Abdominal Blating. Is It All in the Gas?

PEER REVIEWED FEATURE 2 CPD POINTS

Clinical Investigations from the RACP Abdominal bloating Is it all in the gas?

JAMES PANG MB BS, BSci(Med), FRACP bdominal bloating is a common presenting symptom IAN TURNER MB BS(Hons), FRACP in patients in general practice and describes the subjective sensation of abdominal distension with or Bloating is a common problem that is usually without an actual increase in abdominal girth. Patients Acommonly use the term loosely to describe associated symptoms functional, but investigations to exclude organic disease may be needed depending on patient age such as belching, borborygmi and excessive flatus, as well as and symptoms and signs. Treatment should be subjective abdominal distension. A recent survey from the USA found that almost 20% of the general population experiences individualised and usually begins with dietary 1 changes, followed by a short-term trial of abdominal bloating. Surveys have found that almost half to three quarters of patients with bloating reported a concomitant increase medications if needed. in abdominal girth.2 Bloating may be a symptom of an organic disease such as coeliac or inflammatory bowel disease or ovarian cancer. How- ever, it is also a frequent complaint in patients with functional gastrointestinal (GI) disorders, occurring either in isolation – KEY POINTS termed functional bloating – or as part of another disorder such as irritable bowel syndrome (IBS), functional dyspepsia or • Bloating is a common presenting symptom of functional functional constipation. Indeed, bloating can affect up to 96% gastrointestinal (GI) disorders, occurring either in of individuals with IBS.2 Functional bloating is defined by the isolation (functional bloating) or as part of a disorder such Rome III diagnostic criteria for functional GI disorders as a as irritable bowel syndrome (IBS); more rarely, it is a recurrent feeling of bloating or visible distension at least three manifestation of an organic disease. days per month in the past three months, with insufficient criteria • The underlying pathophysiological mechanisms for bloating have been difficult to define but likely involve retained for a diagnosis of functional dyspepsia, IBS or other functional 3 intraluminal gas, altered GI motility and visceral GI disorder. hypersensitivity. Patients often attribute bloating and associated symptoms • Functional bloating and bloating as a manifestation of IBS solely to the production of intestinal gas. Although much research can usually be diagnosed clinically, but judicious use of has focused on the role of intestinal gas in bloating, other factors investigations to exclude organic disease should be such as distorted perception, changes in other intra-abdominal considered. • Treatment of functional bloating is challenging; a trial of lifestyle and dietary changes is appropriate, including a diet MedicineToday 2015; 16(4): 35-40 low in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), with dietitian overview. Dr Pang is a Consultant Gastroenterologist; and Dr Turner is a Consultant • A trial of simple measures such as proton-pump inhibitors, Gastroenterologist and Head of the Department of Gastroenterology, the herbal mixture Iberogast, peppermint oil capsules or Campbelltown Hospital, Sydney, NSW. probiotics might be beneficial in some patients. SERIES EDITOR: Christopher S. Pokorny, MB BS, FRACP, FRCP, FACG, is Copyright _Layout 1 17/01/12 1:43 PM Page 4 Conjoint Associate Professor of Medicine at the University of New South Wales,

