Intestinal Gas
(Belching, Bloating, Flatulence)
What causes belching?
The ability to belch is almost
universal. Belching, also known as burping, is the act of expelling gas
from the stomach out through the mouth.
The usual cause of belching is a
distended (inflated) stomach caused by swallowed air. The distention of the
stomach causes abdominal discomfort, and the belching expels the air and
relieves the discomfort.
The common reasons for swallowing
large amounts of air (aerophagia) are gulping food or drink too rapidly,
anxiety, and carbonated beverages. People are often unaware that they are
swallowing air.
"Burping" infants during bottle or
breast feeding is important in order to expel air in the stomach that has been
swallowed with the formula or milk.
Excessive air in the stomach is not
the only cause of belching. For some people, belching becomes a habit and does
not reflect the amount of air in their stomachs. For others, belching is a
response to any type of abdominal discomfort and not just to discomfort due to
increased gas.
Everyone knows that when they have
mild abdominal discomfort, belching often relieves the problem. This is because
excessive air in the stomach is often the cause of mild abdominal discomfort. As
a result, people belch whenever mild abdominal discomfort is felt-whatever the
cause.
Belching is not the simple act that
many people think it is. Belching requires the coordination of several
activities. The larynx must be closed-off so that any liquid or food that might
return with the air from the stomach won't get into the lungs.
This is accomplished by voluntarily
raising the larynx as is done when swallowing. Raising the larynx also relaxes
the upper esophageal sphincter so that air can pass more easily from the
esophagus into the throat. The lower esophageal sphincter must open so that air
can pass from the stomach into the esophagus.
While all this is occurring, the
diaphragm descends just as it does when a breath is taken. This increases
abdominal pressure and decreases pressure in the chest. The changes in pressure
promote the flow of air from the stomach in the abdomen to the esophagus in the
chest.
One unusual type of belching has been
described in aerophagic individuals who swallow air. It has been demonstrated
that during some of their belches room air enters the esophagus and is
immediately expelled, giving rise to a belch. This in and out flow of air also
is likely to be the explanation for the ability of many people to belch at will,
even when there is little or no air in the stomach.
If the problem causing the discomfort
is not excessive air in the stomach, then belching does not provide relief. When
belching does not ease the discomfort, the belching should be taken as a sign
that something may be wrong within the abdomen and the cause of the discomfort
should be sought.
Belching by itself, however, does not
help the physician determine what may be wrong because belching can occur in
virtually any abdominal disease or condition that causes discomfort.
What causes bloating?
In discussing bloating, it is
important to distinguish between bloating and distention.
Bloating is the subjective sensation
(feeling) that the abdomen is larger than normal. Thus, bloating is a symptom
akin to the symptom of discomfort.
In contrast, distention is the
objective determination (physical finding) that the abdomen is actually larger
than normal. Distention can be determined by such observations as the inability
to fit into clothes or looking down at the stomach and noting that it is clearly
larger than normal.
In some instances, bloating may
represent a mild form of distention since the abdomen does not become physically
(visibly or measurably) enlarged until its volume increases by one quart.
Nevertheless, bloating should never
be assumed to be the same as distention.
There are three ways in which
abdominal distention can arise. The causes are an increase in air, fluid, or
tissue within the abdomen.
The diseases or conditions that cause
an increase of any of these three factors are very different from one anther.
Therefore, it is important to determine which of them is distending the abdomen.
There are two types of distention;
continuous and intermittent.
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Continuous distention may be caused
by the enlargement of an intra-abdominal (within the abdomen) organ, an
intra-abdominal tumor, a collection of fluid around the intra-abdominal organs
(ascites), or just plain obesity.
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Intermittent distention is usually
due to the occasional accumulation of gas and/or fluid within the stomach,
small intestine, or colon.
What causes flatulence?
Flatulence, also known as farting, is
the act of passing intestinal gas from the anus.
Gas in the gastrointestinal tract has
only two sources. It is either swallowed air or it is produced by bacteria that
normally inhabit the intestines, primarily the colon.
