Managing bloating, flatus and flatulence

* Which foods are most likely to cause bloating and flatus? * What examination and investigations should the GP perform? * Does oral charcoal reduce the smell of flatus? ANDREW JG BELL, BSC, MRCP. Specialist Registrar in Gastroenterology, Gastroenterology Unit, Rayne Institute, St Thomas's Hospital, LondonPAUL J CICLITIRA, MD, PHD, FRCP. Professor of Gastroenterology, Gastroenterology Unit, Rayne Institute, St Thomas's Hospital, LondonFlatus was a hot topic during the Space Race: mission controllers were anxious that the astronaut's hydrogen emissions might accidentally explode with dire consequences. If not, then might the waste gases effectively suffocate them in the sealed module?1This stimulus provided an impetus for research into the volume and composition of bowel gas. The only previous occasion when similar research had been undertaken was following reports of explosive decompression in surfacing submariners in World War II.2* Origins in health Gas in the lower bowel may be partially made up of swallowed air. Nitrogen (N2) is the chief constituent remaining in this fraction due to diffusion of oxygen (O2) into the blood stream.Carbon dioxide (CO2) produced in the small intestine also diffuses out rapidly - hence the observation that post-colonoscopy discomfort is much lower when insufflation with CO2 rather than air has been used.In addition to swallowed air, gas is produced by bacterial fermentation in the colon.3 While we are not equipped to digest certain dietary carbohydrates, bacteria found in the gut are capable of digesting them. Two important examples of these are raffinose and stachyose, which are typically consumed in legumes and beans. The hydrogen (H2) and methane (CH4) found in intestinal gases are exclusively due to metabolism by the colonic flora of carbohydrate in this way.Overall, 99 per cent of colonic gas is made up of a mixture of O2, CO2, N2, H2, CH4. All of these are free of aroma - it is the remaining one per cent that is responsible for the unpleasant odour.Sophisticated gas-liquid chromatography of intestinal gas and less sophisticated assessment of synthetic flatus by panels of judges has shown that the smell is due to volatile elements, including sulphur-based gases like hydrogen sulphide.4These are picked up by the nose in quantities as low as a few parts per million, and probably arise from the action of sulphate-reducing bacteria on sulphate, which is present naturally in cruciferous vegetables like broccoli and cabbage. Sulphates are also an additive in bread and beer, and also present in sulphur-containing amino-acids (methionine and cysteine) in proteins.* Origins in disease Carbohydrate is normally digested to oligosaccharides in the small intestine where specific enzymes such as the dissacharidases lactase and sucrase act to produce glucose, which is readily absorbed by active transport and diffusion.If the small intestine mucosa is damaged then these dissacharidases are reduced or absent and the digosaccharides pass through to the large bowel. The result may be diarrhoea due to the osmotic load and/or increased fermentation with increased gas production.Increased fermentation is therefore seen in coeliac disease and Crohn's disease due to mucosal damage, as well as in specific enzyme deficits such as lactose intolerance and sucrase- isomaltase deficiency. It can take place when physiological maldigestion occurs, as with the slowly-digested digosaccharides fructose and sorbitol, but also in the context of physiological dysfunction leading to maldigestion, as in patients with increased motility.Hydrogen and methane are not only excreted by passing flatus, but also exhaled as the gases diffuse into the blood perfusing the colon and diffuse out again in the lungs. This is exploited in the hydrogen breath test, in which a syringe of expired air is collected at a fixed time after an oral dose of the test carbohydrate. If the H2 level is significantly raised then the carbohydrate is not being digested because of enzyme deficiency, small bowel disease or severe motility disturbance.* Gas dependent disease Concentrations of H2 and CH4 can reach their flash points. Indeed, fatal colonic explosion has followed inadvertent ignition of hydrogen during diathermy polypectomy5 in imperfectly prepared colons.Happily, this seems to be a thing of the past.Many patients recognise intestinal discomfort, which is relieved by passing flatus. There are social reasons for not passing flatus, and more H2 is found to be expired in social situations,6 perhaps because less is passed in flatus. Equally, the reason may be physiological or anatomical.However, the social restraints that we experience may not have been in place in Ancient Rome; Claudius is said to have decreed that Romans might pass gas wherever they were!When no flatus is the cardinal sign of intestinal obstruction this will usually be obvious, certainly on X-ray. However, the so called flexure syndromes in which gas may be seen on X-ray at the splenic or hepatic flexure do not represent an obstruction; these appear to be variants of the irritable bowel syndrome (IBS) and normally respond to anti- constipation measures.7This brings us to the symptom of bloating, which ranks second only to abdominal pain as the most frequent gastrointestinal symptom.We have all met the patient who brings in a picture of the dresses she used