Review article: bloating in functional bowel disorders

Abdominal Bloating in the United States: Results of a Survey of 88,795 Americans Examining Prevalence and Healthcare Seeking

BACKGROUND & AIMS

Although abdominal bloating is a common symptom, comparatively little is known about its prevalence in the community. This study aimed to examine the prevalence of bloating and assess related health care seeking using survey data from a nationally representative sample of nearly 89,000 Americans.

METHODS

Participants completed the National Gastrointestinal (GI) Survey II to measure the presence and severity of GI symptoms including bloating. We assessed the prevalence of bloating in the past 7 days, as well as severity and health care seeking for bloating. Multivariable regression was performed to identify associations between the outcomes and covariates.

RESULTS

Of 88,795 survey completers, 12,324 (13.9%) reported bloating in the past 7 days. Women and those with comorbidities (eg, irritable bowel syndrome, chronic constipation, ulcerative colitis) and concomitant GI symptoms (eg, abdominal pain, excess gas) had higher odds for bloating (all P < .001). These factors were also associated with more severe bloating (all P < .001). Among those who reported recent bloating, 58.5% never sought care for bloating-29% of whom were self-managing symptoms or were uncomfortable discussing symptoms with their providers.

CONCLUSIONS

Bloating is common in the community because nearly 1 in 7 Americans have experienced this symptom in the past week. Women and those with certain comorbidities and concomitant GI symptoms are more likely to experience bloating and have more severe symptoms. Nearly one third of sufferers who have not sought care are managing symptoms on their own or are uncomfortable discussing it with their providers, emphasizing that efforts should be made to proactively inquire about bloating.

Targeting Mechano-Transcription Process as Therapeutic Intervention in Gastrointestinal Disorders

Mechano-transcription is a process whereby mechanical stress alters gene expression. The gastrointestinal (GI) tract is composed of a series of hollow organs, often encountered by transient or persistent mechanical stress. Recent studies have revealed that persistent mechanical stress is present in obstructive, functional, and inflammatory disorders and alters gene transcription in these conditions. Mechano-transcription of inflammatory molecules, pain mediators, pro-fibrotic and growth factors has been shown to play a key role in the development of motility dysfunction, visceral hypersensitivity, inflammation, and fibrosis in the gut. In particular, mechanical stress-induced cyclooxygenase-2 (COX-2) and certain pro-inflammatory mediators in gut smooth muscle cells are responsible for motility dysfunction and inflammatory process. Mechano-transcription of pain mediators such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) may lead to visceral hypersensitivity. Emerging evidence suggests that mechanical stress in the gut also leads to up-regulation of certain proliferative and pro-fibrotic mediators such as connective tissue growth factor (CTGF) and osteopontin (OPN), which may contribute to fibrostenotic Crohn's disease. In this review, we will discuss the pathophysiological significance of mechanical stress-induced expression of pro-inflammatory molecules, pain mediators, pro-fibrotic and growth factors in obstructive, inflammatory, and functional bowel disorders. We will also evaluate potential therapeutic targets of mechano-transcription process for the management of these disorders.

Bloating: Avicenna's Perspective and Modern Medicine

Bloating and abdominal distention are common complaints present in quite a number of organic and functional diseases. An important subject in traditional Persian medicine is digestive disorders, particularly bloating and its etiology. This is a literature review study conducted on The Canon in Medicine written by Avicenna and using the keywords: bloating, gas. In this article, causes for bloating, according to Avicenna, include diet causes, inappropriate lifestyle, gastrointestinal, and miscellaneous reasons. These were compared with causes suggested in modern medicine. Avicenna classifies causes based on the place of origin into upper part of the abdomen (stomach) and intestinal part of the abdomen. Also, 38 medicinal plants used as remedies were listed. Modern scientific data support all bloating causes that have been mentioned in the canon. Obviously, some causes such as uterine disorders and posterior nasal discharge need to be studied further.

Colon distention induces persistent visceral hypersensitivity by mechanotranscription of pain mediators in colonic smooth muscle cells

Abdominal pain and distention are major complaints in irritable bowel syndrome. Abdominal distention is mainly attributed to intraluminal retention of gas or solid contents, which may cause mechanical stress to the gut wall. Visceral hypersensitivity (VHS) may account for abdominal pain. We sought to determine whether tonic colon distention causes persistent VHS and if so whether mechanical stress-induced expression (mechanotranscription) of pain mediators in colonic smooth muscle cells (SMCs) plays a role in VHS. Human colonic SMCs were isolated and stretched in vitro to investigate whether mechanical stress upregulates expression of the pain mediator cyclooxygenase-2 (COX-2). Rat colon was distended with a 5-cm-long balloon, and gene expression of COX-2, visceromotor response (VMR), and sensory neuron excitability were determined. Static stretch of colonic SMCs induced marked expression of COX-2 mRNA and protein in a force- and time-dependent manner. Subnoxious tonic distention of the distal colon at ∼30-40 mmHg for 20 or 40 min induced COX-2 expression and PGE2 production in colonic smooth muscle, but not in the mucosa layer. Lumen distention also increased VMR in a force- and time-dependent manner. The increase of VMR persisted for at least 3 days. Patch-clamp experiments showed that the excitability of colon projecting sensory neurons in the dorsal root ganglia was markedly augmented, 24 h after lumen distention. Administration of COX-2 inhibitor NS-398 partially but significantly attenuated distention-induced VHS. In conclusion, tonic lumen distention upregulates expression of COX-2 in colonic SMC, and COX-2 contributes to persistent VHS.

