Hydrogen breath testing

Why do patients need this test?
Many people absorb food sugars poorly allowing them to pass into the colon where fermentation of incompletely absorbed sugars can result in symptoms such as bloating, abdominal pain, excessive wind, and disturbances of bowel habit. This can be particularly the case with lactose found in milk and milk products, and fructose found in many fruits. Malabsorption of lactose and fructose (as well as otherfermentable oligo- di- and monosaccharides and polyhydric alcohols, so called FODMAPS) is recognised increasingly as a contributor to symptoms in irritable bowel syndrome.

Small intestinal bacterial overgrowth (SIBO) is a condition in which abnormal colonisation of the small intestine with colonic bacteria takes place. A small but significant proportion of patients previously diagnosed with IBS can be identified to have SIBO.

What will the test detect?
Both carbohydrate malabsorption and small intestinal bacterial overgrowth can be detected by hydrogen breath testing. The tests are non-invasive and are performed in an outpatient setting. The test is based on the principle that as human cells do not produce hydrogen, most hydrogen exhaled in the breath originates as a product of bacterial fermentation in the gut. In a patient with lactose or fructose malabsorption given an oral sugar load, a rise in breath hydrogen is seen which corresponds to the arrival of unabsorbed sugar in the colon. In SIBO patients given an oral glucose load an early rise in breath hydrogen is seen which corresponds to the action of bacterial metabolism of glucose in the small intestine. 

How is the test carried out?
Patients undergoing hydrogen breath testing attend fasting, having avoided complex carbohydrates in their previous meal and without having received recent antibiotic or laxative therapy. An initial breath sample is taken, followed by ingestion of the sugar substrate, after which timed collections of breath samples are taken for up to 2 hours. Breath samples are analysed immediately in the outpatient department using a breath hydrogen analyser. The results from their tests will then be reported by Dr Ken Trimble, Consultant Gastroenterologist.

How do I refer a patient?
Patients are required to be referred to a Gastroenterologist in the first instance, via SCI gateway or fax, the Gastroenterologist can then recommend the testing if necessary. 

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