Management of Chronic Abdominal Distension and Bloating

Abdominal bloating and distension are 2 of the most commonly reported gastrointestinal symptoms. Abdominal bloating is characterized by symptoms of trapped gas, abdominal pressure, and fullness. Abdominal distension is defined as a measurable increase in abdominal girth. These symptoms frequently co-exist, although they can occur separately. Defined by Rome IV criteria, functional abdominal bloating and distension commonly coincide with other functional gastrointestinal disorders, such as functional dyspepsia, irritable bowel syndrome, and functional constipation. Abdominal bloating and distension can develop for multiple reasons, including food intolerances, a previous infection that perturbed the intestinal microbiota, disordered visceral sensation, delayed intestinal transit, or an abnormal viscero-somatic reflux. Treatment can be challenging to patients and providers—no regimen has been consistently successful. Successful treatment involves identifying the etiology, assessing severity, educating and reassuring patients, and setting expectations. Therapeutic options include dietary changes, probiotics, antibiotics, prokinetic agents, antispasmodics, neuromodulators, and biofeedback. We review the epidemiology and effects of chronic bloating and distension and pathophysiology, discuss appropriate diagnostic strategies, and assess available treatment options. Abdominal bloating and distension are 2 of the most commonly reported gastrointestinal symptoms. Abdominal bloating is characterized by symptoms of trapped gas, abdominal pressure, and fullness. Abdominal distension is defined as a measurable increase in abdominal girth. These symptoms frequently co-exist, although they can occur separately. Defined by Rome IV criteria, functional abdominal bloating and distension commonly coincide with other functional gastrointestinal disorders, such as functional dyspepsia, irritable bowel syndrome, and functional constipation. Abdominal bloating and distension can develop for multiple reasons, including food intolerances, a previous infection that perturbed the intestinal microbiota, disordered visceral sensation, delayed intestinal transit, or an abnormal viscero-somatic reflux. Treatment can be challenging to patients and providers—no regimen has been consistently successful. Successful treatment involves identifying the etiology, assessing severity, educating and reassuring patients, and setting expectations. Therapeutic options include dietary changes, probiotics, antibiotics, prokinetic agents, antispasmodics, neuromodulators, and biofeedback. We review the epidemiology and effects of chronic bloating and distension and pathophysiology, discuss appropriate diagnostic strategies, and assess available treatment options. Nearly all of the population has felt, at one time or another, gassy, bloated, or distended. For many, these are transient sensations that occur after eating, resolve spontaneously, and do not lead to medical consultation. For others, however, abdominal bloating and distension are chronic, bothersome, and negatively affect daily life. The prevalence of bloating and distension is substantial, ranging from 16% to 31% in the general population, and as high as 66%–90% in patients with irritable bowel syndrome (IBS).1Drossman D.A. Li Z. Andruzzi E. et al.U.S. householder survey of functional gastrointestinal disorders. Prevalence, sociodemography, and health impact.Dig Dis Sci. 1993; 38: 1569-1580Crossref PubMed Scopus (1723) Google Scholar, 2Sandler R.S. Stewart W.F. Liberman J.N. et al.Abdominal pain, bloating and diarrhea in the United States: prevalence and impact.Dig Dis Sci. 2000; 45: 1166-1171Crossref PubMed Scopus (0) Google Scholar, 3Schmulson M. Ortiz O. Santiago-Lomeli M. et al.Frequency of functional bowel disorders among healthy volunteers in Mexico City.Dig Dis Sci. 2006; 24: 342-347Crossref Scopus (57) Google Scholar, 4Zuckerman M.J. Nguyen G. Ho H. et al.A survey of irritable bowel syndrome in Vietnam using the Rome criteria.Dig Dis Sci. 2006; 51: 946-951Crossref PubMed Scopus (19) Google Scholar, 5Jiang X. Locke G.R. Choung R.S. et al.Prevalence and risk factors for abdominal bloating and visible distention: a population-based study.Gut. 2008; 57: 756-763Crossref PubMed Scopus (63) Google Scholar, 6Drossman D.A. Morris C.B. Schneck S. et al.International survey of patients with IBS: symptom features and their severity, health status, treatments, and risk taking to achieve clinical benefit.J Clin Gastroenterol. 