INTRODUCTION — A variety of gastrointestinal complaints, such as belching, bloating, abdominal pain, and flatulence, are commonly attributed by the patient to "excess gas," even though this perception is usually incorrect. When excessive intestinal gas does occur, it may be due to excessive air swallowing, increased intraluminal production from malabsorbed nutrients, decreased gas absorption due to obstruction or dysfunctional gas clearance, or expansion of intraluminal gas due to changes in atmospheric pressure. This topic will review the evaluation and management of patients with predominant symptoms of belching, flatulence, abdominal bloating, and distension. Other functional gastrointestinal disorders associated with these symptoms are discussed in detail separately. (See "Clinical manifestations and diagnosis of irritable bowel syndrome in adults" and "Functional dyspepsia in adults" and "Etiology and evaluation of chronic constipation in adults", section on 'Etiology and pathophysiology'.)
PATHOPHYSIOLOGY
Volume and composition of intestinal gas — The understanding of intestinal gas syndromes has been aided by studies of intestinal gas composition and volume in asymptomatic individuals and in those with complaints of intestinal gas. The volume of gas in the intestinal tract is approximately 200 mL in both the fasting and postprandial states in both normal subjects and individuals who complain of gaseous distention [1-4]. Nitrogen (N2), oxygen (O2), carbon dioxide (CO2), hydrogen (H2), and methane (CH4) account for more than 99 percent of expelled intestinal gas [1]. The composition of gas within the intestinal tract is predominantly N2 [1]. Oxygen is present in very low concentrations, and the concentrations of CO2, H2, and CH4 vary among individuals.
The composition of gas also varies within sections of the gastrointestinal tract. As an example, stomach gas contains high concentrations of N2 and O2 similar to the atmosphere, while flatus contains less O2 and more CH4. None of the principal gases has an odor. Minor constituents of flatus, to which odor may be attributable, include sulfur-containing compounds such as methanethiol, dimethyl sulfide, hydrogen sulfide, as well as short-chain fatty acids, skatoles, indoles, volatile amines, and ammonia [5,6].
Sources of intestinal gas
Air swallowing — Air swallowing (aerophagia) is the major source of stomach gas. Several milliliters of air are ingested in each normal swallow. Larger amounts are swallowed when food is gulped. Aerophagia can be a manifestation of anxiety, and is increased with gum chewing and smoking. Most swallowed air appears to be eructated [7].
Swallowed air is the major source of O2 and N2 in intestinal gas. Posture may influence the amount of swallowed air passing from the stomach into the small intestine. The supine position causes gastric air to pass preferentially into the small intestine as gastric air is located above liquid gastric contents that overlie the gastroesophageal junction.
Intraluminal production — Three of the five principal gases, CO2, H2, and CH4, are produced within the bowel lumen.
●CO2 – CO2 is derived from digestion of fat and protein in the upper gastrointestinal tract, from bacterial fermentation of intraluminal substrates, or may be liberated from the interaction of acid and bicarbonate [8]. Much of the CO2 produced in the upper small intestine is probably absorbed before it reaches the colon. CO2 that is present in flatus is likely due to bacterial fermentation reactions in the colon. Increased CO2 in flatus can result from specific dietary substrates, such as nondigestible carbohydrates [9].
●H2 – H2 is both produced and consumed by fecal bacteria; the net H2 excretion is determined by these two processes. H2 production occurs predominantly in the colon [10]. Ingested carbohydrate and protein are sources for H2 production. In healthy individuals, certain foods with high concentrations of oligosaccharides, such as stachyose and raffinose found in legumes, or resistant starches (flours made from wheat, oats, potatoes, and corn), cannot be completely digested by enzymes within the normal small bowel, leading to increased H2 production [11]. H2 consumption occurs in the bacterial production of CH4, sulfide, and acetate [12-14]. H2 is excreted in the breath (after absorption into the bloodstream) or passed in flatus.
Small intestinal carbohydrate malabsorption leads to increased delivery of carbohydrates to the colon and increased H2 gas production. Increased colonic H2 production following carbohydrate ingestion forms the basis for the H2 breath test for carbohydrate malabsorption [15]. (See "Approach to the adult patient with suspected malabsorption", section on 'Breath tests'.)
