 ± 1 pre-administration; P < 0.001) and the volume of gas evacuated after the test meal (236 ± 23 mL vs. 160 ± 17 mL pre-administration; P = 0.006). However, after 3 weeks of administration, these effects diminished (11 ± 2 daily evacuations, 169 ± 23 mL gas evacuation). At day 21, relative abundance of butyrate producers (Lachnospiraceae) correlated inversely with the volume of gas evacuated (r = -0.52; P = 0.02).

CONCLUSION

The availability of substrates induces an adaptation of the colonic microbiota activity in bacterial metabolism, which produces less gas and associated issues. Clinical trials.gov NCT02618239.

Colonic content: effect of diet, meals, and defecation

BACKGROUND

The metabolic activity of colonic microbiota is influenced by diet; however, the relationship between metabolism and colonic content is not known. Our aim was to determine the effect of meals, defecation, and diet on colonic content.

METHODS

In 10 healthy subjects, two abdominal MRI scans were acquired during fasting, 1 week apart, and after 3 days on low- and high-residue diets, respectively. With each diet, daily fecal output and the number of daytime anal gas evacuations were measured. On the first study day, a second scan was acquired 4 hours after a test meal (n=6) or after 4 hours with nil ingestion (n=4). On the second study day, a scan was also acquired after a spontaneous bowel movement.

RESULTS

On the low-residue diet, daily fecal volume averaged 145 ± 15 mL; subjects passed 10.6 ± 1.6 daytime anal gas evacuations and, by the third day, non-gaseous colonic content was 479 ± 36 mL. The high-residue diet increased the three parameters to 16.5 ± 2.9 anal gas evacuations, 223 ± 19 mL fecal output, and 616 ± 55 mL non-gaseous colonic content (P<.05 vs low-residue diet for all). On the low-residue diet, non-gaseous content in the right colon had increased by 41 ± 11 mL, 4 hours after the test meal, whereas no significant change was observed after 4-hour fast (-15 ± 8 mL; P=.006 vs fed). Defecation significantly reduced the non-gaseous content in distal colonic segments.

CONCLUSION & INFERENCES

Colonic content exhibits physiologic variations with an approximate 1/3 daily turnover produced by meals and defecation, superimposed over diet-related day-to-day variations.

Abdominal bloating and irritable bowel syndrome like symptoms following microinstillation inhalation exposure to chemical warfare nerve agent VX in guinea pigs

While assessing the methylphosphonothioic acid S-(2-(bis(1-methylethyl)amino)ethyl)O-ethyl ester (VX) induced respiratory toxicity and evaluating therapeutics against lung injury, we observed that the animals were experiencing abnormal swelling in the abdominal area. Nerve agent has been known to increase salivary, nasal and gastrointestinal secretion and cause diarrhea. This study was initiated to investigate the effect of VX on the gastrointestinal tract (GI) since abdominal pathology may affect breathing and contribute to the on going respiratory toxicity. The mid-abdominal diameter and the size of the lower left abdomen was measured before and after 27.3 mg/m3 VX exposure by microinstillation and at 30min intervals up to 2h post-VX exposure. Both VX and saline exposed animals exhibited a decrease in circumference of the upper abdomen, although the decrease was slightly higher in VX-exposed animals up to 1 h. The waist diameter increased slightly in VX-exposed animals from 60 to 90min post-VX exposure but was similar to saline controls. The lower left abdomen near to the cecum, 6 cm below and 2 cm to the right of the end of the sternum, showed an increase in size at 30—60 min that was significantly increased at 90—120 min post-VX exposure. In addition, VX-exposed animals showed loose fecal matter compared to controls. Necropsy at 24 h showed an increased small intestine twisting motility in VX-exposed animals. Body tissue AChE assay showed high inhibition in the esophagus and intestine in VX-exposed animals indicating that a significant amount of the agent is localized to the GI following microinstillation exposure. These results suggest that microinstillation inhalation VX exposure induces gastrointestinal disturbances similar to that of irritable bowel syndrome and bloating.

Prevalence and treatment of small intestinal bacterial overgrowth in postoperative patients with colorectal cancer

To investigate the prevalence of small intestinal bacterial overgrowth (SIBO) in patients with colorectal cancer (CRC) after surgical treatment and observe whether gastrointestinal symptoms may improve with rifaximin, 43 postoperative CRC patients (CRC group) and 30 healthy individuals (normal group) were subjected to the glucose hydrogen breath test (GHBT). All the patients were asked to evaluate the gastrointestinal symptoms using the visual analogue scale (VAS). SIBO-positive patients were administered rifaximin for 10 days on the basis of the original treatment. After the treatment, the patients were asked to undergo GHBT and re-evaluate the gastrointestinal symptoms score (GISS). The results demonstrated that 18 of the 43 postoperative patients with CRC were SIBO-positive (41.86%), which was significantly higher compared with the incidence in normal controls (6.67%) (P<0.05). GISS was higher in SIBO-positive patients (P<0.05). Following rifaximin treatment, 6 of the 18 (33.33%) SIBO-positive patients had improved, as evaluated by GHBT and VAS. Additionally, the GISS in the SIBO-turned-negative group had improved significantly compared with that in the non-turned-negative group (P<0.05). The symptoms of all 18 SIBO-positive patients following rifaximin treatment improved notably, particularly diarrhea (P<0.05). In conclusion, postoperative CRC patients are more likely to develop SIBO compared with healthy individuals, and SIBO may aggravate digestive symptoms. The administration of rifaximin improved the overall gastrointestinal symptoms, particularly diarrhea, in SIBO-positive patients.