2009; 43: 541-550Crossref PubMed Scopus (148) Google Scholar Women generally report higher rates of bloating than men, while patients with IBS with constipation (IBS-C) have higher rates than those with IBS with diarrhea.5Jiang X. Locke G.R. Choung R.S. et al.Prevalence and risk factors for abdominal bloating and visible distention: a population-based study.Gut. 2008; 57: 756-763Crossref PubMed Scopus (63) Google Scholar,7Lacy B.E. Mearin F. Chang L. et al.Functional bowel disorders.Gastroenterology. 2016; 150: 1393-1407Abstract Full Text Full Text PDF Google Scholar, 8Chang L. Lee O.Y. Naliboff B. et al.Sensation of bloating and visible abdominal distension in patients with irritable bowel syndrome.Am J Gastroenterol. 2001; 96: 3341-3347Crossref PubMed Google Scholar, 9Talley N.J. Dennis E.H. Schettler-Duncan E.A. et al.Overlapping upper and lower gastrointestinal symptoms in irritable bowel syndrome patients with constipation or diarrhea.Am J Gastroenterol. 2003; 98: 2454-2459Crossref PubMed Scopus (189) Google Scholar, 10Ringel Y. Williams R.E. Kalilani L. Cook S.F. Prevalence, characteristics, and impact of bloating symptoms in patients with irritable bowel syndrome.Clin Gastroenterol Hepatol. 2009; 7: 68-72Abstract Full Text Full Text PDF PubMed Scopus (69) Google Scholar The impact of chronic abdominal bloating and distension on quality of life is substantial.11Spiegel B. Strickland A. Naliboff B.D. et al.Predictors of patient-assessed illness severity in irritable bowel syndrome.Am J Gastroenterol. 2008; 103: 2536-2543Crossref PubMed Scopus (84) Google Scholar Seventy-five percent of patients with bloating (without IBS) characterize their symptoms as moderate to severe in nature, while 50% report that symptoms cause a reduction in daily activities.2Sandler R.S. Stewart W.F. Liberman J.N. et al.Abdominal pain, bloating and diarrhea in the United States: prevalence and impact.Dig Dis Sci. 2000; 45: 1166-1171Crossref PubMed Scopus (0) Google Scholar The economic impact of chronic bloating and distension has not been well studied. Abdominal bloating is the subjective sensation of gassiness, trapped gas, or a feeling of pressure or being distended without obvious visible distension. Patients also describe a sense of fullness or pressure, which can occur anywhere in the abdomen (epigastric, mid, lower, or throughout). Abdominal distension is the objective physical manifestation of an increase in abdominal girth. Patients commonly describe how they look “like a balloon” or “like I’m pregnant.” Abdominal impedance plethysmography has shown that abdominal girth increases during the course of the day in healthy volunteers, and then returns to baseline levels overnight.12Lewis M.J. Reilly B. Houghton L.A. Whorwhell P.J. Ambulatory abdominal inductance plethysmography: towards objective assessment of abdominal distention in irritable bowel syndrome.Gut. 2001; 48: 216-220Crossref PubMed Scopus (0) Google Scholar Abdominal bloating and distension can occur independently, although they frequently co-exist. One study found that only 50%–60% of patients with bloating report abdominal distension, thus highlighting the distinct nature of these disorders.13Serra J. Azpiroz F. Malegalada J.R. Impaired transit and tolerance of intestinal gas in the irritable bowel syndrome.Gut. 2001; 48: 14-19Crossref PubMed Scopus (274) Google Scholar Patients with chronic functional bloating and distension may be diagnosed using the Rome criteria (see Table 1).7Lacy B.E. Mearin F. Chang L. et al.Functional bowel disorders.Gastroenterology. 2016; 150: 1393-1407Abstract Full Text Full Text PDF Google Scholar Of note, neither symptom is required to be present for a patient to meet Rome criteria for IBS or functional constipation although bloating and distension are frequently present in both disorders and are noted as supporting criteria.Table 1Functional Abdominal Bloating and Distension7Lacy B.E. Mearin F. Chang L. et al.Functional bowel disorders.Gastroenterology. 