●Methane – Methane, like H2, is exclusively a product of bacterial metabolism. The principal methanogen is Methanobrevibacter smithii. Because M. smithii catalyzes the reaction: 4H2 + CO2 --> CH4 + 2H20, it reduces the volume of gas that would otherwise be present in the colon. CH4 may be absorbed into the portal circulation and excreted in expired air, or excreted in flatus.
The tendency to produce CH4 is determined by the concentration of methanogens in the colon, and may be related to genetic or environmental factors. The presence of bile acid in the colon also may be important in the regulation of methanogenesis [16].
Diffusion from the blood — The partial pressure of intestinal gases determines the direction of diffusion of the gas between the intestinal lumen and the bloodstream.
●H2 and CH4 have high partial pressures in the intestinal lumen as compared with the bloodstream and therefore diffuse readily out of the intestine.
●Gastric luminal oxygen is absorbed into the bloodstream since it has a relatively high partial pressure (due to its concentration in swallowed air). On the other hand, colonic luminal oxygen has a low partial pressure; it tends to diffuse from the blood into the lumen.
●CO2 has a variable pattern of diffusion. The partial pressure of CO2 in the gastric lumen is lower than that of the blood; thus, CO2 tends to diffuse into the gastric lumen. As it reaches the duodenum, the partial pressure of CO2 becomes higher in the lumen than in the bloodstream, and its direction of diffusion reverses.
●N2 has a relatively high partial pressure in the stomach with resultant diffusion into the blood, but its partial pressure falls below that of the blood in the duodenum, and the direction of diffusion reverses.
Causes of increased intestinal gas — When excessive intestinal gas occurs, it may be due to excessive air swallowing, increased intraluminal production from malabsorbed nutrients, decreased gas absorption due to obstruction, or expansion of intraluminal gas due to changes in atmospheric pressure (table 1). (See "Overview of nutrient absorption and etiopathogenesis of malabsorption".)
BELCHING
Terminology — Belching or eructation is defined as an audible escape of air from the esophagus or the stomach into the pharynx [17]. It may be voluntary or involuntary. Involuntary belching typically follows a meal and is caused by the release of swallowed air after gastric distention. Belching is only considered a disorder when it is excessive and becomes troublesome.
Etiology and pathogenesis — Depending on the origin of the refluxed gas, belching is classified into two types:
●Supragastric belching – Eructated air does not originate from the stomach and is expelled air from the esophagus. Cineradiography studies have demonstrated that patients relax their upper esophageal sphincter, swallow air, and then release it from the esophagus before it reaches the stomach [18]. Some patients achieve this by creating a negative intrathoracic pressure, possibly by inspiring against a closed glottis, and then relaxing the upper esophageal sphincter to allow air to enter the esophagus. Others force air into their esophagus by simultaneously contracting the muscles of their pharynx, palate, and tongue [19].
●Gastric belching – A gastric belch is characterized by the escape of swallowed intragastric air that enters the esophagus during a transient lower-esophageal sphincter relaxation. Gastric belching may be facilitated by foods that relax the lower esophageal sphincter, such as chocolate, fats, and mints [20]. Gastric belches occur 25 to 30 times per day and are usually physiological and involuntary.
Individuals with belching disorder usually have habitual air swallowing (aerophagia) and air may transit only to the esophagus before being vented (supragastric belching). In these patients, belching frequently becomes habitual and may be incorrectly regarded as being indicative of an underlying gastrointestinal disease.
In patients with isolated symptoms of excessive belching, psychological and behavioral factors play an important role. Belches typically increase when patients are aware they are being observed and are almost absent during sleep. Patients presenting with excessive belching as their main symptom usually have an increased frequency of supragastric belches.
Belching is also associated with gastroesophageal reflux disease (GERD) and functional dyspepsia. However, in patients with GERD and functional dyspepsia, belching is not the predominant symptom. Supragastric belching can cause acid reflux in some cases and in others may be a response to an unpleasant esophageal sensation induced by an episode of reflux [21]. (See "Clinical manifestations and diagnosis of gastroesophageal reflux in adults", section on 'Patients without classic symptoms'.)
Diagnostic approach
Evaluation — Belching disorder is a functional syndrome, and the diagnosis is based on a history. Observation of air swallowing provides supportive information. Patients who complain of isolated excessive belching are more likely to suffer from excessive uncontrolled supragastric belching, and from episodes of frequent belching in which they may belch up to 20 times per minute.