Effect of selective CCK1 receptor antagonism on accommodation and tolerance of intestinal gas in functional gut disorders

BACKGROUND

Participants with functional gut disorders develop gas retention and symptoms in response to intestinal gas loads that are well tolerated by healthy subjects. To determine the role of cholecystokinin (CCK1 ) receptors on gas transit and tolerance in women with functional gut disorders.

METHODS

In 12 healthy women, and 24 women with functional gut disorders (12 dyspepsia and 12 constipation-predominant irritable bowel syndrome) gas was infused into the jejunum at 12 mL/min for 3 h with simultaneous duodenal lipid infusion (intralipid 1 kcal/min), while measuring anal gas evacuation and abdominal symptoms on a 0-6 score scale. Triple-blind paired studies during iv infusion of dexloxiglumide (2.5 mg/kg bolus plus 5 mg/kg h continuous infusion), a selective CCK1 inhibitor, or saline (control) were performed in random order.

RESULTS

During saline infusion participants with functional gut disorders developed significantly greater gas retention and abdominal symptoms than healthy subjects (394 ± 40 mL vs 265 ± 35 mL and 2.8 ± 0.3 vs 1.9 ± 0.4 highest abdominal symptom score, respectively; P < 0.05 for both). Dexloxiglumide increased gas retention in both groups (514 ± 35 mL and 439 ± 60 mL, respectively; P = 0.033 vs saline for both); however, despite the larger retention, dexloxiglumide reduced abdominal symptoms (2.3 ± 0.2 score and 0.8 ± 0.3 score, respectively; P = 0.05 vs saline for both). Post-hoc analysis showed that, the decrease in abdominal symptoms was more pronounced in those participants with functional gut disorders with higher basal abdominal symptoms than in the rest (P = 0.037).

CONCLUSION

Inhibition of CCK1 receptors by dexloxiglumide increases intestinal gas retention and reduces abdominal symptoms in response to by intestinal gas loads. European Clinical Trials Database (EudraCT 2005-003338-16).

Accumulative effect of food residues on intestinal gas production

BACKGROUND

As mean transit time in the colon is longer than the interval between meals, several consecutive meal loads accumulate, and contribute to colonic biomass. Our aim was to determine the summation effect of fermentable food residues on intestinal gas production.

METHODS

In eight healthy subjects, the volume of endogenous intestinal gas produced in the intestine over a 4-h period was measured by means of a wash-out technique, using an exogenous gas infusion into the jejunum (24 mL/min) and collection of the effluent via a rectal Foley catheter. The exogenous gas infused was labeled (5% SF6 ) to calculate the proportion of endogenous intestinal gas evacuated. In each subject, four experiments were performed ≥1 week apart combining a 1-day high- or low-flatulogenic diet with a test meal or fast.

KEY RESULTS

Basal conditions: on the low-flatulogenic diet, intestinal gas production during fasting over the 4-h study period was 609 ± 63 mL. Effect of diet: during fasting, intestinal gas production on the high-flatulogenic diet was 370 ± 146 mL greater than on the low-flatulogenic diet (p = 0.040). Effect of test meal: on the low-flatulogenic diet, intestinal gas production after the test meal was 681 ± 114 mL greater than during fasting (p = 0.001); a similar effect was observed on the high-flatulogenic diet (599 ± 174 mL more intestinal gas production after the test meal than during fasting; p = 0.021).

CONCLUSIONS & INFERENCES

Our data demonstrate temporal summation effects of food residues on intestinal gas production. Hence, intestinal gas production depends on pre-existing and on recent colonic loads of fermentable foodstuffs.

Intestinal gas content and distribution in health and in patients with functional gut symptoms

BACKGROUND

The precise relation of intestinal gas to symptoms, particularly abdominal bloating and distension remains incompletely elucidated. Our aim was to define the normal values of intestinal gas volume and distribution and to identify abnormalities in relation to functional-type symptoms.

METHODS

Abdominal computed tomography scans were evaluated in healthy subjects (n = 37) and in patients in three conditions: basal (when they were feeling well; n = 88), during an episode of abdominal distension (n = 82) and after a challenge diet (n = 24). Intestinal gas content and distribution were measured by an original analysis program. Identification of patients outside the normal range was performed by machine learning techniques (one-class classifier). Results are expressed as median (IQR) or mean ± SE, as appropriate.

KEY RESULTS

In healthy subjects the gut contained 95 (71, 141) mL gas distributed along the entire lumen. No differences were detected between patients studied under asymptomatic basal conditions and healthy subjects. However, either during a spontaneous bloating episode or once challenged with a flatulogenic diet, luminal gas was found to be increased and/or abnormally distributed in about one-fourth of the patients. These patients detected outside the normal range by the classifier exhibited a significantly greater number of abnormal features than those within the normal range (3.7 ± 0.4 vs 0.4 ± 0.1; p < 0.001).

