Intestinal Gas (Belching, Bloating, Flatulence) (cont.)
How are belching, bloating/distention, and flatulence evaluated?
Medical history
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 (often due to
ingestion of 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 (for example, 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 for example, 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. (See below.) 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 described, lactose and sorbitol may be poorly digested by the pancreatic
enzymes
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 lactose, glucose,
sorbitol, or fructose as the test
sugar.
Next: How is excessive intestinal gas treated? »
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