to wear but asks you to `look at what I have to wear now'. The patient is often close to tears and dressed in a garment the shape of a tent.Is intestinal gas volume the problem? Do sufferers of bloating have more intestinal gas inside them?No, in a word. Lasser8 used argon to show that patients had an average volume lower than that of controls (176ml vs.199ml).Are they more sensitive to gas volumes? Yes; in the same study the argon infusions in patients who suffered from bloating had to be discontinued, whereas controls did not complain.For the most part, bloating seems to relate to sensory abnormalities, not the objective measure of gas volume and, therefore, appropriately forms part of the definition of IBS.Does it help to make levels of gas subnormal? Using whole-body calorimetry, King9 found that in IBS patients there appeared to be a greater drop in the total H2 produced than in the controls when put on an exclusion diet and, indeed, symptoms were relieved in line with the decline in H2 production.Part of the explanation may be that antibiotics may selectively encourage H2- producers in the flora rather than H2-users. The production of one volume of methane by bacteria uses up two equivalent volumes of hydrogen and, thus, reduces the total.* Has the patient got cancer? Bloating and flatus are not cardinal symptoms of serious conditions such as cancer, nor of diverticular disease, nor of inflammatory bowel disease(IBD). The exception is extensive small bowel disease, in which other symptoms usually predominate in any case.However, as mentioned earlier, malabsorptive conditions such as coeliac disease or enzyme deficiencies such as lactose intolerance may present in this way.* Assessment of the patient history The complaint first needs to be interpreted. Is `gas' a reference to belching or post- prandial reflux; is `wind' a synonym for abdominal discomfort or an unpleasant odour in flatus? Frequency of passing flatus is very variable between individuals, but fewer than 20 times per day is probably normal.There is also a gender difference, and according to a recent Australian study, men pass flatus twice as often as women.10One must also actively exclude indicators of serious bowel disease such as rectal bleeding, persistent change in bowel habit, nocturnal pain, weight loss, and family history of colo-rectal cancer or IBD.The additional parts of the history of relevance are stool characteristics and diet; the former is significant as floating stools are more indicative of methane trapping than of fat content.Steatorrhoea should lead to suspicion of malabsorption due perhaps to coeliac disease, pancreatic exocrine failure or bacterial overgrowth.Elements in the diet that may produce flatus and a bloated sensation, such as beans and onions, should be sought, but may be well known to the patient already. The performing `petomane' in one of the Spanish director Bigas Luna's recent films ate cauliflower in quantity to prepare for his act of producing tunes by passing flatus.Other less obvious fermentable carbohydrate sources include apples, apple juice, prunes and raisins, probably because of their slowly metabolised content of fructose and sorbitol - both of which are now also widely used as sweeteners - together with pectin (a constituent of plant cell-walls), nuts and chewing gum, which also leads to hypersalivation and aerophagia. Less troublesome vegetables include lettuce, cucumber, courgette and peppers.* Examination Bloating purely related to weight gain can be observed if the weight is checked, as it indicates one of the familiar five `F's used to explain abdominal distension to students - namely `fat'.The remaining `F's are `foetus', `fluid', `flatus' and `faeces'. These serve as a reminder, especially to check for shifting dullness if the bloating is constant and not clearly bowel related.Faeces may be palpable, especially in the left colon and should hold an indentation.`Faking' might be regarded as a sixth `F' that should also be considered. Some patients exaggerate the lumbar lordosis and so appear distended. However, lying them flat with an examining hand checking that the lumbar spine reaches the couch will reveal the lack of physical pathology. This is sometimes termed `pseudocyesis': spurious pregnancy.Commonly, however, the bloated patient is diffusely tender throughout the abdomen, and finding this is reassuring to a degree, as it eliminates serious local pathology where there is no mass and the patient looks otherwise well and symptoms are not new.It is easy to listen for a sucussion splash as evidence of gastric outflow obstruction, and this can be rewarding.Where sigmoidoscopy is conducted and the bloating sensation is reproduced on air insufflation, this is a useful discriminatory sign for IBS.* Investigation: flatulence and bloating As noted above, worrying signs and symptoms in the upper gastrointestinal tract or bowel that occur concurrently should be investigated formally by endoscopy or imaging.Bloating is a common complaint especially in women, and particularly in peri-menopausal women. There is no simultaneous serious condition co-existing in the vast majority, so investigation is not necessary.A normal blood count can be very reassuring where there is a suspicion of small bowel disease: symptomatic coeliacs will have anaemia; active Crohn's sufferers will have raised platelets with or without anaemia, and raised white cells; and a normal ESR similarly reduces the suspicion of an inflammatory component.If flatus is a source of real disruption a hydrogen breath test with ingestion of the particular carbohydrate suspected may reassure.