CONCLUSIONS & INFERENCES

The analysis of a large cohort of subjects using original techniques provides unique and heretofore unavailable information on the volume and distribution of intestinal gas in normal conditions and in relation to functional gastrointestinal symptoms.

Food components and irritable bowel syndrome

Ingestion of food has long been linked with gut symptoms, and there is increasing interest in using diet in the management of patients with irritable bowel syndrome (IBS). The West has developed an intense interest in specialized, restrictive diets, such as those that target multiple food groups, avoid gluten, or reduce fermentable oligo-, di-, and mono-saccharides and polyols. However, most gastroenterologists are not well educated about diets or their effects on the gut. It is important to understand the various dietary approaches, their putative mechanisms, the evidence that supports their use, and the benefits or harm they might produce. The concepts behind, and delivery of, specialized diets differ from those of pharmacologic agents. High-quality research is needed to determine the efficacy of different dietary approaches and the place of specific strategies.

Abdominothoracic mechanisms of functional abdominal distension and correction by biofeedback

BACKGROUND & AIMS

In patients with functional gut disorders, abdominal distension has been associated with descent of the diaphragm and protrusion of the anterior abdominal wall. We investigated mechanisms of abdominal distension in these patients.

METHODS

We performed a prospective study of 45 patients (42 women, 24-71 years old) with functional intestinal disorders (27 with irritable bowel syndrome with constipation, 15 with functional bloating, and 3 with irritable bowel syndrome with alternating bowel habits) and discrete episodes of visible abdominal distension. Subjects were assessed by abdominothoracic computed tomography (n = 39) and electromyography (EMG) of the abdominothoracic wall (n = 32) during basal conditions (without abdominal distension) and during episodes of severe abdominal distension. Fifteen patients received a median of 2 sessions (range, 1-3 sessions) of EMG-guided, respiratory-targeted biofeedback treatment; 11 received 1 control session before treatment.

RESULTS

Episodes of abdominal distension were associated with diaphragm contraction (19% ± 3% increase in EMG score and 12 ± 2 mm descent; P < .001 vs basal values) and intercostal contraction (14% ± 3% increase in EMG scores and 6 ± 1 mm increase in thoracic antero-posterior diameter; P < .001 vs basal values). They were also associated with increases in lung volume (501 ± 93 mL; P < .001 vs basal value) and anterior abdominal wall protrusion (32 ± 3 mm increase in girth; P < .001 vs basal). Biofeedback treatment, but not control sessions, reduced the activity of the intercostal muscles (by 19% ± 2%) and the diaphragm (by 18% ± 4%), activated the internal oblique muscles (by 52% ± 13%), and reduced girth (by 25 ± 3 mm) (P ≤ .009 vs pretreatment for all).

CONCLUSIONS

In patients with functional gut disorders, abdominal distension is a behavioral response that involves activity of the abdominothoracic wall. This distension can be reduced with EMG-guided, respiratory-targeted biofeedback therapy.

Intestinal gas homeostasis: disposal pathways

BACKGROUND

Patients with functional gut disorders frequently complain of gas-related symptoms, but the role of intestinal gas in this context is not clear, because intestinal gas homeostasis is incompletely understood. Our aim was to compare the proportion of the gas produced by colonic fermentation that is evacuated per anus and that eliminated via alternative pathways.

METHODS

In 20 healthy subjects, gas evacuated per anus was collected for 4 h after a standard flatulogenic test meal. Paired studies were performed without and with high-rate infusion of exogenous gas (24 mL/min) into the jejunum to wash-out of the gut the endogenous gas produced by bacterial fermentation. The exogenous gas infused was labeled (5% SF₆) to calculate the proportion of endogenous gas evacuated.

KEY RESULTS

In the experiments with gaseous wash-out, 1817 ± 139 mL of endogenous gas was produced over the 4-h study period. However, in the experiments without wash-out (basal conditions), 376 ± 43 mL were evacuated, indicating that only 23 ± 3% of the gas produced was finally eliminated per anus, while the rest (77 ± 3%) had been previously eliminated via alternative pathways.

CONCLUSIONS & INFERENCES

Intestinal gas homeostasis is a highly dynamic process by which a large proportion of the gas produced by bacterial fermentation of meal residues is rapidly absorbed into the blood and/or metabolized by gas-consuming microorganisms, and only a relatively modest proportion is eliminated per anus. These data contribute to clarify the complex dynamics of intestinal gas and may help interpret the pathophysiology of gas-related symptoms.

Long-term bowel disorders following radial cystectomy: an underestimated issue?

PURPOSE

Patients after radical cystectomy (RC) frequently complain about bowel disorders (BDs). Reports addressing related long-term complications are sparse. This cross-sectional study assessed changes in bowel habits (BH) after RC.

METHODS

A total of 89 patients with a minimum follow-up ≥1 year after surgery were evaluated with a questionnaire. Patients with BD prior to surgery were excluded. Symptoms such as diarrhea, constipation, bloating/flatulence, incomplete defecation, uncontrolled stool loss, and impact on quality of life (QoL) were assessed.