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contents and visceral reflexes also play an through the fermentation of complex car- also greater objective abdominal distension important role. bohydrates and nonabsorbable fibre. than healthy subjects.7 These studies sug- Carbon dioxide is mainly produced in gest that although e xcessive intraluminal Mechanisms of bloating the upper GIT by the interaction between gas appears a p lausible cause of abdominal The aetiology of bloating and abdominal gastric acid and bicarbonate in pancreatic bloating and distension, there must be distension is multifactorial. Factors that juice. This chemical reaction is the result other contributing factors. are suggested to contribute to bloating are of fat, carbohydrate and protein metabo- summarised in Figure 1.4 It is thought to lism and occurs rapidly when food reaches Altered gastrointestinal transit involve a combination of: the duodenum. Carbon dioxide is highly Slowed transit of food in the upper GIT • retained abdominal gas soluble and is rapidly absorbed in the upper may cause bloating by several mechanisms. • impaired GI motility GIT but may contribute to bloating in some Firstly, in patients with acquired causes of • visceral hypersensitivity patients, especially those with altered GI slowed transit such as diabetes-related • malabsorption. transit (see below). gastroparesis or abdominal surgery (e.g. In patients with IBS, bloating is quite Hydrogen and methane are produced partial gastrectomy, especially with con- often associated with symptoms such as mainly in the colon by fermentation of food comitant vagotomy), the movement of constipation or diarrhoea. Bloating can residue by the gut microflora, whose com- ingested food to the rest of the GIT is also occur in healthy individuals, espe- position is largely determined by dietary delayed, leading to stasis and a physical cially after overindulgence in large meals. and environmental factors but remains increase in the intraluminal content. This self-induced bloating is rarely a cause fairly stable throughout life. Oligosac Secondly, slowed transit may lead to for concern or medical consultation. Gen- charides and resistant starches (e.g. pota- small bowel bacterial overgrowth – an erally, patients easily connect the bloating toes, oats) are not completely digested in imbalance in the quantity and distribution sensation to excess eating and experience the small bowel and are metabolised by of b acteria. The duodenum and proximal spontaneous relief, usually in a few hours. bacteria in the large bowel, producing jejunum normally contain very few large quantities of hydrogen and carbon bacteria; small bowel bacterial over- Gastrointestinal gas dioxide. These gases are then consumed growth prolongs the fermentation of food The GI tract (GIT) is about eight metres by colonic bacteria to produce methane. residue, leading to excessive gas produc- in length, but the total volume of GI gas The balance between gas-producing and tion. Other causes of slowed GI transit is only about 100 to 200 mL.5 Major gas-consuming micro-organisms deter- include hypothyroidism, scleroderma and sources of GI gas are illustrated in Figure 2 mines the net p roduction of gas. use of medications such as opioids and and discussed below. The distribution of the three gases some antidepressants. varies at different points in the GIT and at A large proportion of patients with bloat- Aerophagia any time, depending on GI gas-handling ing complain that their symptoms worsen Swallowed air is a major source of GI gas. mechanisms such as absorption and as the number of days without a bowel Much aerophagia occurs during eating and expulsion as flatus. motion increases. In patients with consti- drinking and can be a source of bloating pation, the incidence of bloating may be up in those who are sensitive to the effects of Gastrointestinal gas and symptoms to 80%.8 IBS can be classified by the patient’s excess gas. Aerophagia may also occur with The net amount of gas in the GIT at any predominant GI symptom – constipation anxiety or repetitive attempts to induce time is the sum of the amounts swallowed (IBS-C) or diarrhoea (IBS-D) dominant. belching, which may actually increase the and produced in the GIT lumen minus the Patients with IBS-C are thought to retain amount of air swallowed. Carbonated amounts absorbed and expelled by belch- more gas than those with IBS-D, because beverages can introduce a large amount of ing and flatus. Despite the common belief of the slower intestinal transit of fluid and gas into the stomach and, although carbon of both patients and clinicians that gas and subsequent expulsion through dioxide is generally well absorbed in the excessive GI gas is the cause of bloating, defaecation and flatus. Patients with IBS-C small bowel, can cause symptoms in sen- experimental studies using a variety of gas have been found 14 times more likely to sitive patients. washout techniques have failed to detect have bloating or distension than control any significant differences in gas volume subjects.9 However, the relationship between Intestinal production of gas between people with abdominal bloating GI transit patterns and bloating is far from The GIT contains a complex ecosystem of and healthy control subjects.6 In a study of clear cut, with bloating seen in both patients numerous micro-organisms, which are patients given a direct infusion of gas into with IBS-C and those with IBS-D, which vital for maintenanceCopyright of its function_Layout 1 and 17/01/12 the 1:43GIT, PM those Page with 4 a history of b loating are associated with slow and rapid GI integrity. The gut bacteria produce gas developed not only greater symptoms but transit, respectively.10

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Aerophagia, Abnormal viscerosomatic carbonated → Air/CO2 reflexes, abdominophrenic beverages disco-ordination Sex hormones

Altered gut flora, CNS–ENS + abnormal colonic Gastric acid (H ) + dysregulation, fermentation pancreatic juice in psychological – Bloating duodenum (HCO3 ) factors Abdominal → CO2 Excessive gas, distension Altered focal or general gastro gas accumulation, intestinal abnormal gas motility handling Bacterial fermentation → H2+CO2 of food Visceral Constipation, CH hypersensitivity hard stools 4 Abnormal visceral reflexes

Figure 1. Factors that may contribute to abdominal bloating.4 ABBREVIATIONS: CNS = central nervous system; ENS = enteric nervous system. Figure 2. Major sources of gastrointestinal gas.