The presence of alarm features including weight loss, abdominal pain, dysphagia, heartburn, and regurgitation are an indication for further diagnostic evaluation with upper endoscopy and/or imaging (eg, abdominal computed tomography (CT) scan).
Diagnostic criteria for functional belching — According to the Rome IV criteria, belching disorder is defined as bothersome (ie, severe enough to impact usual activities) belching from the esophagus or stomach more than three days a week [22]. These criteria should be fulfilled for the last three months with symptom onset at least six months before diagnosis.
The diagnosis of supragastric belching is supported by observing frequent, repetitive belching, but gastric belching has no established clinical correlate. Objective intraluminal impedance measurement can be used to distinguish supragastric from gastric belching.
Management
●Education, treatment of associated disorders, and behavioral therapy – Management includes education to decrease air swallowing and reassurance that belching is a benign condition. Specific behavioral measures include discontinuation of gum chewing, smoking, drinking carbonated beverages, and gulping foods and liquids. In patients with underlying depression or anxiety, treatment should be initiated [23]. Patients with co-existing acid reflux may require acid suppressive therapy for management of GERD. (See "Medical management of gastroesophageal reflux disease in adults", section on 'Subsequent management'.)
Successful treatment of excessive belching by a therapist (eg, cognitive behavioral therapist or speech therapist) with special training in diaphragmatic breathing techniques has been associated with a reduction in symptoms in small observational studies (figure 1) [24,25]. Diaphragmatic breathing reduces postprandial intragastric pressure and increases esophagogastric junction zone pressure, restoring the gastroesophageal pressure gradient.
●Reflux inhibitors for refractory symptoms – Baclofen (10 mg three times daily) by reducing transient lower esophageal sphincter relaxations and centrally suppressing the swallowing rate, may decrease both supragastric and gastric belching. However, given the side-effects of baclofen, we reserve its use for patients in whom other approaches have been unsuccessful [26].
FLATULENCE — The volume of gas passed per rectum varies from about 500 to 1500 mL per day [3]. The frequency of flatus released varies between 10 and 20 times per day in healthy subjects [27]. Most individuals who report excessive flatulence fall within this range.
Etiology and pathogenesis — Although excessive passage of flatus or its foul odor may be a source of embarrassment to the patient, it is rarely associated with serious illness. Offensive odor, when present, may be due to sulfur-containing compounds, such as methanethiol, dimethyl sulfide, and hydrogen sulfide, as well as short-chain fatty acids, skatoles, indoles, volatile amines, and ammonia.
A number of factors may account for bothersome flatus:
●An alteration of intestinal motility or intestinal bacteria.
●Dietary factors, such as an increased intake of lactose, fructose, sorbitol; undigestible starches in fruits, vegetables, and legumes; and carbonated beverages. Products such as pork may release trace concentrations of malodorous gases upon digestion (table 2).
●Psychological factors may cause a heightened sensitivity to normal flatal passage.
Diagnostic evaluation — Evaluation of the patient complaining of flatulence should be guided by the history and physical examination. A dietary history should be obtained with a focus on gas-producing foods and beverages (table 2).
Alarm features — Alarm features in patients with flatulence include the following:
●Nocturnal abdominal pain
●Weight loss
●Hematochezia
●Systemic symptoms including weight loss or fever
●Diarrhea or steatorrhea
●Vomiting
●Severe abdominal tenderness, organomegaly, or succussion splash on physical examination
Additional evaluation for patients with flatulence depends on the presence of alarm features (table 3). As an example, new onset of flatulence associated with alarm symptoms such as diarrhea and abdominal pain should be evaluated for malabsorption. This may include stool examination for fat and Giardia, breath tests for small intestinal and lactose intolerance, celiac serology, and endoscopic evaluation. In the absence of alarm features, we do not perform any additional evaluation. (See "Approach to the adult patient with suspected malabsorption".)
Management — Several measures that can be undertaken to reduce flatulence include:
●Treatment of the underlying cause – In individuals with lactose intolerance, management includes lactose restriction and the use of enzyme preparations that are taken orally with lactose-containing foods. In patients with small bowel bacterial overgrowth, treatment is with antibiotic therapy. (See "Small intestinal bacterial overgrowth: Management" and "Lactose intolerance and malabsorption: Clinical manifestations, diagnosis, and management", section on 'Management'.)