RESULTS

A total of 46.1 % of patients reported changes in BH; however, only 25.8 % reported experiencing related dissatisfaction. Primary causes of dissatisfaction were diarrhea and uncontrolled stool loss. The most common complaints were bloating/flatulence and the feeling of incomplete defecation, but these symptoms did not necessarily lead to dissatisfaction or impairment in quality of life. No difference was identified between an orthotopic neobladder and ileal conduit, and even patients without bowel surgery were affected. QoL, health status, and energy level were significantly decreased in unsatisfied patients.

CONCLUSIONS

About 25 % of patients complain about BDs after RC. More prospective studies assessing symptoms, comorbidities, and dietary habits are necessary to address this issue and to identify strategies for follow-up recommendations.

Bloating and functional gastro-intestinal disorders: Where are we and where are we going?

Bloating is one of the most common and bothersome symptoms complained by a large proportion of patients. This symptom has been described with various definitions, such as sensation of a distended abdomen or an abdominal tension or even excessive gas in the abdomen, although bloating should probably be defined as the feeling (e.g. a subjective sensation) of increased pressure within the abdomen. It is usually associated with functional gastrointestinal disorders, like irritable bowel syndrome, but when bloating is not part of another functional bowel or gastrointestinal disorder it is included as an independent entity in Rome III criteria named functional bloating. In terms of diagnosis, major difficulties are due to the lack of measurable parameters to assess and grade this symptom. In addition, it is still unclear to what extent the individual patient complaint of subjective bloating correlates with the objective evidence of abdominal distension. In fact, despite its clinical, social and economic relevance, bloating lacks a clear pathophysiology explanation, and an effective management endorsement, turning this common symptom into a true challenge for both patients and clinicians. Different theories on bloating etiology call into questions an increased luminal contents (gas, stools, liquid or fat) and/or an impaired abdominal empting and/or an altered intra-abdominal volume displacement (abdomino-phrenic theory) and/or an increased perception of intestinal stimuli with a subsequent use of empirical treatments (diet modifications, antibiotics and/or probiotics, prokinetic drugs, antispasmodics, gas reducing agents and tricyclic antidepressants). In this review, our aim was to review the latest knowledge on bloating physiopathology and therapeutic options trying to shed lights on those processes where a clinician could intervene to modify disease course.

Mechanisms of postprandial abdominal bloating and distension in functional dyspepsia

OBJECTIVE

Patients with irritable bowel syndrome and abdominal bloating exhibit abnormal responses of the abdominal wall to colonic gas loads. We hypothesised that in patients with postprandial bloating, ingestion of a meal triggers comparable abdominal wall dyssynergia. Our aim was to characterise abdominal accommodation to a meal in patients with postprandial bloating.

DESIGN

A test meal (0.8 kcal/ml nutrients plus 27 g/litre polyethylenglycol 4000) was administered at 50 ml/min as long as tolerated in 10 patients with postprandial bloating (fulfilling Rome III criteria for postprandial distress syndrome) and 12 healthy subjects, while electromyographic (EMG) responses of the anterior wall (upper and lower rectus, external and internal oblique via bipolar surface electrodes) and the diaphragm (via six ring electrodes over an oesophageal tube in the hiatus) were measured. Means +/- SD were calculated.

RESULTS

Healthy subjects tolerated a meal volume of 913±308 ml; normal abdominal wall accommodation to the meal consisted of diaphragmatic relaxation (EMG activity decreased by 15±6%) and a compensatory contraction (25±9% increase) of the upper abdominal wall muscles (upper rectus and external oblique), with no changes in the lower anterior muscles (lower rectus and internal oblique). Patients tolerated lower volume loads (604±310 ml; p=0.030 vs healthy subjects) and developed a paradoxical response, that is, diaphragmatic contraction (14±3% EMG increment; p<0.01 vs healthy subjects) and upper anterior wall relaxation (9±4% inhibition; p<0.01 vs healthy subjects).

CONCLUSIONS

In functional dyspepsia, postprandial abdominal distension is produced by an abnormal viscerosomatic response to meal ingestion that alters normal abdominal accommodation.

Colonic gas transit in patients with bloating: the effect of an electromechanical stimulator of the abdominal wall

BACKGROUND

The aim of our study was to evaluate gas retention, abdominal symptoms and changes in girth circumference in females with bloating using an active or sham abdominal wall mechanical stimulation.

METHODS

In 14 female patients, complaining of bloating (11 with irritable bowel syndrome and 3 with functional bloating according to the Rome III criteria) a gas mixture was continuously infused into the colon for 1 h (accommodation period). Abdominal perception and girth were measured. At the beginning of the 30-min period of free rectal gas evacuation (clearance period), an electromechanical device was positioned on the abdominal wall of all patients. The patients were randomly assigned to an active or a sham stimulation protocol group. Gas retention, perception and abdominal distension were measured at the end of the clearance period.