Swallowed air is rarely the cause of
excessive flatulence. The usual source is the production of excessive gas by
intestinal bacteria. The bacteria produce the gas (hydrogen and/or methane) when
they digest foods, primarily sugars and polysaccharides (e.g., starch,
cellulose), that have not been digested during passage through the small
intestine.
Sugars that are commonly poorly
digested (maldigested) and malabsorbed are lactose, sorbitol, and fructose.
Lactose is the sugar in milk. The
absence of the enzyme lactase in the lining of the intestines, which is a
genetic trait, causes the maldigestion. Lactase is important because it breaks
apart the lactose so that it can be absorbed.
Sorbitol is a commonly used sweetener
in low calorie foods. Fructose is a commonly used sweetener in all types of
candies and drinks.
Starches are another common source of
intestinal gas. Starches are polysaccharides that are produced by plants and are
composed of long chains of sugars.
Common sources of different types of
starch include wheat, oats, potatoes, corn, and rice.
Rice is the most easily digested
starch and little undigested rice starch reaches the colon and the colonic
bacteria. Accordingly, the consumption of rice produces little gas.
In contrast, the starches in wheat,
oats, potatoes, and, to a lesser extent, corn, all reach the colon and the
bacteria in substantial amounts. These starches, therefore, result in the
production of appreciable amounts of gas.
The starch in whole grains produces
more gas than the starch in refined (purified) grains. Thus, more gas is formed
after eating foods made with whole wheat flour than with refined wheat flour.
This difference in gas production
probably occurs because the fiber present in the whole grain flour slows the
digestion of starch as it travels through the small intestine. Much of this
fiber is removed during the processing of whole grains into refined flour.
Finally, certain fruits and
vegetables, for example, cabbage, also contain poorly digested starches that
reach the colon and result in the formation of gas.
Most vegetables and fruits contain
cellulose, another type of polysaccharide that is not digested at all as it
passes through the small intestine.
However, unlike sugars and other
starches, cellulose is used only very slowly by colonic bacteria. Therefore, the
production of gas after the consumption of fruits and vegetables usually is not
great unless the fruits and vegetables also contain sugars or polysaccharides
other than cellulose.
Small amounts of air are continuously
being swallowed and bacteria are constantly producing gas.
Contractions of the intestinal
muscles normally propel the gas through the intestines and cause the gas to be
expelled. Flatulence (passing intestinal gas) prevents gas from
accumulating in the intestines.
However, there are two other ways in
which gas can escape the intestine.
First, it can be absorbed across the
lining of the intestine into the blood. The gas then travels in the blood and
ultimately is excreted in the breath.
Second, gas can be removed and used
by certain types of bacteria within the intestine. In fact, most of the gas that
is formed by bacteria in the intestines is removed by other bacteria in the
intestines.
What are the causes of intermittent
abdominal bloating/distention?
Excessive production of gas:
Excessive production of gas by
bacteria is a common cause of intermittent abdominal bloating/distention.
Bacteria can produce too much gas in three ways.
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First, the amount of gas that
bacteria produce varies from individual to individual. In other words, some
individuals may have bacteria that produce more gas, either because there are
more of the bacteria or because their particular bacteria are better at
producing gas.
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Second, there may be poor digestion
and absorption of foods in the small intestine, allowing more undigested food
to reach the bacteria in the colon. The more undigested food the bacteria
have, the more gas they produce. Examples of diseases of that involve poor
digestion and absorption include lactose intolerance, pancreatic
insufficiency, and celiac disease.
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Third, bacterial overgrowth can
occur in the small intestine. Under normal conditions, the bacteria that
produce gas are limited to the colon. In some medical conditions, these
bacteria spread into the small intestine. When this bacterial spread occurs,
food reaches the bacteria before it can be fully digested and absorbed by the
small intestine. Therefore, the bacteria in the small intestine have a lot of
undigested food from which to form gas. This condition in which the
gas-producing bacteria move into the small intestine is called bacterial
overgrowth of the small intestine (bowel).
Excessive production of gas by
bacteria is usually accompanied by more flatulence. Increased flatulence may not
always occur, however, since gas potentially can be eliminated in other
ways-absorption into the body, utilization by other bacteria, or possibly, by
elimination at night without the knowledge of the gas-passer.