Visceral hypersensitivity loss. Anxiety and depression were shown in Investigation of bloating Visceral hypersensitivity relates to the way a recent meta-analysis to be significantly A thorough clinical history and physical the central nervous system (CNS) interprets more common in patients with IBS than in examination are needed to clarify what the changes in total abdominal content and healthy control subjects.14 In fact, some patient means by bloating and to ensure girth. Signals emanating from the abdo- studies have shown that up to 60% of that organic disease is excluded before men, such as changed tone of the abdominal patients with IBS have major psychosocial bloating can be considered to be functional. wall muscles and diaphragm, have been problems.15 Consequently, patients with IBS The need for investigations depends on the shown to be important in the perception should be routinely checked for psychiatric patient’s age and associated symptoms. The of bloating.11 More importantly, the way comorbidities and treated accordingly. differential diagnosis of bloating is shown that the CNS perceives these changes in in Box 2, and ‘red flag’ signs and symptoms sensory input from the GIT can also be a Malabsorption of carbohydrates that warrant further investigations are significant contributing factor to patients’ Lactose intolerance is the most common listed in Box 3. perception of their symptoms. subtype of carbohydrate malabsorption Some patients who complain of bloating The GIT–brain interactions are complex. and is frequently found in patients with have associated symptoms such as consti- It is believed that abdominal symptoms can IBS. It is related to low lactase activity. pation, urgency, crampy abdominal pain or influence anxiety and depression, and con- Lactase is an enzyme located in the villous increased stool frequency. These symptoms versely psychological factors can influence membrane of small bowel cells, where it generally increase the likelihood that IBS is GI pain perception and motor functions.12 hydrolyses lactose to glucose and galactose, the underlying cause and decrease the need Psychiatric diagnoses, especially anxiety, which are then absorbed by the cells. for detailed investigation unless other con- depression and somatisation, have been Similarly, malabsorption of other car- cerning symptoms or signs are present. shown to be strong predictors of healthcare bohydrates, such as fructose and sorbitol, seeking.13 Stress, personal experiences and can increase bloating and abdominal dis- Haematology and biochemistry tests psychological problems may produce phys- tension. Malabsorption increases osmotic Iron studies and measurement of red cell

ical complaints that prompt patients to seek load, thereby increasing intraluminal fluid folate and vitamin B12, calcium, albumin medical attention. ForCopyright example, _Layout depression 1 17/01/12 content 1:43 PMand Page altering 4 the variety of GI and vitamin D levels can provide clues

LA GORDA/SHUTTERSTOCK 16 © may lead to a norexia, bloating and weight bacteria flora and GI motility (see Box 1). to a malabsorptive disorder. Anaemia,