RESULTS

All patients tolerated the volume (1,440 ml) of gas infused into the colon. Abdominal perception and girth measurements was similar in both groups during the accommodation period. At the end of the clearance, the perception score and the girth changes in the active and sham stimulation groups were similar (2.8 ± 2.0 vs. 1.4 ± 1.2, p = 0.2 and 4.9 ± 4.5 vs. 2.8 ± 2.3 mm, p = 0.3 active vs. sham, respectively). Furthermore, the mechanical stimulation of the abdominal wall did not significantly reduce gas retention (495 ± 101 ml vs. 566 ± 55, active vs. sham, p = 0.1).

CONCLUSIONS

An external mechanical massage of the abdominal wall did not improve intestinal gas transit, abdominal perception and abdominal distension in our female patients complaining of functional bloating.

Dietary lipids and functional gastrointestinal disorders

There is convincing evidence that patients with functional gastrointestinal disorders (FGIDs) exhibit dysfunctions of the gut involving hypersensitivity and abnormal reflexes, so that physiological, normally unperceived, stimuli induce symptoms. The type of symptoms depends on the specific sensory-reflex pathways and region(s) affected. Fat modulates the responses of the gut to various stimuli, and some of these modulatory mechanisms are abnormal in patients with FGIDs. Indeed, laboratory-based studies have shown that the symptoms experienced by these patients can be induced, or exacerbated, by administration of lipids in amounts that are well tolerated by healthy controls, and, thus, demonstrate a hypersensitivity to lipid. Very few studies have evaluated dietary patterns and eating behavior in these patients, with often-conflicting outcomes, and no studies have been performed to evaluate the role of targeted dietary interventions for the relief of symptoms. Given the evidence from laboratory studies, as well as patient experience, such studies, in large cohorts of patients, are needed with the view to develop personalized, cost-effective treatment approaches.

Abdominal accommodation induced by meal ingestion: differential responses to gastric and colonic volume loads

BACKGROUND

Using an experimental model of colonic gas infusion, we previously showed that the abdominal walls adapt to its content by an active phenomenon of abdominal accommodation. We now hypothesized that abdominal accommodation is a physiological phenomenon, and aimed to confirm that it can be induced by ingestion of a meal; a secondary aim was to determine whether the response to gut filling is region-specific.

METHODS

In healthy subjects (n = 24) a nutrient test meal was administered until tolerated at a rate of 50 mL min(-1). Electromyographic (EMG) activity of the anterior wall (upper and lower rectus, external and internal oblique) was measured via four pairs of surface electrodes, and EMG activity of the diaphragm via intraluminal electrodes on an esophageal tube. To address the secondary aim, the response to gastric filling was compared with that induced by colonic filling (1440 mL 30 min(-1) anal gas infusion; n = 8).

KEY RESULTS

Participants tolerated 927 ± 66 mL of meal (450-1500 mL). Meal ingestion induced progressive diaphragmatic relaxation (EMG reduction by 16 ± 2%; P < 0.01) and selective contraction of the upper abdominal wall (24 ± 2% increase in activity of the upper rectus and external oblique; P < 0.01 for both), with no significant changes in the lower rectus (4 ± 2%) or internal oblique (5 ± 3%). Colonic gas infusion induced a similar response, but with an overall contraction of the anterior wall.

CONCLUSIONS & INFERENCES

Meal ingestion induces a metered and region-specific response of the abdominal walls to accommodate the volume load. Abnormal abdominal accommodation could be involved in postprandial bloating.

Intestinal gas: has diet anything to do in the absence of a demonstrable malabsorption state?

PURPOSE OF REVIEW

To summarize the relevant publications during the last 12 months supporting that diet can influence gas-related symptoms in the absence of a malabsorption state.

RECENT FINDINGS

Gas symptoms during carbohydrate fermentation: a diet incorporating beans is well tolerated by a majority of individuals involved in a program of heart disease biomarkers. By contrast, in patients with irritable bowel syndrome, a diet avoiding fermentable carbohydrates improved gas-related abdominal symptoms. The rate of fermentation determines the production of abdominal symptoms, and many slowly fermentable fibers have a rapid fermentation profile that can generate abdominal symptoms. Modulation of visceral sensitivity: diet can influence gas symptoms by increasing the tolerability of the intestine to gas. Capsaicin decreases visceral hyperalgesia and improved bloating in patients with irritable bowel syndrome. Changes in gas-producing bacteria: different strains of Lactobacillus have antimicrobial properties against gas-forming coliforms. New clinical studies show beneficial effects of prebiotics and probiotics on abdominal bloating.

SUMMARY

Actual data suggest that diet could improve gas-related abdominal symptoms acting on several mechanisms: gas production, visceral hypersensitivity and modulation of gas-producing enteric bacteria.

Accommodation of the abdomen to its content: integrated abdomino-thoracic response

BACKGROUND

  We previously showed that changes in intra-abdominal content induce a volume-dependent muscular response of the anterior abdominal wall and the diaphragm. We aimed to determine the contribution of the thorax to abdominal accommodation and the influence of the intra-abdominal expansion rate.

METHODS

  Gas (1440 mL total load) was infused into the colon of nine healthy subjects, while abdomino-thoracic perimeters (by tape measure), electromyography (EMG) activity of the diaphragm (via six ring electrodes over an esophageal tube in the hiatus), intercostals and anterior abdominal wall (via five pairs of surface electrodes) and the position of the diaphragm by ultrasonography were measured. Infusion rates of 24, 48, and 96 mL min(-1) were tested on separate days.

