breath tests, diagnostic tests for intestinal disorders such as bacterial overgrowth, ileal disease, lactase deficiency, and steatorrhea. Lactose malabsorption is treated by giving the patient 12.5 to 25.0 grams of lactose and measuring the amount of hydrogen excreted in the breath. If lactose absorption is impaired in the small intestine, colonic bacteria ferment the lactose, releasing hydrogen, which is excreted in the breath. Bacterial overgrowth is tested with 14C-cholylglycine, which is normally absorbed by the ileum and recycled via the enterohepatic circulation. In cases of bacterial overgrowth the labeled glycine is removed by conjugation in the small intestine, absorbed, and metabolized, resulting in an increase of 14CO2 in the breath. Breath tests are also used to test for the presence of Helicobacter pylori.