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3. GASTROINTESTINAL SIGNS AND 1. ROLE OF FODMAPS IN SYMPTOMS and have superseded antiendomysial anti- OF IRRITABLE BOWEL SYNDROME16 SYMPTOMS THAT WARRANT body testing, which was previously part of FURTHER INVESTIGATION 1. Poorly absorbed FODMAPs are the routine screen for coeliac disease. • Unexplained weight loss presented to the small bowel and colon Abdominal ultrasound and • New symptoms such as abdominal pain (less than six months’ duration) 2. Water is drawn into the lumen computed tomography • Recent changes in bowel habit through osmosis Ultrasound is useful for the assessment of • Nocturnal symptoms (i.e. waking 3. Bacterial fermentation of FODMAPs solid intra-abdominal organs and ascites. from sleep with symptoms) in the colon leads to gas production It is, however, operator dependent, and • Fever and abdominal bloating views may be obscured by excess bowel • Gastrointestinal bleeding ABBREVIATION: FODMAPs = fermentable oligosac gas. It is a relatively inexpensive test and • Age over 50 years at onset charides, disaccharides, monosaccharides and polyols. does not have any associated radiation. CT • Abdominal mass scans are more useful for the diagnosis of 2. DIFFERENTIAL DIAGNOSIS FOR solid organ malignancies. BLOATING Management of bloating Stool microscopy and culture Management of patients with bloating • Functional gastrointestinal disorder Stool microscopy and culture are generally attributed to IBS usually involves control of (e.g. irritable bowel syndrome) ordered for patients with an acute diarrhoeal associated symptoms such as pain, consti- • Peptic ulcer disease illness that has lasted more than a few days. pation and diarrhoea. The evidence base for • Coeliac disease Enteropathic organisms such as salmonella, most pharmacological treatments including • Inflammatory bowel disease (e.g. campylobacter and giardia can cause bloat- prokinetics, which alter GI transit, and Crohn’s disease) ing before the onset of diarrhoea. Post surfactants such as simethicone, is generally • Pancreatic insufficiency infectious IBS can also cause abdominal weak. However, exclusion diets such as a • Lactase deficiency bloating but is usually self-limiting. diet low in FODMAPs (fermentable oligo- • Small bowel bacterial overgrowth saccharides, disaccharides, monosacchar after abdominal surgery such as Faecal calprotectin ides, and polyols) have shown promising partial gastrectomy, Whipple 16 procedure (pancreaticoduodenectomy) Calprotectin is a protein released from neu- results. Gluten sensitivity in the absence of trophils in response to inflammation or coeliac disease as a cause of bloating and • Gastrointestinal or gynaecological malignancy infection of the GIT. Measurement of faecal diarrhoea is controversial. Clinical trials • Ascites (e.g. decompensated liver calprotectin is useful for differentiating have produced different results with respect cirrhosis, cardiac failure, metastatic inflammatory bowel disease from IBS but to the effect of gluten on bloating and other gynaecological and gastrointestinal is not currently Medicare funded. symptoms in patients with IBS.19,20 malignancies with malignant ascites, Given the heterogeneity of bloating- atypical infections such as tuberculosis) Gastroscopy and colonoscopy associated symptoms across the population, Peptic ulcer and gastric cancer can cause treatment should be tailored for each indi- especially if associated with iron deficiency abdominal bloating and should be ruled vidual. Various treatment options may be and weight loss, should prompt consider- out by gastroscopy and/or a urea breath test tried, usually starting with lifestyle ation of occult GI malignancies. for Helicobacter pylori (for peptic ulcer) or and dietary modification, followed by Coeliac disease can manifest in a number gastroscopy (for gastric cancer) if the symp- a short-term trial of pharmacological of ways, including diarrhoea after ingestion toms are suggestive. The gold standard for therapies. of gluten or unintentional weight loss. Tests the diagnosis of coeliac disease is small bowel for IgA antibodies to tissue transglutaminase biopsy while the patient is ingesting a gluten- Lifestyle modification (TTG) and deamidated gliadin peptide have containing diet. Small bowel biopsy can also Bloating can be associated with eating very good sensitivity and specificity for the be undertaken to assess for lactase defi- habits, such as eating rapidly, while ‘on the diagnosis of coeliac disease. Total immuno- ciency, which may give rise to lactose intol- go’ or while watching television. Patients globulin IgA should also be measured, as 2 erance. However, lactose intolerance can should be encouraged to identify the t riggers to 3% of patients with coeliac disease have also occur in patients with normal small for their symptoms themselves, whether selective IgA deficiency.17 In that case, tests bowel lactase activity.18 Colonoscopy with they be the type of food or style of eating. for IgG antibodies to TTG and gliadin biopsies needs to be considered to exclude This allows them ownership of their symp- should be ordered. TheseCopyright tests _Layoutare Medicare 1 17/01/12 inflammatory 1:43 PM Page bowel 4 disease, microscopic toms and treatment by altering eating funded. They are more specific and sensitive colitis and GI malignancies. behaviours and avoiding triggers.