KEY RESULTS

  Gas infusion induced anterior abdominal wall contraction (18 ± 1% EMG increment; P < 0.001) with relatively modest girth increment (4.9 ± 0.9 mm; P = 0.001), diaphragmatic relaxation (by 15 ± 1%; P < 0.001) with cephalad displacement (by 23 ± 6 mm; P = 0.005), and intercostal contraction (by 19 ± 2%; P < 0.001) with increased thoracic perimeter (by 2.0 ± 0.5 mm; P = 0.009). Responses were similar with the three infusion rates.

CONCLUSIONS & INFERENCES

  Accommodation of intra-abdominal loads involves a volume-related integrated abdomino-thoracic response regardless of the expansion rate.

Pathophysiology, evaluation, and treatment of bloating: hope, hype, or hot air?

Abdominal bloating is commonly reported by men and women of all ages. Bloating occurs in nearly all patients with irritable bowel syndrome, and it also occurs in patients with other functional and organic disorders. Bloating is frequently disturbing to patients and frustrating to clinicians, as effective treatments are limited and are not universally successful. Although the terms bloating and abdominal distention are often used interchangeably, these symptoms likely involve different pathophysiologic processes, both of which are still not completely understood. The goal of this paper is to review the pathophysiology, evaluation, and treatment of bloating and abdominal distention.

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.

Colonic responses to gas loads in subgroups of patients with abdominal bloating

OBJECTIVES

We sought to evaluate colonic gas accommodation, ileocecal competence, and colonic clearance in subgroups patients with abdominal bloating.

METHODS

Thirty-six patients complaining of abdominal bloating (12 constipation-predominant irritable bowel syndrome (IBS-C), 12 diarrhea-predominant irritable bowel syndrome (IBS-D), and 12 functional bloating) and 18 healthy controls were studied. Abdominal perception and girth were measured during: (i) 1 h continuous infusion of gas at 24 ml/min into the rectum (accommodation period) and (ii) 30 min free rectal gas evacuation (clearance period). In eight patients and eight healthy subjects, the gas infused was labeled with radioactive xenon (74 MBq (133)Xe), and gas distribution was determined by scintigraphy.

RESULTS

Colonic gas accommodation produced significantly more abdominal symptoms and distension in patients than in healthy subjects (3.8+/-0.2 vs. 2.4+/-0.3 perception score; P<0.001; 10.9+/-0.6 vs. 8.3+/-0.5 mm girth increment; P=0.009). Scintigraphy showed no differences in colonic gas distribution and no ileal gas reflux, but patients exhibited impaired gas clearance from the proximal colon (63%+/-10% clearance in 30 min vs. 80%+/-2% in health; P=0.042), resulting in more residual gas (506+/-46 vs. 174+/-47 ml; P<0.001), perception (1.9+/-0.2 vs. 1.0+/-0.2 score; P=0.015), and girth increment (4.2+/-0.7 vs. 2.2+/-0.5 mm; P=0.024); IBS-C patients exhibited increased sensation and objective distension, as opposed to sensation only in IBS-D and distension only in functional bloating.

CONCLUSIONS

Patients with abdominal bloating have normal colonic accommodation and ileocecal competence but impaired gas clearance from the proximal colon after retrograde infusion, and the consequences of this dysfunction are related to bowel habit.

Impaired intestinal gas propulsion in manometrically proven dysmotility and in irritable bowel syndrome

BACKGROUND

Intestinal manometry is the current gold standard for diagnosing small bowel dysmotility; however, the functional significance of abnormal manometry is unknown. Our aim was to determine whether, and to what extent, intestinal gas propulsion is impaired in patients with manometrically proven dysmotility compared with healthy controls and patients with IBS.

METHODS

Clearance and tolerance of a jejunal gas load (12 mL min(-1) for 2 h) were measured in 15 patients with severe abdominal symptoms and intestinal dysmotility evidenced by manometry, 15 patients with IBS and 15 healthy subjects. Thereafter, the effect of neostigmine (0.5 mg i.v. bolus) vs placebo (i.v. saline) was tested in six dysmotility patients.

KEY RESULTS

After 2-h gas infusion, patients with dysmotility developed significantly more gas retention (717 +/- 91 mL) than IBS patients (372 +/- 82 mL; P = 0.0037) and healthy subjects (17 +/- 67 mL; P < 0.0001 vs dysmotility; P = 0.0060 vs IBS). Despite the greater retention in dysmotility patients, abdominal perception (2.5 +/- 0.6 score) and distension (7 +/- 2 mm girth increment) were similar to IBS (3.9 +/- 0.6 score and 7 +/- 2 mm, respectively). In dysmotility patients, neostigmine produced immediate clearance of gas, and by 30 min had reduced gas retention (by -552 +/- 182 vs 72 +/- 58 mL after saline; P = 0.008), abdominal symptoms (by -0.8 +/- 0.3 score vs 0.3 +/- 0.2 after saline; P = 0.019) and distension (girth change -5 +/- 1 mm; P = 0.003 vs-2 +/- 2 mm after saline).