Physical obstruction:
An obstruction (blockage) can occur
virtually anywhere from the stomach to the rectum. When the blockage is
temporary or partial, it can cause intermittent abdominal bloating/distention.
For example, scarring of the pylorus
(pyloric stenosis) can obstruct the opening from the stomach into the
intestines, thereby blocking the complete emptying of the stomach.
After meals, the stomach is normally
filled with food and swallowed air. Then, during the next hour or two, the
stomach secretes acid and fluid, which mix with the food and assist in
digestion.
As a result, the stomach distends
further. When the obstruction is incomplete, the food, air, and fluid eventually
pass into the intestines and the bloating/distention resolves.
An obstruction in the small bowel,
which is most commonly due to adhesions from a previous surgery, is another
cause of intermittent abdominal distention.
To make matters worse, the distention
that is caused by the physical obstruction stimulates both the stomach and
intestines to secrete fluid, which adds to the distention.
Finally, severe constipation or fecal
impaction (hardened stool in the rectum) can also obstruct the flow of the
intestinal contents and result in distention.
In this case, however, the
bloating/distention is usually constant and progressive and is relieved by bowel
movements or removal of the impacted stool.
Functional obstruction:
A functional obstruction is not
caused by an actual physical blockage, but rather by the poor functioning of the
muscles of the stomach or intestines that propel the intestinal contents.
When these muscles are not working
normally, the intestinal contents will accumulate and distend the abdomen.
Examples of functional obstruction
include:
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gastroparesis (paralysis of the
stomach) of diabetes;
-
chronic intestinal
pseudo-obstruction, an unusual condition in which the muscles of the small
intestine do not work normally; and
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Hirschprung's disease, in which a
small stretch of colonic muscle does not contract normally due to missing
nerves.
There is accumulating scientific
evidence that some patients with abdominal bloating and distention due to gas
may have a functional abnormality of the intestinal muscles that prevents gas
from being normally transported through the intestine and expelled.
Instead, their gas accumulates in the
intestine. Among patients with irritable bowel syndrome(IBS) with bloating as an
important symptom, the gas accumulates in the small intestine and not the colon.
The gas accumulates during the day and is greatest in the evening.
Fats in food have an effect on the
intestine that mimics a functional obstruction. Dietary fat reaching the small
intestine causes transport of digesting food, gas, and liquid within the
intestines to slow. This can promote the accumulation of food, gas, and liquid
and lead to bloating and/or distention.
Intestinal hypersensitivity:
Some people appear to be very
sensitive (hypersensitive) to distention of their intestines, and they may feel
bloated even with normal amounts of digesting food, gas, and fluid in the
intestine after a meal. The bloating may be aggravated or even progress to
distention if the meal contains substantial amounts of fat.
How are belching,
bloating/distention, and flatulence evaluated?
A patient's medical history is
important because it directs the evaluation. If the bloating/distention is
continuous rather than intermittent, then enlargement of abdominal organs,
abdominal fluid, tumors, or obesity are probable causes.
If the bloating/distention is
associated with increased flatulence, then bacteria and excessive gas production
are likely factors. If a diet history reveals the
consumption of large amounts of milk or dairy products (lactose), sorbitol
or fructose, then the maldigestion and malabsorption of these sugars may be the
cause of the distention.
When individuals complain of
flatulence, it may be useful for them to count the number of times they pass gas
for several days. This count can confirm the presence of excessive flatulence
since the number of times gas is passed correlates well with the total amount
(volume) of passed gas.
As you might imagine, it is not easy
to measure the amount of passed gas. It is normal to pass gas up to 20 times a
day. (The average volume of gas passed daily is estimated to be about ¾ of a
quart.)
If an individual complains of
excessive gas but passes gas fewer than 20 times per day, the problem is likely
to be something other than too much gas.
For example, the problem may be the
foul odor of the gas (usually due to sulfur-containing foods), the lack of
ability to control (hold back) the passing of gas, or the soiling of underwear
with small amounts of stool when passing gas.
All of these problems, like excessive
gas, are socially embarrassing and may prompt individuals to consult a
physician. These problems, however, are not due to excessive gas production, and
their treatment is different.
