Controversies in Small Intestinal Bacterial Overgrowth

Educational Objectives

The goal of this program is to improve the diagnosis and treatment of small intestinal bacterial overgrowth (SIBO). After hearing and assimilating this program, the clinician will be better able to:

1. Interpret the findings of breath testing in patients with suspected small intestinal bacterial overgrowth (SIBO).

2. Select patients with small intestinal bacterial overgrowth (SIBO) who are most likely to benefit from a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) and from promotility agents.

Summary

Background: small intestinal bacterial overgrowth (SIBO) refers to excessive amounts of bacteria in small intestine; symptoms include bloating, flatulence, diarrhea, constipation, dyspepsia, nausea, and fatigue; severe SIBO associated with symptoms of malabsorption; incidence of SIBO in patients with irritable bowel syndrome (IBS) 4% to 78%; do not empirically treat nonspecific symptoms; diagnose SIBO with breath testing or small bowel aspiration and culture

Breath testing: inexpensive, noninvasive, and widely available; human cells incapable of producing methane or hydrogen; bacteria produce hydrogen or methane in response to substrate (lactulose or glucose); changes in concentrations of hydrogen or methane from baseline indicate SIBO; hydrogen- and methane-predominant types of SIBO most prevalent; both types associated with abdominal distention and bloating; methane-predominant SIBO associated with constipation

Diagnosis of SIBO: determined by increase in hydrogen concentration ≥20 ppm from baseline in 90 min or methane concentration ≥10 ppm ; interpretation unclear if baseline for hydrogen concentration already high or diet not followed before testing; hydrogen sulfide SIBO — emerging as new diagnosis; hydrogen sulfide–producing bacteria compete with methane-producing bacteria for consumption of hydrogen; traditional breath test indicates little to no hydrogen or methane (flat line); test for hydrogen sulfide SIBO lacking; patients present with more diarrhea and abdominal pain; analyze findings of breath tests carefully to avoid overlooking patients with hydrogen sulfide SIBO who have negative breath tests

Role of diet: patients with SIBO have carbohydrate intolerance (to, eg, lactose, fructose, fructan); order SIBO breath test before other carbohydrate testing

Diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs): significantly affects gut microbiota and improves symptoms of IBS; majority of studies in patients with IBS (not SIBO); diet low in fermentable foods decreases chance for bacterial overgrowth by creating less favorable luminal environment for bacteria; low-FODMAP diet developed to treat symptoms of IBS; in 75% of patients with IBS who follow diet low in FODMAPs, symptoms improve; refer patient to nutritionist (if possible); FODMAPs short-chain carbohydrates characterized by limited absorption in small intestine, intense bacterial fermentation, and high osmotic activity; in intestines of patients with IBS, dietary FODMAPs induce production of hydrogen and methane; effect of diet low in FODMAPs — reduction in global symptoms; greater reductions in average daily scores for abdominal pain, bloating, consistency, frequency, and urgency compared with modified National Institute for Health and Care Excellence guideline diet; phases of diet low in FODMAPs — start with strict adherence to diet for 2 to 6 wk; over next 8 to 12 wk, add one FODMAPs food back to diet; if patient asymptomatic with first food after 3 days, introduce next food; avoid foods causing symptoms; develop individualized low-FODMAPs diet for each patient; avoid long-term use of diet

Treatment: activation of migrating motor complex (MMC) key; MMC cyclic recurring motility pattern in stomach and small intestine during fasting (interrupted by feeding); phase 3 of MMC most active and inducible; encourage patients to maintain 4-hr gaps between meals and avoid eating before bedtime; encourage 12-hr fast overnight to engage more MMC activity

Promotility agents: prucalopride — selective serotonin 5-HT4 receptor agonist; stimulates colonic peristalsis; approved by US Food and Drug Administration for idiopathic constipation; release of acetylcholine enhances amplitude of contractions to stimulate peristalsis; studies suggest prucalopride improves gastric and small bowel transit times; contraindications include hypersensitivity reactions, severe inflammatory bowel disease, and obstruction; adverse reactions include headache, abdominal pain, nausea, and diarrhea; suicide, suicide attempts, and suicidal ideation reported (causality not established); discontinue therapy in patients with worsening depression or suicidal thoughts; safe in geriatric patients; decrease dose in patients with creatinine clearance <30 mL/min; erythromycin — motilin receptor agonist; stimulates enteric nerves in smooth muscle and triggers MMC; low doses (50 mg/day) not associated with antibiotic properties; tegaserod (Zelnorm) — inhibits visceral sensitivity, enhances vasomotor activity, normalizes impaired motility throughout gastrointestinal tract, and starts phase 3 of MMC; voluntarily withdrawn from market in 2002 because of possible increase in risk for myocardial infarction, stroke, and unstable angina; available now for women aged <65 yr with IBS and constipation and no history of ischemic cardiovascular disease

Readings

Banik GD et al: Hydrogen sulphide in exhaled breath: A potential biomarker for small intestinal bacterial overgrowth in IBS. J Breath Res, 2016 May;10(2):026010; Hill P et al: Controversies and recent developments of the low-FODMAP diet. Gastroenterol Hepatol (N Y), 2017 Jan;13(1):36–45; Quigley EM: Prucalopride: safety, efficacy and potential applications. Therap Adv Gastroenterol, 2012 Jan;5(1):23–30; Rezaie A et al: How to test and treat small intestinal bacterial overgrowth: An evidence-based approach. Curr Gastroenterol Rep, 2016 Feb;18(2):8.

Disclosures

 For this program, members of the faculty and planning committee reported nothing to disclose. In her lecture, Dr. Veloso presents information related to the off-label or investigational use of a therapy, product, or device.

Acknowledgements

Dr. Veloso was recorded at the 45th Annual Topics in Gastroenterology and Hepato-Biliary Update, held October 2-4, 2019, in Baltimore, MD, and presented by Johns Hopkins University School of Medicine. For more information about upcoming CME activities sponsored by Johns Hopkins University School of Medicine, please visit hopkinsCME.cloud-cme.com. The Audio Digest Foundation thanks the speakers and sponsors for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

GE340802

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.