CONCLUSION & INFERENCES

Patients with manometric dysmotility have markedly impaired intestinal gas propulsion. In IBS patients, impaired gas propulsion is less pronounced but associated with concomitant sensory dysfunction and poor tolerance of gas retention.

Peripheral factors in the pathophysiology of irritable bowel syndrome

The pathophysiology of IBS is complex and still incompletely known. Both central and peripheral factors are thought to contribute to the symptoms of IBS, including psychosocial factors, abnormal GI motility and secretion, and visceral hypersensitivity. In this review the involvement of peripheral factors in the pathophysiology in IBS is reviewed. Altered GI motility is commonly found in this patient group, even though a specific motor pattern has been hard to find. Colonic transit has been found to be of relevance for the bowel habit of the patient. Abnormal gas handling within the gut is also commonly seen, and seems to be one, but not the only factor responsive for bloating. There is also limited evidence supporting the presence of abnormal GI secretion in IBS, but its relevance for symptoms remains unclear. Visceral hypersensitivity is currently considered to be one of the most important pathophysiological factors in IBS. It can be modulated by several external and internal factors and recent studies support an association between colorectal sensitivity and the symptoms reported by the patients, especially pain.

[Abdominal bloating: an up-to-date]

Bloating is a common symptom, especially in women. In the clinical practice, it remains a therapeutic challenge. Since recently, its pathophysiology is better understood: an impaired transit of gas (particularly in the small bowel) or a visceral hypersensitivity leading to the induction of an abdominal discomfort despite a normal volume of gas are two of the main causes, far more frequent than an excessive production of gas. Moreover, bloating can be related to abnormal viscera-somatic reflexes promoting both an abdomino-phrenic dyssynergia and the relaxation of the muscles of the abdominal wall. From a therapeutic point of view, the efficacy of the gas absorbants remains to be more documented. Besides the treatment of a constipation and the avoidance of nutrients either highly fermentable or rich in fructose, other therapeutic options include prokinetics and drugs acting on visceral sensitivity. Probiotics are another promising option. In some centers, a non pharmacological therapeutic approach, mainly based on hypnosis, is discussed.

Abdominal distention results from caudo-ventral redistribution of contents

BACKGROUND & AIMS

Abdominal bloating is a frequent symptom in various categories of patients; however, its origin is unclear. Our aim was to establish the mechanisms of abdominal bloating.

METHODS

The study evaluated 56 patients whose predominant symptom was abdominal bloating. Of these, 47 (44 female and 3 male; aged 19-74 years) were diagnosed with functional intestinal disorder by Rome II criteria and 9 (7 female and 2 male; aged 18-64 years) were diagnosed with intestinal dysmotility by gastrointestinal manometry. Computed tomographic scans were obtained before (basal level) and during a severe bloating episode. Control scans were also obtained from 12 healthy subjects (11 female and 1 male; aged 19-62 years). Morpho-volumetric differences between basal and severe bloating scans were measured using an original computer analysis program.

RESULTS

During severe bloating, patients with dysmotility exhibited anterior wall protrusion (23 +/- 4 mm; P < .001 vs basal) associated with a marked increase in total abdominal volume (1.4 +/- 0.3 L; P = .002 vs basal) and with cephalic displacement of the diaphragm. By contrast, in patients with functional intestinal disorder, total abdominal volume barely increased (0.3 +/- 0.1 L; P < .001 vs dysmotility); in these patients, abdominal distention (14 +/- 2 mm anterior wall protrusion; P < .001 vs basal) was related to diaphragmatic descent (-12 +/- 3 mm; R = -0.62; P < .001).

CONCLUSIONS

Abdominal distention might be caused by an increase in intra-abdominal volume or abdomino-phrenic displacement and ventro-caudal redistribution of contents.

Abdominal accommodation: a coordinated adaptation of the abdominal wall to its content

BACKGROUND AND AIM

We previously showed that colonic gas infusion increases the girth and modifies the muscular activity of the anterior abdominal wall. We hypothesized that abdominal accommodation to volume loads is an active process instrumented by the coordinated activity of the anterior wall and the diaphragm.

METHODS

To increase intraabdominal volume in healthy subjects, a gas was infused into the colon (1.44 L in 1 h) while measuring girth (by tape measure) and electromyography (EMG) activity of the anterior wall (via four pairs of surface electrodes) and the diaphragm (via six ring electrodes over an esophageal tube in the hiatus). After preliminary feasibility studies (N = 12), postural activity (N = 6) and responses to colonic gas loads, both with the trunk erect (N = 8) and in supine position (N = 8), were studied. A morphometric analysis was performed by computed tomography, image analysis (N = 8).

RESULTS

In the erect position, anterior wall tone was higher and diaphragmatic tone was lower than in the supine position. With the trunk erect, gas infusion induced diaphragmatic relaxation (by 21 +/- 3%; P < 0.05) and anterior wall contraction (16 +/- 4% EMG increment; P < 0.05). By contrast, in the supine position, it induced diaphragmatic contraction (15 +/- 6%, P < 0.05), while the anterior wall, in the absence of postural tone, showed no change (3 +/- 2%, NS). Gas infusion was associated with girth increase (7.3 +/- 1.0 mm with the trunk erect and 8.6 +/- 1.4 mm in the supine position) and diaphragmatic ascent (17.6 +/- 5.2 mm; P < 0.05).