2016; 150: 1393-1407Abstract Full Text Full Text PDF Google ScholarDiagnostic criteria for functional abdominal bloating and/or distension include:-Recurrent bloating and/or distention occurring at least 1 d/wk on average;-Bloating and distension should be the predominant gastrointestinal symptom;-Patients should not meet criteria for irritable bowel syndrome, functional constipation, functional diarrhea, or postprandial distress syndrome;-Symptom onset should have occurred at least 6 months prior to diagnosis;-Symptoms should be active within the preceding 3 months. Open table in a new tab The etiology for chronic abdominal bloating and distension is complex, often multifactorial in nature, and incompletely understood. The differential diagnosis includes both organic and functional disorders (see Table 2). Most patients believe that their symptoms are due to an increased amount of “gas” within the gastrointestinal (GI) tract, although this accounts for symptoms in only a minority of patients. Normal gas production, absorption, and excretion are illustrated in Figure 1. Computed tomography (CT) imaging has shown that luminal gas increases in only 25% of patients with functional gastrointestinal disorders (FGIDs) during a spontaneous episode of abdominal distension or following consumption of a “high-flatulence” diet.14Benduzú R.A. Barba E. Burri E. et al.Intestinal gas content and distribution in health and in patients with functional gut symptoms.Neurogastroenterol Motil. 2015; 27: 1249-1257Crossref PubMed Scopus (16) Google Scholar The following sections highlight major pathophysiologic causes of bloating and distension (see Figure 2).Table 2Common Causes of Chronic Bloating and DistensionOrganic/pathologic etiologies-Small intestinal bacterial overgrowth-Lactose, fructose, and other carbohydrate intolerances-Celiac disease-Pancreatic insufficiency-Prior gastroesophageal surgery (eg, fundoplication, bariatric surgery)-Gastric outlet obstruction-Gastroparesis-Ascites-Gastrointestinal or gynecologic malignancy-Hypothyroidism-Adiposity-Small intestine diverticulosis-Chronic intestinal pseudo-obstructionDisorders of gut-brain interaction-Irritable bowel syndrome-Chronic idiopathic constipation-Pelvic floor dysfunction-Functional dyspepsia-Functional bloating Open table in a new tab Figure 2Pathophysiology of gas and bloating.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Small intestinal bacterial overgrowth (SIBO) and carbohydrate (eg, lactose and fructose) intolerance are common causes of chronic bloating and distension. Excess small intestine bacteria can cause symptoms due to carbohydrate fermentation with subsequent gas production and stretch and distension of the small intestine. Altered sensation and an abnormal viscerosomatic reflex may also play a role although these mechanisms have not been well studied in patients with SIBO. Carbohydrate intolerance may cause symptoms of bloating and distension due to an increased osmotic load, excess fluid retention, and excess fermentation in the colon. The lack of consensus regarding an ideal test to diagnose SIBO makes it difficult to ascertain its true prevalence. In addition, no prospective trial has evaluated patients diagnosed solely with chronic bloating and distension to determine the prevalence of SIBO or food intolerances, and thus most data come from the best-studied FGID, IBS. A meta-analysis reported the prevalence of SIBO to be 0%–20% in healthy control subjects vs 4%–78% in patients with IBS.15Grace E. Shaw C. Whelan K. et al.Review article: small intestinal bacterial overgrowth – prevalence, clinical features, current and developing diagnostic tests, and treatment.Aliment Pharmacol Ther. 2013; 38: 674-688Crossref PubMed Scopus (0) Google Scholar The prevalence of food intolerance, which has similar symptoms, in the general population approaches 20%.16Lomer M.C.E. Review article: the aetiology, diagnosis, mechanisms, and clinical