Simple abdominal X-rays: Simple
X-rays of the abdomen, particularly if they are taken during an episode of
bloating or distention, can often confirm air as the cause of the distention
since large amounts of air can be seen easily within the stomach and intestine.
Moreover, the cause of the problem
may be suggested by noting where the gas has accumulated. For example, if the
air is in the stomach, emptying of the stomach is likely to be the problem.
Small intestinal X-rays: X-rays of
the small intestine, in which barium is used to fill and outline the small
intestine, are particularly useful for determining if there is an obstruction of
the small intestine.
Gastric emptying studies: These
studies measure the ability of the stomach to empty its contents.
For gastric emptying studies, a test
meal that is labeled with a radioactive substance is eaten and a Geiger
counter-like device is placed over the abdomen to measure how rapidly the test
meal empties from the stomach. A delay in emptying of the radioactivity from the
stomach can be caused by any condition that reduces emptying of the stomach
(e.g., pyloric stenosis, gastroparesis).
Ultrasound, CT scan, and MRI: Imaging
studies, including ultrasound examination, computerized tomography (CT), and
magnetic resonance imaging (MRI), are particularly useful in defining the cause
of distention that is due to enlargement of the abdominal organs, abdominal
fluid, and tumor.
Maldigestion and malabsorption tests:
Two types of tests are used to diagnose maldigestion and malabsorption; general
tests and specific tests. The best general test is a 72 hour collection of stool
that measures fat in the stool. If maldigestion and/or malabsorption exist
because of pancreatic insufficiency or diseases of the lining of the small
intestine (e.g., celiac disease), the amount of fat in the stool will increase.
Specific tests can be done for
maldigestion of individual sugars that are commonly maldigested, including
lactose (the sugar in milk) and sorbitol (a sweetener in low calorie foods).
The specific tests require ingestion
of the sugars followed by hydrogen/methane breath testing.
The sugar fructose, a commonly used
sweetener, like lactose and sorbitol, also may cause abdominal
bloating/distention and flatulence.
However, the problem that can occur
with fructose is different from that with lactose or sorbitol. Thus, as already
discussed, lactose and sorbitol may be poorly digested by the pancreas and small
intestine.
On the other hand, fructose may be
digested normally but may pass so rapidly through the small intestine that there
is not enough time for digestion and absorption to take place.
Hydrogen/methane breath tests: The
most convenient way to test for bacterial overgrowth of the small intestine is
hydrogen/methane breath testing. Normally, the gas produced by the
bacteria of the colon is composed of hydrogen and/or methane.
For hydrogen/methane breath testing,
a non-digestible sugar, lactulose, is consumed. At regular intervals following
ingestion, samples of breath are taken for analysis.
When the lactulose reaches the colon,
the bacteria form hydrogen and/or methane. Some of the hydrogen or methane is
absorbed into the blood and eliminated in the breath where it can be measured in
the samples of breath.
In normal individuals, there is one
peak of hydrogen or methane when the lactulose enters the colon.
In individuals who have bacterial
overgrowth, there are two peaks of hydrogen or methane. The first occurs when
the lactulose passes and is exposed to the bacteria in the small intestine. The
second occurs when the lactulose enters the colon and is exposed to the colonic
bacteria.
Hydrogen breath testing for
overgrowth also may be done utilizing glucose as the test sugar.
How is excessive intestinal gas
treated?
The treatment of excessive intestinal
gas depends on the cause. If there is maldigestion of specific sugars-lactose,
sorbitol, or fructose--the offending sugars can be eliminated from the diet. In
the case of
lactose
in milk, an alternative treatment is available. Enzymes that are similar to
intestinal lactase can be added to the milk in order to break down the lactose
prior to its ingestion so that it can be absorbed normally
Some people find that yogurt, in
which the lactose has been broken down partially by bacteria, produces less gas
than milk.
There also are certain types of
vegetables and fruits that contain types of starches that are poorly digested by
people but well digested by bacteria.
These include beans, lentils,
cabbage, brussel sprouts, onions, carrots, bananas, apricots, and prunes.
