Hydrogen & Methane Breath Testing
Hydrogen and methane breath testing are used to diagnose lactose and fructose intolerance and small bowel bacterial overgrowth. These disorders can result in problems with gas, bloating, diarrhea, and abdominal cramping. Patients with these problems are often misdiagnosed as having irritable bowel syndrome.
Lactose is the main sugar in milk. Normally, lactose is digested in the small intestine and absorbed into the blood stream. If adequate absorption occurs, no lactose leaves the small intestine and enters the colon. However, if a patient has lactose intolerance, their small bowel cannot digest the lactose and it enters the colon. In the colon it is consumed by colonic bacteria which release hydrogen and methane gas as a by product of digestion. The hydrogen and methane gases rapidly diffuse across the colonic mucosa into the bloodstream and then can be measured in the breath.
Fructose is a sugar that is used to sweeten many foods including soft drinks. Fructose is also naturally found in many juices such as orange juice. It is also known as corn syrup. As with lactose, many people cannot adequately absorb fructose from the small intestine. It passes into the colon where it is digested by bacteria and hydrogen and methane gases are released causing symptoms such as bloating, gas, abdominal distention, and diarrhea.
Normally, the colon contains a very high level of bacteria while the small intestine has virtually no bacteria and is essentially sterile. In some people, bacteria will leave the colon and begin to live in the small bowel. This can alter the normal bowel function and result in diarrhea, cramping, gas and other problems. It can be diagnosed by doing a breath test using a special sugar called lactulose.
For the breath tests, a baseline breath sample is obtained by having the patient blow into a machine. Patients will then be asked to drink lactose, fructose, or lactulose- depending on the specific test ordered. Breath samples are recorded at 15 minute intervals for two hours. A positive test occurs when there is noted to be a significant rise in the breath hydrogen or methane level.
This is generally felt to be a safe test with minimal if any complications.