Hydrogen Breath Test (cont.)
When is hydrogen breath testing used?
Hydrogen breath testing is used in the
diagnosis of three conditions.
- The first is a condition in which dietary sugars are not digested
normally. The most common sugar that is poorly digested is
lactose, the sugar in
milk. Individuals who are unable to properly digest lactose are referred to
as lactose intolerant.
Testing also may be used to diagnose problems with the digestion of other
sugars such as sucrose,
fructose and sorbitol.
- The second condition for which hydrogen breath testing is used is for
diagnosing bacterial overgrowth of the small bowel, a condition in which
larger-than-normal numbers of colonic bacteria are present in the small
intestine.
- The third condition for which hydrogen breath testing is used is for
diagnosing rapid passage of food through the small intestine. All three of
these conditions may cause
abdominal pain, abdominal
bloating and distention,
flatulence (passing gas in large amounts), and
diarrhea.
How does hydrogen breath testing work?
The bacteria in the colon, including the anaerobic bacteria, are able
to digest and use sugars and carbohydrates as food. When the anaerobic bacteria
digest sugars and carbohydrates, they convert some of the sugars and
carbohydrates into gases, most commonly hydrogen. They also may produce and
release into the colon other substances, for example, chemicals that cause the
colon to secrete water and cause diarrhea.
As previously discussed, some of the hydrogen gas is absorbed by the colon
into the blood and is eliminated in the breath where it can be measured. As long
as little sugar or carbohydrate
reaches the colon, the small amounts of gas and other substances that are
produced do not cause a problem. When larger amounts of sugar or carbohydrate
reach the colon because they are not digested and absorbed in the small
intestine, larger amounts of gas and substances are formed in the colon.
For example, if an individual digests and absorbs the sugar in milk (lactose)
normally, then none of the lactose that is given for the lactose hydrogen breath
test reaches the colon, and no increase in the concentration of hydrogen in the
breath is seen during the breath test. On the other hand, if the individual does
not digest and
absorb the lactose
completely, that is, he or she is lactose intolerant, the lactose travels
through the small intestine and enters the colon where the bacteria digest it
and produce hydrogen. An increase in hydrogen in the breath then is seen. Other
sugars for which poor digestion can be diagnosed by breath testing include
sucrose and fructose (found in corn syrup), and sorbitol (a sugar that is used
as a low-calorie sweetener).
There are ways other than
abnormal digestion of dietary sugars by which the bacteria can cause
problems. Unlike in the colon, the number of hydrogen-producing, anaerobic
bacteria in the small intestine is small. If, however, large numbers of
hydrogen-producing bacteria move into the small intestine from the colon, a
condition called bacterial overgrowth of the small bowel, the bacteria may
digest the sugars and carbohydrates before the small bowel has had a chance to
digest and absorb them and produce large amounts of hydrogen.
Finally, if individuals have abnormally rapid passage of food through the
small intestine, there may not be enough time for the small intestine to digest
and absorb sugars and carbohydrates. This results in the entry of larger amounts
of sugar and carbohydrate into the colon where the bacteria can digest and
convert them to gas.
To diagnose bacterial overgrowth and rapid transit through the small
intestine, a sugar that is not digested and absorbed by man, such as lactulose,
usually is used for the test. In the case of rapid passage through the small
intestine, the sugar passes quickly through the small intestine and into the
colon so that hydrogen is found in the breath very soon after ingestion of the
sugar. In the case of bacterial overgrowth, production of hydrogen occurs twice
during the test. Once as the sugar passes the bacteria in the small intestine
and again when the sugar enters the colon.
Next: How is hydrogen breath testing performed? »
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