evidence of food intolerance.Aliment Pharmacol Ther. 2015; 1: 262-275Crossref Scopus (49) Google Scholar The true prevalence of carbohydrate intolerance is unclear as carbohydrate intolerance does not necessarily correspond with carbohydrate malabsorption by breath test. One prospective study of symptomatic patients with various FGIDs (n = 1372) identified a prevalence of lactose intolerance and malabsorption of 51% and 32%, respectively, and a prevalence of fructose intolerance and malabsorption of 60% and 45%, respectively.17Wilder-Smith C.H. Materna A. Wermelinger C. et al.Fructose and lactose intolerance and malabsorption testing: the relationship with symptoms in functional gastrointestinal disorders.Aliment Pharmacol Ther. 2013; 37: 1074-1083Crossref PubMed Scopus (90) Google Scholar Lactase deficiency by itself may not cause malabsorption, as not all individuals who are lactase-deficient become symptomatic after ingesting lactose. This indicates that other factors (eg, genetic predisposition, visceral hypersensitivity) may be required for symptom generation in some patients. No studies have focused solely on the implications of the gut microbiome in the pathogenesis of symptoms of abdominal bloating or distension. In contrast, numerous studies have described the role of the gut microbiota in disorders of gastrointestinal motility, sensation, and intestinal permeability.18Shin A. Preidis G.A. Shulman R. et al.The gut microbiome in adult and pediatric functional gastrointestinal disorders.Clin Gastroenterol Hepatol. 2019; 17: 256-274Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar Quantitative and qualitative differences in the intestinal microbiota have been identified comparing patients with IBS and healthy control subjects.19Kassinen A. Krogius-Kurikka L. Makivuokko H. et al.The fecal microbiota of irritable bowel syndrome patients differs significantly from that of healthy subjects.Gastroenterology. 2007; 133: 24-33Abstract Full Text Full Text PDF PubMed Scopus (689) Google Scholar,20Carroll I.M. Ringel-Kulka T. Chang Y.H. et al.Molecular analysis of the luminal- and mucosal-associated intestinal microbiota in diarrhea-predominant irritable bowel syndrome.Am J Physiol Gastrointest Liver Physiol. 2011; 301: G799-G807Crossref PubMed Scopus (176) Google Scholar One study noted significant reductions in specific taxa from members of the Ruminococcaceae and Eubacteriaceae families among IBS patients without bloating compared with IBS patients with bloating and healthy control subjects.21Ringa-Kulka T. Benson A.K. Carroll I.M. et al.Molecular characterization of the intestinal microbiota in patients with and without abdominal bloating.Am J Physiol Gastrointest Liver Physiol. 2016; 310: G417-G426Crossref PubMed Scopus (12) Google Scholar Bloating is common in patients with gastroparesis (over 50%)22Camilleri M. Chedid V. Ford A.C. et al.Gastroparesis.Nat Rev Dis Primers. 2018; 4: 41Crossref PubMed Scopus (39) Google Scholar and those with small bowel dysmotility (eg, chronic intestinal pseudo-obstruction and scleroderma). A prospective study of more than 2000 patients with functional constipation and IBS-C demonstrated that over 90% reported symptoms of bloating.23Neri L. Iovino P. Laxative Inadequate Relief Survey (LIRS) GroupBloating is associated with worse quality of life, treatment satisfaction, and treatment responsiveness among patients with constipation-predominant irritable bowel syndrome and functional constipation.Neurogastroenterol Motil. 2016; 28: 581-591Crossref PubMed Scopus (12) Google Scholar In IBS-C patients, those with prolonged colonic transit were shown to have greater abdominal distension compared with patients with normal transit.24Agrawal A. Houghton L.A. Reilly B. et al.Bloating and distension in irritable bowel syndrome: the role of gastrointestinal transit.Am J Gastroenterol. 2009; 104: 1998-2004Crossref PubMed Scopus (0) Google Scholar Patients with functional bloating and IBS have impaired gas clearance from the proximal colon but normal colonic accommodation to gas infusion.25Hernando-Harder A.C. Serra J. Azpiroz F. et al.Colonic responses to gas loads in subgroups of patients with abdominal bloating.Am J Gastroenterol. 