Reducing the intake of these
vegetables and fruits, as well as foods made from whole grains, should reduce
gas and flatulence. However, the list of gas-producing foods is rather long, and
it may be difficult to eliminate them all without severely restricting the diet.
When maldigestion is due to
pancreatic insufficiency, then supplemental pancreatic enzymes can be ingested
with meals to replace the missing enzymes.
If maldigestion and/or malabsorption
is caused by disease of the intestinal lining, the specific disease must be
identified, most commonly through a small bowel biopsy. Then, treatment can be
targeted for that condition.
For example, if celiac disease is
found on the biopsy, a gluten-free diet can be started.
An interesting form of treatment for
excessive gas is alpha-D-galactosidase, an enzyme that is produced by a mold.
This enzyme, commercially available as Beano, is consumed as either a liquid or
tablet with meals.
This enzyme is able to break down
some of the difficult-to-digest polysaccharides in vegetables so that they may
be absorbed. This prevents them from reaching the colonic bacteria and causing
unnecessary production of gas. Beano has been shown to be effective in
decreasing the incidence of intestinal gas.
Two other types of treatment have
been promoted for the treatment of gas;
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simethicone and
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activated charcoal.
It is unclear if simethicone has an
effect on gas in the stomach. However, it has no effect on the formation of gas
in the colon.
Moreover, in the stomach, simethicone
would be expected only to affect swallowed air, which, as previously mentioned,
is an uncommon cause of excessive intestinal gas.
Nevertheless, some individuals are
convinced that simethicone helps them. Activated charcoal has been shown to
reduce the formation of gas in the colon, though the way in which it does so is
unknown.
If there is a physical obstruction to
the emptying of the stomach or passage of food, liquid, and gas through the
small intestine, then surgical correction of the obstruction is required.
If the obstruction is
functional,
medications that promote activity of the muscles of the stomach and small
intestine are given. Examples of these medicines are erythromycin or
metoclopramide (Reglan).
Bacterial overgrowth of the small
bowel is usually treated with antibiotics. However, this treatment is frequently
only temporarily effective or not effective at all.
When antibiotics provide only a
temporary benefit, it may be necessary to treat patients intermittently or even
continuously with antibiotics. If antibiotics are not effective, probiotics
(e.g., lactobacillus) can be tried although their use in bacterial overgrowth
has not been studied. This condition may be difficult to treat.
Intestinal Gas At a Glance
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The usual cause of belching is
excessive gas in the stomach that comes from swallowed air. However,
discomfort in the abdomen for any reason may also cause belching. Therefore,
belching does not always indicate the presence of excessive gas in the
stomach.
-
Bloating is the subjective feeling
that the abdomen is enlarged but does not necessarily mean that the abdomen
is, in fact, enlarged. Distention is the objective enlargement of the abdomen.
-
Continuous distention of the
abdomen is usually caused by fluid, tumors, enlarged organs, or fat within the
abdomen.
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Intermittent distention of the
abdomen may be caused by excessive formation of intestinal gas, as well as
physical or functional obstruction of the intestines.
Flatulence results from the production of gas by bacteria within the
intestines when they digest sugars and polysaccharides.
-
Excessive production of gas and
increased flatulence may occur because of:
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the greater ability of some
bacteria to produce gas;
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maldigestion or malabsorption of
sugars and polysaccharides; and
-
bacterial overgrowth of the small
intestine.
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Belching, bloating/distention, and
flatulence are evaluated with a medical history, simple abdominal X-rays,
small intestinal X-rays, gastric emptying studies, ultrasound examination,
computerized tomography (CT), magnetic resonance imaging (MRI), tests for
maldigestion and malabsorption, and hydrogen breath testing.
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The treatment of excessive
intestinal gas depends on the underlying cause and may include dietary
changes, medications that reduce the amount of gas, medications that stimulate
the muscles of the intestine, or antibiotics.
The above opinionated views and information serves to educated
and informed consumer .
The information provided herein
should not be used during any medical emergency or for the diagnosis or
treatment of any medical condition. .It
should not replaced professional advise and consultation.
A licensed physician should be consulted for diagnosis and treatment of any and
all medical conditions
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