The digestive processes in the gut continuously give rise to gaseous byproducts. These gaseous byproducts continue to build up in the gut till they are expelled forcefully through either belching or flatus. Belching is a forceful expulsion of gas produced in the upper gut through the oral cavity. Flatus is the gas that passes out through the anal canal. This is typically the gas that builds up in the lower gut and has an offensive odor. Flatulence refers to a condition in which gas production in the gut is excessive, leading to uncontrolled passing of flatus.
Even though passing gas is a normal physiological process that occurs in every individual, passing gas in public is usually a source of embarrassment. Under normal circumstances, one is able to sense the presence of flatus in the rectum and is able to hold off passing gas till the setting is appropriate. However, some individuals are unable to do so, leading to awkwardness in social settings. Flatulence may be serious enough in such cases to cause depression and anxiety.
Flatus may either pass out silently or with a loud noise. The sound that accompanies the passage of flatus is mainly caused by the passing of gas through the narrow anal sphincter. A part of the sound may also be due to the passage of gas through the buttocks. The sounds produced by the passage of flatus have been broadly classified into four distinct types: silent or slider type, staccato, open sphincter type, and bark type. The loudness of the sound depends on the volume of flatus released and the force with which the flatus escapes through the anal sphincter.
Sources of Flatus
The following are the main sources of flatus in the gut:
- Air that gets swallowed through the mouth.
- Gas present in carbonated beverages.
- Gaseous byproducts of chemical processes that aid the digestion of food.
- Diffusion of gas from the blood into the gut.
- Gaseous byproducts of bacterial action on food present in the gut.
Under normal circumstances, less than 200 mL of gas is present in the gut at all times. The majority of this gas comes from the action of intestinal bacteria that reside in the colon and act on the digested food components that pass through this region. Around 75% of the total volume of flatus is contributed by the action of these intestinal bacteria (also referred to as the gut flora).
Read more on excessive gas in the gut.
The population of these gut bacteria is usually kept in check through various mechanisms. An increase or imbalance in the population of these gut flora (in certain diseases) can lead to increased flatulence. The main gases produced by the bacterial decomposition of food in the gut are methane, hydrogen sulfide, and carbon dioxide. The foul odor of the flatus is mainly due to the presence of hydrogen sulfide in it.
Mechanism of normal control of flatus
The act of controlling the expulsion of flatus is similar to the act of controlling defecation. Both stools and flatus become perceptible when they fill up the rectum, and trigger an urge to expel them. This urge is caused by the stretching of the walls of the rectum due to the feces or the flatus. The anal opening is guarded by an external anal sphincter and an internal anal sphincter.
The external anal sphincter is under voluntary control. However, the internal anal sphincter is not under voluntary control. The internal anal sphincter relaxes once the pressure in the rectum increases to a certain level. But the flatus and feces cannot pass out as long as a person keeps the external anal sphincter closed. However, one cannot keep the external anal sphincter closed voluntarily for a long period since the act becomes very uncomfortable. Once an appropriate setting is found, relaxing the external anal sphincter allows the feces and flatus to pass out.
Symptoms of Uncontrollable Flatulence
Despite the exercise of voluntary control over the external anal sphincter, flatulence may become uncontrollable in some cases. Uncontrolled flatulence may be a symptom of an underlying disease. In some cases, it may be the only symptom. In other cases, the following symptoms may accompany uncontrollable flatulence:
- Fecal incontinence
- Itching in the anal region
- Abdominal bloating
- Perianal infections
- Bad body odor
Causes of Uncontrollable Flatulence
Uncontrollable flatulence is caused mainly due to an excessive production of gas in the gut and incontinence due to weak control over the external anal sphincter.
Excessive production of flatus
Excessive production of gas can occur due to a variety of factors. One of the most common causes of excessive flatulence is consumption of certain foods such as beans, apples, lentils, corn, cabbage, broccoli, leeks, asparagus, potato, pasta, onions, whole grains, and artificial sweeteners. These foods are rich in sulfur compounds or indigestible fiber, which contribute to the production of gas in the gut.
Excessive flatulence may also be caused by malabsorption syndromes or conditions that result in impairment of digestive processes and infections in the gut. Examples of such conditions include lactose intolerance, malabsorption of fructose, gluten intolerance, Crohn’s disease, biliary and gallbladder diseases, enteritis, pancreatic insufficiency, sorbitol malabsorption, small intestinal bacterial overgrowth, short bowel syndrome, celiac disease, diverticulitis, pseudomembranous colitis, and food poisoning.
Read more on excessive flatulence.
In case of malabsorption or food intolerance, bacterial fermentation of food in the gut increases, leading to increased production of gas. Consumption of carbonated beverages and swallowing air during breathing can also increase the amount of gas in the gut. Conditions that delay the transit of food through the gut also lead to an increase in flatulence. Examples of conditions that cause delayed transit through the intestine include gastroparesis, obstruction of gastric outlet, constipation, diverticulosis, and intestinal obstruction.
Involuntary defecation or expulsion of gas caused by an inability to hold off these events is termed as incontinence. The external anal sphincter is usually under voluntary control, which allows us to hold off expulsion of feces and flatus till we find an appropriate setting. However, damage to the nerves that supply the muscles of the anal sphincters can eliminate this voluntary control, resulting in fecal incontinence and uncontrollable flatulence.
Examples of conditions that can cause incontinence include spinal cord injury, diabetic neuropathy, spina bifida, vaginal delivery, stroke, and degenerative conditions affecting the nervous system. In some cases, incontinence may occur without any accompanying dysfunction of the sphincter. This is termed as functional incontinence. Fecal incontinence is more common in the elderly and wheelchair-bound individuals.
Treatment for Uncontrollable Flatulence
The exact treatment for flatulence depends on the nature of the underlying cause. Taking probiotics, simethicone, activated charcoal, and tricyclic antidepressants may help in various cases of uncontrollable flatulence. However, the benefits of these measures have not been proven conclusively. Avoiding foods that promote excessive gas formation may help in the long term management of uncontrollable flatulence.