Abdominal bloating: pathophysiology and treatment

Abdominal bloating is a very common and troublesome symptom of all ages, but it has not been fully understood to date. Bloating is usually associated with functional gastrointestinal disorders or organic diseases, but it may also appear alone. The pathophysiology of bloating remains ambiguous, although some evidences support the potential mechanisms, including gut hypersensitivity, impaired gas handling, altered gut microbiota, and abnormal abdominal-phrenic reflexes. Owing to the insufficient understanding of these mechanisms, the available therapeutic options are limited. However, medical treatment with some prokinetics, rifaximin, lubiprostone and linaclotide could be considered in the treatment of bloating. In addition, dietary intervention is important in relieving symptom in patients with bloating.

Review article: the treatment of functional abdominal bloating and distension

BACKGROUND

Abdominal bloating and distension are common symptoms in patients with functional gastrointestinal disorders (FGIDs), however, relatively little is known about their treatment.

AIM

To review the treatment trials for abdominal bloating and distension.

METHODS

A literature review in Medline for English-language publications through February 2010 of randomised, controlled treatment trials in adults. Study quality was assessed according to Jadad's score.

RESULTS

Of the 89 studies reviewed, 18% evaluated patients with functional dyspepsia, 61% with irritable bowel syndrome (IBS), 10% with chronic constipation and 10% with other FGIDs. No studies were conducted in patients diagnosed with functional abdominal bloating. The majority of trials investigated the efficacy of prokinetics or probiotics, although studies are heterogeneous with respect to diagnostic criteria and outcome measures. In general, bloating and/or distension were evaluated as secondary endpoints or as individual symptoms as part of a composite score rather than as primary endpoints. A greater proportion of IBS patients with constipation reported improvement in bloating with tegaserod vs. placebo (51% vs. 40%, P<0.0001) and lubiprostone (P<0.001). A greater proportion of nonconstipating IBS patients reported adequate relief of bloating with rifaximin vs. placebo (40% vs. 30%, P<0.001). Bloating was significantly reduced with the probiotics, Bifidobacterium infantis 35624 (1×10(8) dose vs. placebo: -0.71 vs. -0.44, P<0.05) and B. animalis (live vs. heat-killed: -0.56±1.01 vs. -0.31±0.87, P=0.03).

CONCLUSIONS

Prokinetics, lubiprostone, antibiotics and probiotics demonstrate efficacy for the treatment of bloating and/or distension in certain FGIDs, but other agents have either not been studied adequately or have shown conflicting results.

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.

Abdominal bloating in employed adults: prevalence, risk factors, and association with other bowel disorders

BACKGROUND Bloating is common, but its significance as a marker of underlying disease has not been defined. AND AIMS: We report on risk factors for bloating, its relationship to physical activity and quality of life (QOL), and its predictive value for functional bowel disorders.

METHODS

This is a cross-sectional population-based study of 1,069 employees of the Veterans Affairs Black Hills Health Care System. The validated Bowel Disease Questionnaire was used to identify subjects with abdominal bloating and other bowel disorders. The association of bloating with QOL was assessed using the SF36 (Short-Form 36) questionnaire. Physical activity was assessed using the modified Baecke questionnaire.

RESULTS

The response rate was 72% (723 of 1,069). Bloating was reported by 21% of all subjects (95% confidence interval [CI] 17.7-23.7), 64% with irritable bowel syndrome (IBS), 35% with non-IBS constipation, 23% with non-IBS diarrhea, and 42% with dyspepsia. Functional bloating (i.e., bloating in the absence of other bowel disorders) was reported by 7% of subjects (95% CI 5.2-9.0). Of those with bloating, 28% had IBS, 25% non-IBS constipation, 8% non-IBS diarrhea, and 30% dyspepsia. The positive and negative predictive values of bloating in the diagnosis of functional bowel disorder were 66% and 87%, respectively. The only risk factors were smoking and high-dose aspirin. Bloating was not associated with physical activity. QOL on all subscales of SF36 was lower in subjects with bloating than those without bloating.

