Irritable bowel syndrome – controversies in diagnosis and management

ABSTRACT

Introduction

The irritable bowel syndrome (IBS) is the best-recognized disorder of gut brain interactions (DGBI). However, it is controversial if the Rome IV criteria iteration for IBS diagnosis is fit for purpose.

Areas covered

This review critically evaluates Rome IV criteria for diagnosis of IBS and addresses clinical considerations in IBS treatment and management, including dietary factors, biomarkers, disease mimics, symptom severity, and subtypes. The role of diet in IBS is critically reviewed along with the influence of the microbiota, including small intestinal bacterial overgrowth.

Expert opinion

Emerging data suggest the Rome IV criteria are more suitable for identifying severe IBS and least useful for sub-diagnostic patients who are still likely to benefit from IBS treatment. Despite convincing evidence that IBS symptoms are diet-driven and often postprandial, a relationship to eating is not a Rome IV diagnostic criterion. Few IBS biomarkers have been identified, suggesting the syndrome is too heterogeneous to be measured by a single marker, and combined biomarker, clinical, dietary, and microbial profiling may be needed for objective characterization. With many organic diseases mimicking and overlapping with IBS, it’s important clinicians are knowledgable about this to mitigate the risk of missing comorbid organic intestinal disease and to optimally treat IBS symptoms.

KEYWORDS:

• Irritable bowel syndrome
• DGBI
• SIBO
• gut microbiota
• FODMAP diet

Article highlights

• The change to IBS diagnostic criteria from abdominal ‘discomfort’ to ‘pain’ has had substantial implications, especially to research studies, with a likely ‘knock on’ effect for clinical practice.

• Treating people with gut–brain disorders based only on a single gastrointestinal diagnosis is fraught because overlap between IBS and other conditions is common. ‘Labelling’ can result in residual complaints being ignored or debilitating IBS being overlooked if a comorbid condition is deemed more important.

• When considered alongside clinical history and diagnostic criteria, a low FODMAP diet has a high sensitivity for IBS. Used judiciously, a ‘diet first’ approach may be helpful in differentiating IBS from IBS mimics, including organic gastrointestinal disease, reassuring clinicians.

• Important areas of investigation in IBS include more nuanced and personalized dietary therapy, gut-brain axis therapies, and altering the microbiota.

Declaration of interest

K Duncanson is a company director for the Good Gut Group, that has patented functional bread and grain product concepts (Australian Patent No. 2014262285; New Zealand Patent No.629207) for Irritable Bowel Syndrome (IBS) consumers. Good Gut Group had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish. NJ Talley reports: non-financial support from Norgine (2021) (IBS interest group); personal fees from Allakos (gastric eosinophilic disease) (2021), Bayer (IBS) (2020), Planet Innovation (Gas capsule IBS) (2020), twoXAR Viscera Labs (U.S.A 2021) (IBS-diarrhea), Dr Falk Pharma (2020) (EoE), Sanofi-aventis, Glutagen (2020) (celiac disease), IsoThrive (2021) (esophageal microbiome), BluMaiden (microbiome advisory board) (2021), Rose Pharma (IBS) (2021), Intrinsic Medicine (2022) (human milk oligosaccharide), Comvita Mānuka Honey (2021) (digestive health), Astra Zeneca (2022), outside the submitted work; a patent Nepean Dyspepsia Index (NDI) 1998, Biomarkers of IBS licensed, a patent Licensing Questionnaires Talley Bowel Disease Questionnaire licensed to Mayo/Talley, a patent Nestec European Patent licensed, a Singapore Provisional Patent ‘Microbiota Modulation of BDNF Tissue Repair Pathway’ issued, ‘Diagnostic marker for functional gastrointestinal disorders’ Australian Provisional Patent Application 2021901692; participation in committees: OzSage, NHMRC Council member, Asia Pacific Association of Medical Journal Editors, Rome V Working Team Member (Gastroduodenal Committee), International Plausibility Project Co-Chair (Rome Foundation funded), COVID−19 vaccine forum member (by invitation only); advisory board roles for IFFGD (International Foundation for Functional GI Disorders), AusEE; editorial roles for Medical Journal of Australia (Editor in Chief), Mayo Clinic Proceedings (Assoc Ed), Up to Date (Section Editor), Precision and Future Medicine, Sungkyunkwan University School of Medicine, South Korea, Med (Journal of Cell Press); funding support from the National Health and Medical Research Council (NHMRC) to the Centre for Research Excellence in Digestive Health and holds an NHMRC Investigator grant. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.