●Dietary modification – Patients should be advised to avoid gas-producing foods (eg, beans, cabbage, onions, broccoli, brussel sprouts, wheat, and potatoes) and note if symptoms improve. In patients without a significant improvement despite exclusion of gas-producing foods, we suggest a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) (table 4) [28,29]. FODMAP dietary education should be provided by a trained dietician to avoid dietary over-restriction and a nutritionally replete diet. (See "Treatment of irritable bowel syndrome in adults", section on 'Low FODMAP diet'.)
●Other interventions – Other interventions that have not consistently demonstrated efficacy in the prevention or management of flatulence include anti-flatulence medications (eg, simethicone and activated charcoal) and alpha-galactosidase enzyme preparation. We therefore do not advocate their use [30-36].
Bismuth subsalicylate reduces the odor arising from hydrogen sulfide as well as other pungent components of flatus [37]. However, long-term administration is associated with potential toxicity. External devices to deodorize flatus (eg, charcoal-lined underwear, cushions) are commercially available but their efficacy has not been well established [6,38].
ABDOMINAL BLOATING AND DISTENSION — Bloating refers to a sensation of abdominal fullness, pressure, or a sensation of trapped gas, whereas distension is a measurable increase in abdominal girth. Other causes of abdominal girth include ascites, abdominal obesity, giant ovarian or mesenteric cyst, and bowel obstruction (mechanical or functional). These entities can typically be differentiated based on physical examination findings and if uncertain, abdominal imaging. (See "Evaluation of adults with ascites", section on 'Differential diagnosis'.)
Bloating and distension have been reported in 20 to 30 percent of the general population and in up to 96 percent of patients with irritable bowel syndrome (IBS) [39-41].
Etiopathogenesis — Bloating and distension due to intestinal gas may be due an organic etiology that results in excessive intestinal gas (eg, small intestinal bacterial overgrowth, celiac disease, lactose intolerance) or a functional gastrointestinal disorder (table 5). Functional disorders associated with bloating and distension include IBS or functional constipation, functional diarrhea, or functional abdominal bloating/distention.
The pathogenesis of abdominal bloating is incompletely understood and is likely to be multifactorial. Determinants of abdominal bloating include the amount and type of intestinal gas present, osmotic, and water content in the lumen, gut microbiota, motility and transit times, and alterations in visceral sensitivity.
The feeling of abdominal bloating is often attributed to excessive gas by patients. However, the relationship between the amount of intestinal gas and symptoms is not straightforward. In one study, the composition and average volume of intestinal gas in patients with complaints of chronic gaseousness and controls was similar (176 and 199 mL, respectively) [42]. Radiographic studies with plain films and CT have also shown no evidence of increased gas in patients complaining of gaseous distension [43], although discordant data have also been reported [4]. Impaired transit of intestinal gas may be responsible for symptoms of bloating and distension in some patients [44-49].
Other studies have suggested that patients with chronic complaints of bloating and distension have heightened sensitivity to gaseous distension or an exaggerated motor response to normal amounts of gas [3,50,51]. The gut microbiota has also been implicated in the pathophysiology of abdominal bloating [52]. Mechanisms of gut dysfunction may involve dysbiosis of the gut microbiota by interactions with epithelium, immune system, enteric nervous system, and central nervous system [53]. (See "Pathophysiology of irritable bowel syndrome".)
A proposed mechanism for abdominal distension is incoordination of the abdomino-phrenic reflex. Investigators found that subjects with bloating and distention respond to modest increases in intraluminal gas by evidencing downward rather than upward displacement of their diaphragm, resulting in visible protrusion of the anterior abdominal wall [43,54]. In contrast, patients with measurable gut dysmotility harbor larger volumes of intraluminal gas during bloating episodes, resulting in excessive abdominal bulging despite normal cephalic displacement of the diaphragm [55]. The mechanism underlying the disordered reflex has not been elucidated.
Evaluation — Bloating and distension may be caused by organic disease or other functional gastrointestinal disorders. A clinical diagnosis of functional bloating/distension requires the fulfillment of symptom-based diagnostic criteria and a limited evaluation to exclude underlying organic disease.
●History and physical examination – The evaluation of a patient with abdominal bloating and/or distention should begin with a history and physical examination to determine the underlying cause and to identify patients with alarm features (table 3).
History should include the onset of symptoms, the relationship to diet (eg, wheat, dairy, fructose, fiber, nonabsorbable sugars) diurnal variation, and the presence of symptoms suggestive of other functional gastrointestinal disorders, including constipation, diarrhea, and abdominal pain or post-prandial fullness.
