Comparative Assessment of Radioisotope Glucose and Breath Test

Small Intestinal Bacterial Overgrowth

This is a research study about improving our diagnostic method for small intestinal bacterial overgrowth (SIBO). Patients undergoing Standard of Care (SOC) Endoscopically assisted glucose breath test (EAGBT) will undergo upper endoscopy and glucose breath tests. In this study, investigators wish to utilize Nuclear Medicine techniques to locate where the glucose solution that is administered during EAGBT is being consumed by bacteria is in the small bowel when it detects SIBO.

Small intestinal bacterial overgrowth (SIBO) is characterized by bloating, gas, distention, and diarrhea due to colonization and an excessive amount of bacteria in the small bowel. Distal SIBO is the presence of excessive amounts of bacteria in the distal jejunum and/or ileum. Diagnosis of SIBO requires either duodenal aspirate with culture analysis or more commonly with breath hydrogen/methane testing. Hydrogen breath testing often uses either oral glucose or lactulose solutions. If bacteria are present in the small bowel they will ferment glucose or lactulose, producing hydrogen or methane as a byproduct. These gases are absorbed into the bowel, and then eliminated via pulmonary expiration. By detecting a rise in breath H2 and CH4 values compared to baseline, SIBO can be diagnosed. However, after oral ingestion, the majority of the glucose substrate is absorbed in the duodenum and proximal jejunum. Therefore, Glucose breath test (GBT) is good for the detection of proximal SIBO, but misses distal SIBO. Investigators have recently shown that glucose administration into the distal duodenum through upper endoscopy has a higher positive yield for SIBO in patients with negative oral GBT. However, it is unclear if the rise in breath H2 or CH4 is because of glucose fermentation by bacteria in the distal small bowel or from fermentation by bacteria in the colon, i.e. false-positive test. Study objective here is to administer a radio-labeled glucose solution into the duodenum via an endoscopically placed nasoduodenal tube, and then determine if the rise in breath hydrogen and/or methane correlates with the location of the isotopic glucose solution in the bowel by simultaneous nuclear imaging. Results of breath testing will also be compared with duodenal aspirate/cultures taken at the time of endoscopy. Clinical response to treatment will be assessed on follow up.

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