Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 15-05: Gastrointestinal Gas + Key Features Download Section PDF Listen +++ ++ The rate and volume of expulsion of flatus is highly variable Healthy adults pass flatus up to 20 times daily and excrete up to 750 mL Flatus is derived from two sources Swallowed air (primarily nitrogen) Bacterial fermentation of undigested carbohydrate A number of short-chain carbohydrates ("FODMAPS") are incompletely absorbed in the small intestine and pass into the colon Lactose (dairy products) Fructose (fruits, corn syrups, and some sweeteners) Polyols (stone-fruits, mushrooms, and some sweeteners) Oligosaccharides (legumes, lentils, cruciferous vegetables, garlic, onion, pasta, and whole grains) Abnormal gas production may be caused by increased ingestion of these carbohydrates or, less commonly, by malabsorption disorders + Clinical Findings Download Section PDF Listen +++ ++ Chronic abdominal distention or bloating Many patients have an underlying functional gastrointestinal disorder such as irritable bowel syndrome or functional dyspepsia Constipation should be treated, and exercise (which accelerates gas propulsion) is recommended Organic causes of acute bloating with distention, vomiting, and pain include Ascites Gastrointestinal obstruction (gastric fundoplication, gastric outlet obstruction, small intestine or colon obstruction, and constipation) + Diagnosis Download Section PDF Listen +++ ++ Determining abnormal from normal amounts of flatus is difficult Lactose intolerance may be assessed by a 2-week trial of a lactose-free diet or by a hydrogen breath test + Treatment Download Section PDF Listen +++ ++ Conservative management for patients with a longstanding history of flatulence and no other symptoms or signs of malabsorption The nonprescription agent Beano (α-d-galactosidase enzyme) reduces gas caused by foods containing galacto-oligosaccharides (legumes, chickpeas, lentils) but not other FODMAPS Activated charcoal may afford relief Simethicone is of no benefit Probiotics may reduce flatus (anecdotal evidence) Medications that inhibit gastrointestinal motility should be avoided (opioids and calcium channel blockers)