Functional bloating usually exhibits a diurnal pattern [56]. It may follow ingestion of specific foods and sometimes be accompanied by excessive burping or flatus (but these may be unrelated to the sensation of bloating). Patients may complain of worsening of symptoms as the day progresses, particularly after meals, but alleviation of symptoms overnight.
Patients with functional bloating may have mild pain related to bloating as well as minor bowel movement abnormalities, but unlike other functional gastrointestinal disorders (eg, irritable bowel syndrome, functional constipation, functional dyspepsia), abdominal pain or abnormalities in bowel movements are not the predominant symptom.
●Initial testing – We perform a limited evaluation in patients with symptoms of bloating and/or distention, including a complete blood count to evaluate for anemia and serologies for celiac sprue. In addition, we perform a breath test for small intestinal bacterial overgrowth. Testing for lactose intolerance should be performed if symptoms occur with significant lactose ingestion. New, persistent bloating in middle-aged or older women (or those with an abnormal pelvic examination) should prompt pelvic imaging (eg, ultrasound) to rule out ovarian cancer. (See "Epithelial carcinoma of the ovary, fallopian tube, and peritoneum: Clinical features and diagnosis", section on 'Diagnostic evaluation'.)
●Additional evaluation in selected patients – Additional evaluation is reserved for patients with alarm features or abnormal initial testing. The evaluation is based on their clinical presentation and features. As an example, in patients with alarm features, such as anemia, diarrhea, or unintentional weight loss, we perform endoscopic evaluation and pancreatic imaging as symptoms may be evidence of a malabsorptive process (table 3). The evaluation of patients with suspected malabsorption is discussed in detail separately. (See "Approach to the adult patient with suspected malabsorption".)
Diagnostic criteria for functional bloating/distension — Rome IV criteria for establishing the diagnosis of functional bloating include both of the following (for at least three months with symptom onset at least six months prior to diagnosis) [57].
●Recurrent bloating or distension, on average, at least one day per week; abdominal bloating and/or distension predominates over other symptoms
●Insufficient criteria for a diagnosis of IBS, functional constipation, functional diarrhea, or postprandial distress syndrome
Mild pain related to bloating may be present as well as minor bowel movement abnormalities. (See "Etiology and evaluation of chronic constipation in adults", section on 'Definition of constipation' and "Clinical manifestations and diagnosis of irritable bowel syndrome in adults", section on 'Diagnostic criteria' and "Functional dyspepsia in adults", section on 'Diagnostic criteria'.)
Management
●Dietary and lifestyle modification – Approach to treatment of abdominal bloating and distension is similar to that used in patients with IBS. Patients are advised to avoid foods that increase flatulence (eg, beans, onions, celery, carrots, raisins, bananas, apricots, prunes, Brussels sprouts, wheat germ, pretzels, and bagels). We suggest a diet low in FODMAPs in patients with persistent symptoms despite exclusion of gas-producing foods (table 4). Other dietary modifications that may be helpful include restriction of carbonated drinks. Mild exercise and erect posture may improve bloating in some patients [58-60]. (See 'Management' above and "Treatment of irritable bowel syndrome in adults", section on 'Low FODMAP diet'.)
●Treatment of the underlying cause – In patients with small intestinal bacterial overgrowth antibiotic treatment is indicated. In individuals with lactose intolerance, management includes lactose restriction and the use of oral enzyme preparations with lactose-containing foods. Anticholinergic agents, opioids, and calcium blockers should be avoided because of their effects on gut motility. (See "Small intestinal bacterial overgrowth: Management" and "Lactose intolerance and malabsorption: Clinical manifestations, diagnosis, and management", section on 'Management'.)
●Biofeedback – In patients with functional abdominal distension, biofeedback may decrease distension. In an observational study that included 45 patients with functional gastrointestinal disorders associated with distension, 15 individuals who received electromyography (EMG)-guided respiratory biofeedback had significantly lower rates of abdominal distension as compared with controls [61]. EMG activity of the intercostals and diaphragm significantly decreased after biofeedback, while activity of the abdominal muscles, particularly the internal oblique, significantly increased.