2010; 105: 876-882Crossref PubMed Scopus (0) Google Scholar Patients with anorectal motor dysfunction may experience bloating and distension owing to an impaired ability to effectively evacuate both flatus and stool. Prolonged balloon expulsion correlates with symptoms of distension among patients with constipation.26Shim L. Prott G. Hansen R.D. et al.Prolonged balloon expulsion is predictive of abdominal distension in bloating.Am J Gastroenterol. 2010; 105: 883-887Crossref PubMed Scopus (25) Google Scholar Pelvic outlet obstruction has been shown to delay colonic transit.27Chiarioni G. Salandini L. Whitehead W.E. Biofeedback benefits only patients with outlet dysfunction, not patients with isolated slow transit constipation.Gastroenterology. 2005; 129: 86-97Abstract Full Text Full Text PDF PubMed Scopus (244) Google Scholar A paradoxical abdominophrenic response, called abdominophrenic dyssynergia, develops in some patients with chronic bloating and distension. During this process the diaphragm contracts (descends) and the anterior abdominal wall muscles relax.28Villoria A. Azpiroz F. Burri E. et al.Abdomino-phrenic dyssynergia in patients with abdominal bloating and distension.Am J Gastroenterol. 2011; 106: 815-819Crossref PubMed Scopus (0) Google Scholar This response is in contrast to the normal physiologic response to increased intraluminal gas, whereby the diaphragm relaxes and the anterior abdominal muscles contract in order to increase the craniocaudal capacity of the abdominal cavity without abdominal protrusion (see Figure 3). An elegant CT scan study demonstrated that patients with functional bloating have significant abdominal wall protrusion and diaphragmatic descent with relatively small increases in intraluminal gas. In comparison, patients with bloating and intestinal dysmotility were found to have marked increases in intraluminal gas content with resulting diaphragmatic ascent.29Accarino A. Perez F. Azpiroz F. et al.Abdominal distension results from caudo-ventral redistribution of contents.Gastroenterology. 2009; 136: 1544-1551Abstract Full Text Full Text PDF PubMed Scopus (77) Google Scholar Abdominophrenic dyssynergia has also been identified in patients with functional dyspepsia (FD) and symptoms of postprandial bloating.30Burri E. Barba E. Huaman J.W. et al.Mechanisms of postprandial abdominal bloating and distension in functional dyspepsia.Gut. 2014; 63: 395-400Crossref PubMed Scopus (37) Google ScholarFigure 4Treatment algorithm for bloating and distension. The asterisk (∗) refers to anemia, gastrointestinal bleeding, weight loss >10% of body weight, and family history of GI malignancy. DRE, digital rectal examination; HBT, hydrogen breath test; HRAM, high-resolution anorectal manometry.View Large Image Figure ViewerDownload Hi-res image Download (PPT) IBS patients with symptoms of bloating alone have heightened visceral hypersensitivity compared with those with symptoms of bloating and distension.31Agrawal A. Houghton L.A. Lea R. et al.Bloating and distension in irritable bowel syndrome: the role of visceral sensation.Gastroenterology. 2008; 134: 1882-1889Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar,32Zhu Y. Zheng X. Cong Y. et al.Bloating and distension in irritable bowel syndrome: the role of gas production and visceral sensation after lactose ingestion in a population with lactase deficiency.Am J Gastroenterol. 2013; 108: 1516-1525Crossref PubMed Scopus (0) Google Scholar Postprandial sensitivity to gastric balloon distension was found strongly correlated with postprandial symptoms, such as bloating, in FD patients.33Farré R. Vanheel H. Vanuytsel T. et al.In functional dyspepsia, hypersensitivity to postprandial distension correlates with meal-related symptom severity.Gastroenterology. 2013; 145: 566-573Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar Conscious perception of intraluminal content and abdominal distension may contribute to symptomatic bloating and this can be amplified by complex brain-gut neural pathways, further influenced by factors such as anxiety, depression, somatization, and hypervigilance.34Malagelada J.R. Accarino A. Azpiroz F. et al.Bloating and abdominal distension: old misconceptions and current knowledge.Am J Gastroenterol. 