* Treatment: bloating Reassurance that their condition is not serious is all some people need. Simple anti-constipating measures of fibre and sufficient fluid with daily exercise with or without anti-constipation agents is often successful.The first choice is probably fibre. Fibre has been related to gas production,10 but it may not be implicated as much as lactulose, which has been suggested as a reliable reference standard for this.Where the symptoms fit in with IBS, regimes for this may help,11 ranging from peppermint oil to promotility agents, and from anti-depressants (to reduce visceral sensation) to biofeedback.* Treatment: predominant flatulence Treat as with bloating. However, if the treatment approaches above fail the next step is exclusion diets in which one element is excluded at a time only.Lactose is present in a surprising variety of foods, and packets need to be checked. However, mature cheeses and 1-2 quarter cups of milk a day can often still be tolerated.12 Excluding the carbohydrates mentioned above, such as sorbitol, can lead to dramatic relief, and a review of medications may be helpful.Acarbose rates as a highly flatogenic compound13 as it is subject to fermentation, and constipating agents such as codeine together with calcium- antagonists are reported to cause significant amounts of bloating in some cases.* Treatment: belching Other than explanations and reassurance, stopping chewing gum and smoking should be recommended, as they can produce aerophagia together with advice to limit carbonated drinks.14The active ingredient in over-the-counter anti- wind treatment, simethicone theoretically allows coalescence of trapped gas particles so that they can escape. It works in a few patients.* Treatment: smell Charcoal has its enthusiasts and should theoretically work to reduce volatile sulphur compounds.Using gas- tight pantaloons incorporating charcoal impregnated cushions has been found to reduce the sulphur-containing content of escaping intestinal gas eleven-fold4 but oral charcoal is ineffective.15Dietary exclusion again plays a part by trial and error. Bolin found that when men rated their flatus it was more aromatic the day following an evening of beer-drinking.10 Other such correlations may only appear if a prospective diary is kept.It has been suggested that sulphate- reducing bacteria increase after antibiotics, and so there may be a role for introducing lactobacilli in an attempt to establish a more agreeable colony of bacteria - this is likely to be especially important if mankind proceeds to undertake long space trips to colonise other planets.* Summary Gas means different thing to different people and the complaint must be defined carefully. Belching is almost always due to aerophagia and anxiety, and this can be treated conventionally.Normal people produce gas from food by way of colonic bacteria. This is exaggerated in conditions like malabsorption.In the majority, however, bloating is due to altered sensation rather than volume. Understanding the mechanism allows one to explain the logic behind exclusion diets. Bloating is part of IBS, and treatment may follow similar lines especially treatment of constipation.Unpleasant odours result from trace quantities of sulphurous gas in the flatus. Individuals can learn which foods are troublesome in this respect.References1 Vishniac W, Favourite FG. Intestinal hydrogen and methane of men fed space diet. Life Sci and Space Res 1969;8:102-1092 Grimble G. Fibre, fermentation, flora and flatus (leading article). Gut 1989;30:6-33 Macfarlane GT & S. Human colonic microbiota: ecology, physiology and metabolic potential of intestinal bacteria. Scand J Gastroenterol 1997;32 suppl 222:3-94 Suarez FL, Springfield J, Levitt MD. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour. Gut 1998;43:100-1045 Bigard MA, Gaucher P, Lasalle C. Fatal colonic explosion during colonoscopic polypectomy. Gastroenterology 1979;77:13076 Calloway DH, Murphy EL. The use of expired air to measure intestinal gas formation. Ann NY Acad Sci 1968;150:82-957 Perman JA, Boatwright DN. Approach to the patient with gas and bloating. Chapter 37 in Yamada T. Textbook of Gastroenterology. Lippincott Williams and Wilkins, Philadelphia 1999.8 Lasser RB, Bond JH, Levitt MD. The role of intestinal gas in functional abdominal pain. N Engl J Med 1975;293(11):524-69 King TS, Elia M, Hunter JO. Abnormal colonic fermentation in irritable bowel syndrome. Lancet 1998;352:1187-8910 Bolin TD, Stanton RA. Flatus emissions patterns and fibre intake. Eur J Surg 1998;Suppl 582:115- 11811 Farthing MJ. New Drugs in the management of the irritable bowel syndrome. ( Review article) Drugs 1998;56(1):11-2112 Daniels CD. Untitled article on lactose intolerance. (Readable summary). Dig Health Nut 1999;Nov/Dec:18-2013 Lam KS, Tiu SC, Tsang MW, IpTP, Tam SC. Acarbose in NIDDM patients with poor control on conventional agents. Diabetes Care 1998;21(7):1154-814 Rao SSC. Belching, bloating and flatulence. Postgrad Med 1997;101(4):263-27815 Suarez FL, Furne J, Springfield J, Levitt MD. Failure of activated charcoal to reduce the release of gases produced by the colonic flora. Am J Gastroenterol 1999;94(1):208-212