Breath tests and irritable bowel syndrome

Abstract

Breath tests are non-invasive tests and can detect H₂ and CH₄ gases which are produced by bacterial fermentation of unabsorbed intestinal carbohydrate and are excreted in the breath. These tests are used in the diagnosis of carbohydrate malabsorption, small intestinal bacterial overgrowth, and for measuring the orocecal transit time. Malabsorption of carbohydrates is a key trigger of irritable bowel syndrome (IBS)-type symptoms such as diarrhea and/or constipation, bloating, excess flatulence, headaches and lack of energy. Abdominal bloating is a common nonspecific symptom which can negatively impact quality of life. It may reflect dietary imbalance, such as excess fiber intake, or may be a manifestation of IBS. However, bloating may also represent small intestinal bacterial overgrowth. Patients with persistent symptoms of abdominal bloating and distension despite dietary interventions should be referred for H₂ breath testing to determine the presence or absence of bacterial overgrowth. If bacterial overgrowth is identified, patients are typically treated with antibiotics. Evaluation of IBS generally includes testing of other disorders that cause similar symptoms. Carbohydrate malabsorption (lactose, fructose, sorbitol) can cause abdominal fullness, bloating, nausea, abdominal pain, flatulence, and diarrhea, which are similar to the symptoms of IBS. However, it is unclear if these digestive disorders contribute to or cause the symptoms of IBS. Research studies show that a proper diagnosis and effective dietary intervention significantly reduces the severity and frequency of gastrointestinal symptoms in IBS. Thus, diagnosis of malabsorption of these carbohydrates in IBS using a breath test is very important to guide the clinician in the proper treatment of IBS patients.

Keywords: Bacterial overgrowth; Breath test; Carbohydrate malabsorption; Irritable bowel syndrome; Lactulose breath test; Small intestine; Sorbitol breath test

Core tip: Bloating and distention are often attributed to dietary factors by patients with irritable bowel syndrome (IBS). Recently, small intestinal bacterial overgrowth (SIBO) has been advocated as a pathogenetic factor of IBS. Sugar malabsorption in the bowel can lead to bloating, cramps, diarrhea and other symptoms of IBS as well as affecting absorption of other nutrients. The breath test is now a well-established noninvasive test for assessing malabsorption of sugars in the small intestine. The glucose breath test has been reported as a better diagnostic method for determination of SIBO. Therefore, this review highlights the role of breath tests in diagnosis and management of IBS.