Increased levels associated with passing flatus more than 22 times per day and is caused by malabsorption of carbohydrates associated with celiac sprue, pancreatic insufficiency, short bowel syndrome, malabsorption of lactose, fructose, sorbitol and starch.

Associated with colonic bacterial fermentation of unabsorbed carbohydrates.

Occasional flatulence and belching after meals is not abnormal, the symptoms could be bothersome, particularly when they occur in excess.

Flatulence is defined in the medical literature as flatus expelled through the anus.

Flatus is also the medical word for gas generated in the stomach or bowels.

A proportion of intestinal gas may be swallowed environmental air, and hence flatus is not totally generated in the stomach or bowels.

It is normal for humans to pass flatus through the rectum.

The volume and frequency of flatus may vary greatly between individuals.

Intestinal gas passed through the rectum has a characteristic feculent smell, that may vary in concentration.

Flatus is brought to the rectum by muscle contractions in the intestines and colon.

The noises associated with flatulence are caused by the vibration of anal sphincters.

Symptoms related to intestinal gas include: pain, bloating and abdominal distension, excessive flatus volume, excessive flatus smell and gas incontinence.

Eructation is sometimes included under the topic of flatulence.

When excessive or malodorous, flatus can be a sign of a health disorder, such as irritable bowel syndrome, celiac disease or lactose intolerance.

Derived terms include vaginal flatulence, otherwise known as a queef.

There are four different types of complaints that relate to intestinal gas.

Flatus, intestinal gas, is mostly produced as a byproduct of bacterial fermentation in the gastrointestinal (GI) tract, especially the colon

Bloating and pain, excessive volume, odor, and incontinence of flatus.

Patients with bloating frequently have objective increases in abdominal girth, often increased throughout the day and then resolved during sleep.

The distribution of intestinal gas in patients with bloating is not distributed normally in these patients.

With bloating there was segmental gas pooling and focal distension.

Abdominal distension, pain and bloating symptoms are the result of abnormal intestinal gas dynamics rather than increased flatus production.

The normal range of volumes of flatus in normal individuals is wide, 476–1,491 ml/24 h).

All intestinal gas is either swallowed environmental air, present intrinsically in foods and beverages, or the result of gut fermentation.

Intestinal gas is composed of varying quantities of exogenous sources and endogenous sources.

The exogenous gases are swallowed, aerophagia, when eating or drinking or increased swallowing during times of excessive salivation.

The endogenous gases are produced either as a by-product of digesting certain types of food, or of incomplete digestion, as is the case during steatorrhea.

While eating/drinking small amounts of air are swallowed, which is emitted from the mouth by burping and is normal.

Aerophagia, excessive swallowing of environmental air, rarely can be responsible for increased flatus volume.

Patients who have excessive intestinal gas that is mostly composed of nitrogen have aerophagia.

Gases contained in food and beverages are likewise emitted largely through eructation.

Intestinal gas that is endogenously produced makes up 74 percent of flatus in normal subjects.

The volume of gas produced is partially dependent upon the composition of the intestinal microbiota.

The intestinal microbiota varies significantly among different individuals.

Increased endogenous gas production may be due to gut microbiota.

The greatest concentration of gut bacteria is in the colon, while the small intestine is normally near sterile.

Fermentation occurs when unabsorbed food residues arrive in the colon.

Diet is the primary factor that dictates the volume of flatus produced, even more than the composition of the microbiota.

One can significantly reduce the volume of flatus produced, by reducing the amount of undigested fermentable food residues arriving in the colon

The presence of increased volume of intestinal gas does not cause bloating and pain in normal subjects.

It is abnormal intestinal gas dynamics that creates pain, distension, and bloating, regardless of whether there is high or low total flatus volume.

Flatus possesses odor, that may be abnormally increased in some patients.

The incontinence of gas refers to loss of voluntary control over the passage of flatus.

Gas incontinence is a type of fecal incontinence related to minor disruptions of the continence mechanisms.

Foods that are incompletely digested by the stomach or small intestine may cause flatulence when the material arrives in the large intestine, due to fermentation by yeast or prokaryotes normally or abnormally present in the large intestine.

Polysaccharides, especially oligosaccharides such as inulin produce flatulence.

Such foods include beans, lentils, dairy products, onions, garlic, spring onions, leeks, turnips, swedes, radishes, sweet potatoes, potatoes, cashews, Jerusalem artichokes, oats, wheat, yeast, cauliflower, broccoli, cabbage, Brussels sprouts and other cruciferous vegetables that belong to the genus Brassica are commonly reputed to not only increase flatulence, but to increase the pungency of the flatus.

Endogenous gases from beans seem to arise from complex oligosaccharides that are resistant to digestion, but are readily digestible by gut flora microorganisms.

Such oligosaccharides pass through the upper intestine largely unchanged, and when they reach the lower intestine, bacteria produce copious amounts of flatus.