CONCLUSIONS

Bloating is a common symptom in otherwise healthy adults, and is often associated with but not predictive of functional bowel disorders. Smoking and high-dose aspirin are associated with bloating while physical activity is not.

Towards a better understanding of abdominal bloating and distension in functional gastrointestinal disorders

Abdominal bloating is an extremely common symptom affecting up to 96% of patients with functional gastrointestinal disorders and even 30% of the general population. To date bloating has often been viewed as being synonymous with an actual increase in abdominal girth, but recent evidence suggests that this is not necessarily the case. This review examines the relationship between the symptom of bloating and the physical sign of abdominal distension, as well as examining the epidemiology, pathophysiology and treatment options available for this debilitating aspect of the functional gastrointestinal disorders. Pathophysiological mechanisms explored include psychological factors, intestinal gas accumulation, fluid retention, food intolerance and malabsorption of sugars, weakness of abdominal musculature, and altered sensorimotor function. Treatment options are currently rather limited but include dietary changes, pharmacological approaches, probiotics and hypnotherapy.

Definition and classification of irritable bowel syndrome: current consensus and controversies

The symptom-based taxonomy of IBS and other functional bowel disorders is based on defined individual symptoms and the co-occurrence of certain symptoms in individuals. Wording of survey questions to accurately reflect the symptoms can be difficult in English, but accomplishing it for non-English-speakers, especially residents of non-Western societies, is an even greater challenge that needs more attention. The potential for misdiagnosis and inappropriate management, including unnecessary surgery, under-scores the need for wider knowledge of typical IBS symptoms by physicians and the collaboration of primary and specialist physicians in patient care. Even though the evolving symptom classification is as evidence-based as its designers can make it, some arbitrariness is inevitable. Population prevalence rates vary widely, depending on diagnostic criteria and other factors, and further work is needed to determine which individuals detected in surveys consider themselves distressed enough to want medical care and why the remaining people do not feel this need. Clearly, more primary care patients should be studied. Physicians should assess clinical trials critically regarding patient recruitment methods and patient features that could influence whether the results are applicable to their patients. The instability of bowel habit subtypes suggests that relatively few patients should expect relief by taking the same motility-active drug regularly for a long time. Long-term, natural history studies of symptoms and health care use are needed. Discoveries of subtle morphologic pathology and disordered physiology are elucidating IBS pathophysiology further, which some experts believe will lead to a more objective, laboratory-based (organic) diagnosis and more effective therapy. The benefit patients will obtain from supplementing a traditional symptom-based, biopsychosocial approach with such findings remains to be determined. The symptom criteria have had important roles in epidemiological studies and characterizing subjects for clinical trials. Many practitioners, however,do not know the typical symptoms or use the criteria, and investigating how physicians diagnose IBS has received scanty attention. It is unknown how many physicians diagnose IBS by exclusion only after extensively testing patients with typical symptoms and no alarm features, but determining this could have important economic and safety implications. There has been little careful validation of the symptom criteria, especially with primary care patients, and no particular criteria are clearly superior for clinical practice,although the Manning and Rome I criteria have been most evaluated and are less restrictive than the Rome II criteria.

Experimental design for the formulation and optimization of novel cross-linked oilispheres developed for in vitro site-specific release of Mentha piperita oil

A Plackett-Burman design was employed to develop and optimize a novel crosslinked calcium-aluminum-alginate-pectinate oilisphere complex as a potential system for the in vitro site-specific release of Mentha piperita, an essential oil used for the treatment of irritable bowel syndrome. The physicochemical and textural properties (dependent variables) of this complex were found to be highly sensitive to changes in the concentration of the polymers (0%-1.5% wt/vol), crosslinkers (0%-4% wt/vol), and crosslinking reaction times (0.5-6 hours) (independent variables). Particle size analysis indicated both unimodal and bimodal populations with the highest frequency of 2 mm oilispheres. Oil encapsulation ranged from 6 to 35 mg/100 mg oilispheres. Gravimetric changes of the crosslinked matrix indicated significant ion sequestration and loss in an exponential manner, while matrix erosion followed Higuchi's cube root law. Among the various measured responses, the total fracture energy was the most suitable optimization objective (R2 = 0.88, Durbin-Watson Index = 1.21%, Coefficient of Variation (CV) = 33.21%). The Lagrangian technique produced no significant differences (P > .05) between the experimental and predicted total fracture energy values (0.0150 vs 0.0107 J). Artificial Neural Networks, as an alternative predictive tool of the total fracture energy, was highly accurate (final mean square error of optimal network epoch approximately 0.02). Fused-coated optimized oilispheres produced a 4-hour lag phase followed by zero-order kinetics (n > 0.99), whereby analysis of release data indicated that diffusion (Fickian constant k1 = 0.74 vs relaxation constant k2 = 0.02) was the predominant release mechanism.