CONCLUSION

The degree of abdominal distension produced by intraabdominal volume increments results from posture-related abdomino-phrenic muscular responses.

Intestinal gas and bloating: effect of prokinetic stimulation

BACKGROUND

It is unknown if abdominal bloating is attributable to excess abdominal gas or improved by a prokinetic agent.

AIMS

To assess abdominal gas content in functional abdominal bloating and to ascertain the effect of a prokinetic agent on intestinal gas symptoms in these patients.

METHODS

In 20 patients, intra-abdominal gas content and symptoms were quantified before and during treatment with pyridostigmine (30 mg/8 hp. o) in this randomized, placebo-controlled, double-blind study. Daily symptoms were quantified for 5 days before and 10 days during treatment, and abdominal gas volume was quantified by CT imaging before and at the fourth day of treatment. A CT scan was also obtained in 10 healthy subjects.

RESULTS

Before treatment, the total volume of intestinal gas was similar in patients (112 +/- 18 mL) and in healthy controls (116 +/- 20 mL). The treatment-induced change in total and regional intestinal gas volume was not significantly different between pyridostigmine (-4 +/- 18 mL; mean +/- SEM) and placebo (0 +/- 15 mL). However, pyridostigmine reduced the severity of bloating from 3.3 +/- 0.3 to 2.6 +/- 0.4 (P < 0.05), whereas placebo did not (3.2 +/- 0.3 vs 3.0 +/- 0.4), although the change did not reach statistical difference across groups.

CONCLUSION

In patients complaining of functional bloating, the volume and distribution of intestinal gas, measured on nonselected days, is comparable to asymptomatic subjects. Prokinetic stimulation improves bloating sensation without detectable changes in gas content.

Irritable bowel syndrome and bloating

Gaseous symptoms in irritable bowel syndrome (IBS) including eructation, flatulence, and bloating occur as a consequence of excess gas production, altered gas transit, abnormal perception of normal amounts of gas within the gastrointestinal tract, or dysfunctional somatic muscle activity in the abdominal wall. Because of the prominence of gaseous complaints in IBS, recent investigations have focussed on new insights into pathogenesis and novel therapies of bloating. The evaluation of the IBS patient with unexplained gas and bloating relies on careful exclusion of organic disease with further characterisation of the underlying condition with directed functional testing. Treatment of gaseous symptomatology in IBS should be targeted to pathophysiologic defects whenever possible. Available therapies include lifestyle alterations, dietary modifications, enzyme preparations, adsorbents and agents which reduce surface tension, treatments that alter gut flora, and drugs that modulate gut transit.

Gas distribution within the human gut: effect of meals

BACKGROUND AND AIMS

Patients frequently complain of gas symptoms precipitated by meals, but the effect of early digestion on intestinal gas content remains unknown. Our aim was to determine the influence of meals on intestinal gas volume and distribution.

METHODS

First, we developed a CT image analysis program, based on independent software modules, to measure gas content within the gut. The system was validated in nine healthy subjects by taking helical abdominal CT scans before and after rectal infusion of known volumes of air (100-400 mL). In 15 healthy subjects, intestinal gas distribution was measured in fast and early postcibal CT scans. The postcibal scan was taken 99 +/- 22 minutes after a 597 +/- 57 kcal meal.

RESULTS

The volume of gas infused per rectum was detected with an accuracy of 100.4 +/- 3.0%. During fasting, intestinal gas volume was 94 +/- 7 mL (excluding two extreme outliers). After the meal, gas content within the gut increased by 64.7% (up to 149 +/- 21 mL, P < 0.01 vs fast) and the increment occurred in the colon (59 +/- 9 mL precibal vs 121 +/- 20 mL postcibal, P < 0.001), while other gut compartments remained unchanged.

CONCLUSION

Ingestion of a meal activated gas metabolism and increased gas content within the gut. The increment occurred early, presumably prior to colonic fermentation of food substrates and was localized in the distal gut, suggesting that gas had a proximal origin and was propelled caudally.

New insights into the pathogenesis and pathophysiology of irritable bowel syndrome

The pathogenesis and pathophysiology of irritable bowel syndrome is complex and still incompletely known. Potential pathogenetic factors include genes, infectious events, psychological symptoms and other loosely defined environmental factors. Both alterations at the central and peripheral level are thought to contribute to the symptoms of irritable bowel syndrome, including psychosocial factors, abnormal gastrointestinal motility and secretion, and visceral hypersensitivity. Today irritable bowel syndrome is viewed upon as a disorder of dysregulation of the so-called brain-gut axis, involving abnormal function in the enteric, autonomic and/or central nervous systems, with peripheral abnormalities probably dominating in some patients and disturbed central processing of signals from the periphery in others. Lines of evidence also suggest that inflammation within the gastrointestinal tract may be of great importance in at least subgroups of irritable bowel syndrome patients. To conclude, a complex picture of the pathogenesis and pathophysiology of irritable bowel syndrome is emerging, with interactions between several different alterations resulting in the divergent symptom pattern in these patients.