Certain medicines, such as ibuprofen, laxatives, antifungal medicines or statins can cause excessive or malodorous flatus.

Giardiasis is associated with flatulence.

More than 99% of the volume of flatus is composed of non-smelling gases: oxygen, nitrogen, carbon dioxide, hydrogen and methane.

Nitrogen is not produced in the gut, but a component of environmental air.

Hydrogen, carbon dioxide and methane are produced in the intestine and make up 74% of the volume of flatus in normal subjects.

Methane and hydrogen are flammable, and can be ignited.

Not everyone produces flatus that contains methane.

The prevalence of methane over hydrogen in flatus may correlate with obesity, constipation and irritable bowel syndrome.

Archaea that oxidise hydrogen into methane promote the ability to absorb fatty acids from food.

It is the remaining trace compounds making up less than 1% of volume, that give flatus its smell.

The major contribution to the smell of flatus comes from a combination of volatile sulfur compounds.

Hydrogen sulfide, methyl mercaptan, dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide are present in flatus, and their stool concentration is correlated with bad smell of flatus.

Increased dietary sulfur-containing amino acids increases the smell of flatus, as it is likely that the smell of flatus is created by a combination of volatile sulfur compounds, with minimal contribution from non-sulfur volatiles.

Enhanced smell can also be caused by the presence of large numbers of microflora bacteria or the presence of stool in the rectum.

High diet protein, especially sulfur-containing amino acids significantly increase the smell of flatus.

Normal flatus volume range is around 476 to 1,491 ml per 24 hours.

Flatulence volume varies to a great extent upon diet.

The number of flatus episodes per day is 8–20 per day.

The mouth volume of flatus associated with each flatulence event again varies from 5–375 ml).

The initial volume of flatus passed upon wakening is significantly larger than episodes during the day: due to buildup of intestinal gas in the colon during sleep, and the peak in peristaltic activity in the first few hours after waking.

Intestinal gas moves independently of solids and liquids.

Intestinal gas moves more efficiently in the erect position compared to when supine.

Sensory nerve endings in the anal canal role may be to distinguish between flatus and feces helping detect a need to defecate or to signal the end of defecation.

Flatus generated sound varies with the tightness of the sphincter muscle and velocity of the gas being propelled.

Flatulence occasionally occurs incidentally to coughing, sneezing or during orgasm.

Fatulence can be voluntarily produced by bearing down on stomach or bowel muscles and relaxing the anal sphincter, resulting in the expulsion of flatus.

Agents that lower surface tension, known as surfactants, can reduce the sensations associated with flatulence, by aiding the dissolution of the gases into liquid and solid fecal matter.

Surfactants do not affect the production of the gases themselves,

Simethicone agents operate by promoting the coalescence of smaller bubbles into larger ones allowing them to be more easily passed from the body, either by burping or flatulence.

It does not decrease the total amount of gas generated in or passed from the colon.

Prokinetic agents, lubiprostone, antibiotics and probiotics are also used to treat bloating in patients with functional bowel disorders such as irritable bowel syndrome.

A rectal tube can be used to collect intestinal gas in a flatus bag.

By reducing the amount of fermentable carbohydrates, the low FODMAP diet (low fermentable oligosaccharide, disacharide, monosaccharide and polyols) can reduce the amount of flatus.

Most starches, including potatoes, corn, noodles, and wheat, produce gas as they are broken down in the large intestine.

Spices reported to counteract the production of intestinal gas include: cumin, coriander, caraway, fennel, and turmeric.

Fermenting beans, can make them less gas-inducing.

Fermentative lactic acid bacteria such as Lactobacillus casei and Lactobacillus plantarum reduce flatulence in human intestinal tract.

Probiotics are proposed to reduce flatulence when used to restore balance to the normal intestinal flora.

Bioactive yogurt contains, among other lactic bacteria, Lactobacillus acidophilus, which may be useful in reducing flatulence.

Prebiotics, are non-digestible oligosaccharides, increase flatulence.

Digestive enzyme supplements may reduce the amount of flatulence caused by some components of foods not being digested by the body.

Such digestive enzymes promote the action of microbes in the intestines: alpha-galactosidase enzymes, which can digest certain complex sugars, can reducing the volume and frequency of flatus.

The antibiotic rifaximin, often used to treat diarrhea may reduce both the production of intestinal gas and the frequency of flatus events.

Odor from flatulence is commonly treated with bismuth, and is commonly used by individuals who have had ostomy surgery, bariatric surgery, fecal incontinence and irritable bowel syndrome.

Bismuth subsalicylate binds hydrogen sulfide.

Activated charcoal does not produce reduction in both the total flatus volume nor the release of sulfur-containing gasses, in some studies.

Other studies suggest activated charcoal reduced hydrogen sulfide levels by 71%, and prevents a large increase in the number of flatus events and increased breath hydrogen concentrations that normally occur following a gas-producing meal.

Flatus incontinence occurs where there is involuntary passage of gas

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