Flatus & Bloating

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

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)

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

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)