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, © 9NONG/DOLLAR PHOTO CLUB and Visiting Gastroenterologist, Sydney and Liverpool Hospitals, Sydney, NSW. MedicineToday ❙ APRIL 2015, VOLUME 16, NUMBER 4 35 Downloaded for personal use only. No other uses permitted without permission. © MedicineToday 2015. ABDOMINAL bloating continued 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. Oligo sac- 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 bacteria. 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 fer mentation 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 36 MedicineToday