●Other therapies – Other therapies lacking clear evidence of efficacy in decreasing bloating/distension include antifoaming agents (eg, simethicone), adsorbents (eg, activated charcoal), and probiotics [30]. Although probiotics have been associated with an improvement in symptoms in patients with IBS, the magnitude of benefit and the most effective species and strain are uncertain. (See "Treatment of irritable bowel syndrome in adults", section on 'Probiotics'.)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Gas and bloating (The Basics)")
●Beyond the Basics topics (see "Patient education: Lactose intolerance (The Basics)" and "Patient education: Gas and bloating (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Intestinal gas volume and composition – The volume of gas in the intestinal tract is approximately 200 mL in both the fasting and postprandial states in both normal subjects and individuals who complain of gaseous distension. Nitrogen, oxygen, carbon dioxide, hydrogen, and methane account for more that 99 percent of expelled intestinal gas. (See 'Volume and composition of intestinal gas' above.)
●Etiology of excessive intestinal gas – When excessive intestinal gas occurs, it may be due to conditions associated with excessive air swallowing, increased intraluminal production from malabsorbed nutrients, decreased gas absorption due to obstruction, or expansion of intraluminal gas due to changes in atmospheric pressure (table 1). (See 'Sources of intestinal gas' above.)
●Belching or eructation
•Definition – Belching is defined as an audible escape of air from the esophagus or the stomach into the pharynx. It may be voluntary or involuntary. Involuntary belching typically follows a meal and is caused by the release of swallowed air after gastric distention. Belching is only considered a disorder when it is excessive and becomes troublesome. Belching disorder is a functional syndrome and the diagnosis is based on a history.
•Indications for evaluation – The presence of alarm features including weight loss, abdominal pain, dysphagia, heartburn, and regurgitation are an indication for further diagnostic evaluation with upper endoscopy and/or imaging (eg, abdominal computed tomography scan) to rule out other etiologies. (See 'Belching' above.)
•Management of belching
-Behavioral changes – In patients who complain predominantly of belching, we suggest behavioral changes (Grade 2C). Specific measures include diaphragmatic breathing and discontinuation of gum chewing, smoking, drinking carbonated beverages, and gulping foods and liquids (figure 1).
-Treatment of associated conditions – In patients with underlying depression or anxiety, treatment should be initiated. Patients with co-existing acid reflux may require acid-suppressive therapy for management of gastroesophageal reflux disease.
-Refractory symptoms – We reserve the use of baclofen for patients in whom other approaches have been unsuccessful. (See 'Management' above.)
●Bloating
•Etiology – Bloating refers to a sensation of abdominal fullness, pressure, or a sensation of trapped gas, whereas distension is a measurable increase in abdominal girth. Bloating and distension due to intestinal gas may be due an organic etiology that results in excessive intestinal gas (eg, small intestinal bacterial overgrowth, celiac disease, lactose intolerance) or a functional gastrointestinal disorder.
•Evaluation – Initial evaluation of a patient with abdominal bloating and/or distention includes a history and physical examination to identify alarm features (table 3), and limited diagnostic testing (complete blood count, celiac serologies, breath tests for small intestinal bacterial overgrowth). Additional evaluation is reserved for patients with alarm features or abnormal initial testing. (See 'Abdominal bloating and distension' above.)
●Flatulence
•Evaluation – Although excessive passage of flatus or its foul odor may be a source of embarrassment to the patient, it is rarely associated with serious illness. Initial evaluation of the patient complaining of flatulence should be guided by the history and physical examination. A dietary history should be taken and focused on gas-producing foods and beverages. The goal is to identify alarm features that are suggestive of malabsorption or a colorectal malignancy, which will direct the diagnostic approach. Additional evaluation for patients with flatulence depends on the presence of associated alarm features and the specific alarm sign/symptom (table 3). In the absence of alarm features, we do not perform additional evaluation. (See 'Etiology and pathogenesis' above and 'Diagnostic evaluation' above.)
•Management
-Dietary measures – In patients who complain predominantly of flatulence or bloating, we suggest dietary changes (Grade 2C). Patients should be advised to avoid gas-producing foods (eg, cabbage, legumes, onions, broccoli, brussel sprouts, wheat, and potatoes). In patients without a significant improvement despite exclusion of gas-producing foods, we suggest a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (table 4).
-Address the underlying etiology – In patients with an underlying cause (eg, small intestinal bacterial overgrowth, lactose intolerance), this should be concurrently addressed. (See 'Management' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff thank Dr. Stephen E. Goldfinger for his past contributions as an author to this topic review.