2017; 112: 1221-1231Crossref PubMed Scopus (21) Google Scholar A detailed clinical history and physical examination is critical to understand the underlying cause of bloating and distention. Details regarding the onset and timing of bloating and distention, the relationship to food or bowel movements, a surgical history (ie, Nissen fundoplication),35Richter J.E. Gastroesophageal reflux disease treatment: side effects and complications of fundoplication.Clin Gastroenterol Hepatol. 2013; 11: 465-471Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar and a careful review of medications (ie, narcotics), supplements, and dietary habits should be obtained.36Cotter T.G. Gurney M. Loftus C.G. Gas and bloating-controlling emissions: a case-based review for the primary care provider.Mayo Clin Proc. 2016; 91: 1105-1113Abstract Full Text Full Text PDF PubMed Google Scholar,37Kamboj A.K. Oxentenko A.S. Workup and management of bloating.Clin Gastroenterol Hepatol. 2018; 16: 1030-1033Abstract Full Text Full Text PDF PubMed Google Scholar A physical examination should include a rectal examination to identify an evacuation disorder in patients with constipation.38Mertz H. Naliboff B. Mayer E.A. Symptoms and physiology in severe chronic constipation.Am J Gastroenterol. 1999; 94: 131-138Crossref PubMed Scopus (89) Google Scholar Information obtained will guide specific diagnostic testing (see Supplementary Table 1). Breath tests (BTs) are a safe, noninvasive test to measure carbohydrate maldigestion based on the carbohydrate of interest. Test substances include glucose, lactulose, fructose, sorbitol, sucrose, and inulin.39Rezaie A. Buresi M. Lembo A. et al.Hydrogen and methane-based breath testing in gastrointestinal disorders: the North American Consensus.Am J Gastroenterol. 2017; 112: 775-784Crossref PubMed Scopus (200) Google Scholar Gas produced during colonic fermentation from nonabsorbed carbohydrates diffuses into the systemic circulation and is excreted in the breath, where it can be quantified.40Gasbarrini A. Corazza G.R. Gasbarrini G. et al.Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference.Aliment Pharmacol Ther. 2009; 29: 1-49PubMed Google Scholar Hydrogen and methane are the gases that are exclusively produced in the GI tract from microbial fermentation. The absorption of lactose, a disaccharide composed of glucose and galactose, is dependent on the activity of the brush border enzyme lactase-phlorizin hydrolase.41Enattah N.S. Sahi T. Savilahti E. Terwilliger J.D. Peltonen L. Järvelä I. Identification of a variant associated with adult-type hypolactasia.Nat Genet. 2002; 30: 233-237Crossref PubMed Scopus (746) Google Scholar Lactose maldigestion produces symptoms of bloating, abdominal cramping, flatulence, and diarrhea. Twenty-five grams of lactose is a standard test dose. An increase of ≥20 ppm of hydrogen or >10 ppm of methane above baseline with associated GI symptoms is a positive test. Lactose BT has good sensitivity (mean value of 77.5%) and excellent specificity (mean value of 97.6%).40Gasbarrini A. Corazza G.R. Gasbarrini G. et al.Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference.Aliment Pharmacol Ther. 2009; 29: 1-49PubMed Google Scholar,42Newcomer A.D. McGill D.B. Thomas P.J. Hofmann A.F. Prospective comparison of indirect methods for detecting lactase deficiency.N Engl J Med. 1975; 293: 1232-1236Crossref PubMed Google Scholar,43Hiele M. Ghoos Y. Rutgeerts P. Vantrappen G. Carchon H. Eggermont E. 13CO2 breath test using naturally 13C-enriched lactose for detection of lactase deficiency in patients with gastrointestinal symptoms.J Lab Clin Med. 1988; 112: 193-200PubMed Google Scholar Fructose is a naturally occurring sugar in fruits, different foods, and sweeteners. The absorptive capacity for fructose in the small intestine is minimal; unabsorbed fructose leads to symptoms of bloating and diarrhea. Controversies exist regarding the amount of fructose to use during BT,44Kyaw M.H. Mayberry J.F. Fructose malabsorption: true condition or a variance from normality.J Clin Gastroenterol. 