2006 Volume 37 Issue 2 Pages 99-104
Breath hydrogen (H2) and methane (CH4) measurements are widely used to evaluate carbohydrate malabsorption, bacterial overgrowth and oro-cecal transit time. It was reported that 2-20% of carbohydrates escape small intestinal absorption and reached the colon. Based on this fact, colonic fermentation is considered to be present more frequency than expected. If bacteria exist in the small intestine or unabsorbed carbohydrates reach the cecum, the glucose ingested will be metabolized by gut flora and H2 or CH4 is produced in the intestinal tract. Because bacteria represent the sole source of gut H2 and CH4, fasting breath H2 and CH4 gases have been used as markers of colonic fermentation. Methanogenic bacteria utilize H2, carbon dioxid, and then synthesize CH4. As gastric acid plays an important part in the prevention of bacterial colonization of the stomach and the small intestine, reduction of gastric acid secretion often results in bacterial overgrowth. If the fermentation occurs in the stomach or proximal small intestine, it inhibits gastric and pancreatic secretions, and also influences lower esophageal sphincter function in gastroesophageal reflux disease. Although breath tests such as measuring fasting or postprandial H2 concentrations are noninvasive, avoiding the risk of sampling error, the site of overgrowth cannot be identified. Therefore, we also measured intragastric and intraduodenal H2 and CH4 concentrations to determine the site of fermentation. In the future, the expansion of H2 and CH4 measurement may make it possible that breath testing may be adopted as a primary approach to the diagnosis of digestive diseases which have avoided older invasive methods.