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Dietary modification trial in patients with functional bloating, Conclusion Fibre as it might be a manifestation of reflux or Abdominal bloating is a relatively non The effect of fibre is controversial in bloating peptic ulcer disease. The need for appro- specific term used to describe the sub and its use may worsen symptoms in some priate investigations for these conditions jective sensation of abdominal distension. patients. General advice is often given to should be kept in mind. Despite bloating being common, it is the increase daily fibre intake, especially in those most poorly understood GI symptom and with constipation. However, this can be Antispasmodics may mean different things to different counterintuitive for patients with diarrhoea As a class, antispasmodics have been shown patients. It is important to take a thorough as their predominant symptom, as it will to be of benefit in the treatment of IBS and clinical history and perform a physical increase the amount of water drawn into the associated symptoms.22 They should, how- examination to ascertain and clarify the lumen. A short trial of fibre is not unreason- ever, be used only for short-term relief of patient’s symptoms and to ensure that an able but should not be pursued if it clearly symptoms. Examples include hyoscine and organic disease is excluded before attrib- does not improve the patient’s symptoms. mebeverine. Side effects of these medica- uting bloating to IBS or another functional tions include dry eyes, dry mouth and GI disorder. FODMAPS constipation. Treatment of bloating is unlikely to be FODMAPs are poorly absorbed short- uniform, given the heterogeneity of symp- chain carbohydrates that are thought to Prokinetics toms between patients. Various treatment give rise to abdominal symptoms through Prokinetics may alter the distribution of options may be tried to tailor an effective osmotic effects and gas production via gas in various parts of the GIT without regimen for individual patients. Treatment bacterial fermentation (Box 1). On this detectable changes in total gas content.23 usually begins with dietary modification, premise, a diet that is low in FODMAPs Newer agents such as prucalopride, a selec- followed by a short-term trial of pharma- has been proposed as first-line manage- tive serotonin (5HT4) agonist, have been cological therapies. The effect of anti ment in patients with IBS. In a recently shown to be effective in chronic constipa- spasmodics, prokinetics, and complemen- published randomised controlled crossover tion. Prucalopride is available in Australia tary medicines is variable and inconsistent, study, patients with IBS had fewer symp- only on private script for refractory but short-term use is usually not associated toms of bloating and abdominal pain while constipation.24 with major side effects. MT eating a low-FODMAP diet than while eating a typical Australian diet.21 Antibiotics References Rifaximin is a nonabsorbable antibiotic that A list of references is included in the website version Flatulogenic foods was shown to be more effective than placebo (www.medicinetoday.com.au) and the iPad app Avoidance of ‘flatulogenic’ foods may for improving global IBS symptoms in a version of this article. improve bloating symptoms. These include: recent meta-analysis.25 In addition, it is more COMPETING INTERESTS: None. • foods that contain complex likely to improve symptoms of bloating carbohydrates, such as rice, potatoes, (odds ratio, 1.55; number needed to treat to ONLINE CPD JOURNAL PROGRAM beans and lentils improve symptoms in one patient, 10.1). • carbonated beverages, as they However, it is not currently PBS approved In patients with bloating, what increase the delivery of carbon for this indication and so is relatively signs and symptoms warrant dioxide to the small intestine expensive. further investigations? • artificial sweeteners containing sorbitol and fructose, which are incompletely Complementary medicines absorbed in the small bowel and Patients often use complementary medi- undergo fermentation in the colon. cines, although their efficacy is frequently A consultation with an experienced not proven. Research has shown some dietitian is valuable to identify flatulogenic benefit with the use of enteric-coated foods and ensure a balanced diet is followed. peppermint oil, Iberogast (STW5, a propri-

etary herb mixture) and selected probiotics CLUB PHOTO © RUIGSANTOS/DOLLAR Pharmacological therapy in functional GI disorders, including bloat- Review your knowledge of this topic Proton-pump inhibitors ing.26-28 These products have generally been and earn CPD points by taking part in MedicineToday’s Online CPD Journal Proton-pump inhibitors, although TGA found safe for short-term use and warrant Program. Log in to Copyright _Layout 1 17/01/12 1:43 PM Page 4 approved only for reflux and peptic ulcer a trial for patients with functional www.medicinetoday.com.au/cpd treatment, are warranted for a four-week bloating.

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JAMES PANG MB BS, BSci(Med), FRACP; IAN TURNER MB BS(Hons), FRACP

References

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