2011; 45: 16-21Crossref PubMed Scopus (37) Google Scholar although the most widely accepted dose is 25 g. A positive test is an increase ≥20 ppm of hydrogen or >10 ppm of methane above baseline with associated GI symptoms. SIBO can cause symptoms of bloating, abdominal pain, gas, and diarrhea; vitamin deficiencies are less common.45Riordan S.M. McIver C.J. Walker B.M. et al.The lactulose breath hydrogen test and small intestinal bacterial overgrowth.Am J Gastroenterol. 1996; 91: 1795-1803PubMed Google Scholar The gold standard for the diagnosis of SIBO is aspiration and culture of jejunal fluid, but this is rarely performed, as it is costly, cumbersome, and invasive.46Saad R.J. Chey W.D. Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy.Clin Gastroenterol Hepatol. 2014; 12: 1964-1972Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar BT is widely available, inexpensive, and noninvasive, although there are limitations regarding standardization, test performance and interpretation.40Gasbarrini A. Corazza G.R. Gasbarrini G. et al.Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference.Aliment Pharmacol Ther. 2009; 29: 1-49PubMed Google Scholar,46Saad R.J. Chey W.D. Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy.Clin Gastroenterol Hepatol. 2014; 12: 1964-1972Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar Glucose and lactulose are the most accepted substrates.40Gasbarrini A. Corazza G.R. Gasbarrini G. et al.Methodology and indications of H2-breath testing in gastrointestinal diseases: the Rome Consensus Conference.Aliment Pharmacol Ther. 2009; 29: 1-49PubMed Google Scholar,46Saad R.J. Chey W.D. Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy.Clin Gastroenterol Hepatol. 2014; 12: 1964-1972Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar A lactulose breath test is considered positive with a baseline level >20 ppm of hydrogen or >10 ppm of methane, an early peak within 90 minutes, or a sustained increased by >10 ppm more than baseline level.39Rezaie A. Buresi M. Lembo A. et al.Hydrogen and methane-based breath testing in gastrointestinal disorders: the North American Consensus.Am J Gastroenterol. 2017; 112: 775-784Crossref PubMed Scopus (200) Google Scholar A glucose BT is considered positive with an increase of 12 ppm of hydrogen or more over baseline or a baseline >20 ppm of hydrogen or >10 ppm of methane. Malabsorption of wheat and gluten may cause symptoms of bloating, distension and accelerated GI transit in untreated celiac disease.47Pinto-Sanchez M.I. Bercik P. Verdu E.F. Motility alterations in celiac disease and non-celiac gluten sensitivity.Dig Dis. 2015; 33: 200-207Crossref PubMed Scopus (11) Google Scholar Serologic testing using tissue transglutaminase and IgA is recommended for patients with a high pretest probability for celiac disease.48Rubio-Tapia A. Hill I.D. Kelly C.P. Calderwood A.H. Murray J.A. ACG clinical guidelines: diagnosis and management of celiac disease.Am J Gastroenterol. 2013; 108: 656-676Crossref PubMed Scopus (877) Google Scholar Upper endoscopy with small bowel biopsies should be performed to confirm celiac disease in those who test positive. Upper endoscopy is necessary in patients when alarm symptoms are identified (recurrent nausea and vomiting, unexplained anemia, hematemesis, weight loss >10% of body weight, a family history of gastroesophageal malignancy) or when gastric outlet obstruction, gastroparesis or FD is suspected. Upper endoscopy also provides an opportunity to biopsy the small intestine and stomach to exclude organic disorders as causes of bloating (see Table 2). An abdominal radiograph can establish stool burden in a patient with coexisting constipation. In patients with prior abdominal surgery, Crohn’s disease, or known or suspected small bowel dysmotility, a CT scan of the abdomen, CT or magnetic resonance imaging enterography, or a careful fluoroscopic examination may be warranted. Bloating is prevalent in patients with gastroparesis.49Hasler W.L. Wilson L.A. Parkman H.P. et al.Bloating in gastroparesis: severity, impact, and associated factors.Am J Gastroenterol. 2011; 106: