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Guidelines

TL;DR — Six or more societies have issued IBS guidance since 2015 and they agree on the frame and disagree on the details. Universal agreement: make a positive diagnosis rather than a diagnosis of exclusion, investigate sparingly, and exclude coeliac disease. Near-universal agreement: a limited trial of low-FODMAP diet, gut–brain neuromodulators for persistent symptoms, and gut-directed psychological therapy. The disagreements are substantive and can be named precisely. SSRIs: AGA makes a conditional recommendation against them in both IBS-C and IBS-D (Chang 2022, PMID 35738724; Lembo 2022, PMID 35738725) while the 2025 meta-analysis they would now be judged on finds them modestly effective for abdominal pain (RR 0.74, 0.56–0.99; Khasawneh 2025, PMID 40258375). Bile acid testing: BSG-aligned guidance recommends SeHCAT in IBS-D because roughly a third have bile acid diarrhoea (Black 2020, PMID 32133113), while ACG does not make it routine. Breath testing for SIBO: ACG has a dedicated SIBO guideline that codifies testing (Pimentel 2020, PMID 32023228), while BSG-aligned guidance states there is "no role for routine hydrogen breath tests" in suspected IBS (Black 2020, PMID 32133113). Overlap: only the Asia-Pacific working group provides algorithms for IBS overlapping functional dyspepsia (Gwee 2023, PMID 36321167). And the strength of recommendation is asymmetric by subtype: AGA's IBS-C guideline contains one strong recommendation (linaclotide, high certainty) and its IBS-D guideline contains none at all.

The documents

Body Year Region Scope Citation
ACG 2021 USA Full management guideline; 25 questions (9 diagnostic, 16 therapeutic), GRADE + modified Delphi Lacy 2021, PMID 33315591
BSG 2021 UK Full management guideline; updated trial-based and network meta-analyses commissioned for it, GRADE Vasant 2021, PMID 33903147
AGA (IBS-C) 2022 USA Pharmacological management of IBS-C only; 9 recommendations, GRADE Chang 2022, PMID 35738724
AGA (IBS-D) 2022 USA Pharmacological management of IBS-D only; 8 recommendations, GRADE Lembo 2022, PMID 35738725
NICE CG61 2008; recommendations updated 2017; surveillance review 2025 UK Diagnosis and management in primary care NICE — "Irritable bowel syndrome in adults: diagnosis and management", https://www.nice.org.uk/guidance/cg61, accessed 2026-09-02
JSGE 2020 (2nd ed; 1st ed 2015) Japan 41 questions; three-step therapeutic algorithm Fukudo 2021, PMID 33538894; 1st ed Fukudo 2015, PMID 25500976
Korean (Seoul Consensus) 2025 (revising 2017) Korea 22 recommendations, de novo + adaptation, modified Delphi Choi 2025, PMID 40205893; 2017 edition Song 2018, PMID 29605976
Italian joint consensus 2023 Italy Seven societies including paediatrics Barbara 2023, PMID 36517261
UEG/ESNM 2022 Europe Functional bowel disorders with diarrhoea Savarino 2022, PMID 35695704
APAGE 2023 Asia-Pacific Functional dyspepsia overlapping other GI symptoms, incl. IBS Gwee 2023, PMID 36321167
Asian Consensus (2nd) 2019 Asia Regional consensus Gwee 2019, PMID 31327218
AMG position statement 2024/2025 Mexico Pharmacological treatment only, 14 experts Remes-Troche 2025, PMID 40307155
WGO 2015 (published 2016) Global Global perspective with resource-tiered cascades Quigley 2016, PMID 27623513
German S3 (DGVS / DGNM) 2021 (superseding 2011) Germany Updated definition, pathophysiology, diagnosis and treatment; DGVS lists revision in progress Layer 2021, PMID 34891206
CAG 2019 Canada IBS management, GRADE consensus; historical catalogue omission corrected Moayyedi 2019, PMID 31294724
Argentine expert consensus 2026 Argentina Adjacent: breath testing and microbial-overgrowth management in DGBI; abstract-level catalogue entry Soifer 2026, PMID 42816255
BDA (dietetic) 2016 update UK Dietary management; companion probiotics review McKenzie 2016, PMID 27272325; PMID 27265510
ACG (SIBO) 2020 USA Adjacent: SIBO diagnosis and treatment Pimentel 2020, PMID 32023228
ESPGHAN/NASPGHAN 2025 Europe/N America Paediatric IBS and functional abdominal pain, ages 4–18 Groen 2025, PMID 40444524
Italian paediatric 2024 Italy Children and adolescents Di Nardo 2024, PMID 38486305
NICE chronic primary pain 2021 UK Adjacent: applies to chronic primary pain generally and is used alongside condition-specific guidance NICE — "Chronic pain (primary and secondary) in over 16s", https://www.nice.org.uk/guidance/ng193, accessed 2026-09-02

The German and Canadian entries correct omissions discovered on 2026-10-14; they are older publications, not new guidance from this sweep window. DGVS still labels the posted guideline June 2021 and says it is being revised (DGVS — “Reizdarmsyndrom”, https://www.dgvs.de/leitlinien/unterer-gi-trakt/reizdarmsyndrom/, accessed 2026-10-14). The Argentine full text was inaccessible, so its recommendations and grades have not been added to the comparison below.

A structured catalogue with status and supersession chains is in literature/guidelines/REGISTRY.md.

Where they agree

Recommendation Sources
Use a positive diagnostic strategy rather than exclusion, to shorten time to appropriate therapy ACG (Lacy 2021, PMID 33315591); BSG (Vasant 2021, PMID 33903147); NICE CG61 (https://www.nice.org.uk/guidance/cg61, accessed 2026-09-02); JSGE (Fukudo 2021, PMID 33538894)
Serologic testing for coeliac disease ACG suggests it in IBS with diarrhoea (Lacy 2021, PMID 33315591); BSG-aligned practice tests all patients regardless of stool form (Black 2020, PMID 32133113)
Faecal calprotectin in suspected IBS with diarrhoea, to rule out IBD ACG (Lacy 2021, PMID 33315591); Black 2020, PMID 32133113
Limited trial of a low-FODMAP diet for global symptoms ACG recommends (Lacy 2021, PMID 33315591); BDA dietetic guidance (McKenzie 2016, PMID 27272325)
Secretagogues for IBS-C (chloride channel activators, guanylate cyclase activators) ACG recommends (Lacy 2021, PMID 33315591); AGA strong for linaclotide, conditional for the rest (Chang 2022, PMID 35738724)
Rifaximin for IBS-D ACG recommends (Lacy 2021, PMID 33315591); AGA conditional, moderate certainty (Lembo 2022, PMID 35738725)
Gut-directed psychotherapy for global symptoms ACG suggests (Lacy 2021, PMID 33315591); BSG (Vasant 2021, PMID 33903147)
Gut–brain neuromodulators (tricyclics) for ongoing global symptoms or abdominal pain ACG, BSG, AGA (conditional, low certainty); supported by Khasawneh 2025, PMID 40258375
Alarm features trigger investigation and referral NICE CG61 (https://www.nice.org.uk/guidance/cg61, accessed 2026-09-02); JSGE recommends colonoscopy for one or more alarm symptoms/signs, risk factors or abnormal routine results (Fukudo 2021, PMID 33538894)

Where they disagree

Position Source
Conditional recommendation against, low certainty, in IBS-C Chang 2022, PMID 35738724
Conditional recommendation against, low certainty, in IBS-D Lembo 2022, PMID 35738725
SSRIs beat placebo for abdominal pain: RR 0.74 (0.56–0.99), 7 RCTs, 324 patients; review explicitly "highlights a potential for SSRIs to be modestly effective for abdominal pain" Khasawneh 2025, PMID 40258375
Earlier synthesis found "similar treatment effects for both tricyclic antidepressants and SSRIs," with heterogeneity among SSRI trials (I²=49%, p=0.07) Ford 2019, PMID 30177784

Both readings are defensible from the same data — the confidence interval touches unity and the trials are small — but the divergence is real, current, and unresolved. See gut-brain-neuromodulators.

2. Bile acid diarrhoea — test or don't

BSG-aligned practice guidance recommends SeHCAT in IBS-D, "a third of whom may actually have bile acid diarrhoea," and explicitly states there is no role for routine breath testing (Black 2020, PMID 32133113). ACG's guideline does not make bile-acid testing a routine step. The underlying prevalence (28.1%, 22.6–34.0 by SeHCAT <10%; Slattery 2015, PMID 25913530) and the treatment effect (sequestrants: stool consistency RR 1.50, 1.14–1.96; frequency RR 2.80, 1.68–4.67; Dilmaghani 2025, PMID 41090475) are not in dispute; test availability is — SeHCAT "is not widely available in many countries outside Europe and Canada" (Valentin 2016, PMID 26347530). This is a guideline disagreement generated by geography rather than by evidence. See differential-diagnosis-and-exclusion.

3. SIBO and breath testing

ACG maintains a dedicated SIBO guideline defining the entity and its testing (Pimentel 2020, PMID 32023228), and the North American Consensus sets breath-test thresholds (Rezaie 2017, PMID 28323273). BSG-aligned guidance states plainly: "There is no role for routine hydrogen breath tests for lactose malabsorption or small intestinal bacterial overgrowth" (Black 2020, PMID 32133113). Diagnostic thresholds themselves differ internationally: the Asia-Pacific criterion (hydrogen rise ≥12 ppm) diagnoses SIBO in 44.4% of IBS patients versus 37.8% by the North American criterion (≥20 ppm), and only the former tracked symptom severity in a prospective series (Loh 2026, PMID 42235989). See rifaximin-and-the-sibo-question.

4. Strength asymmetry between subtypes

Guideline Strong recommendations Conditional
AGA IBS-C (Chang 2022, PMID 35738724) 1 — linaclotide (high certainty) tenapanor, plecanatide, tegaserod, lubiprostone (moderate); PEG laxatives, tricyclics, antispasmodics (low); against SSRIs (low)
AGA IBS-D (Lembo 2022, PMID 35738725) 0 eluxadoline, rifaximin, alosetron (moderate); tricyclics, antispasmodics (low); loperamide (very low); against SSRIs (low)

The asymmetry mirrors the underlying trial evidence (constipation-predominant-pharmacotherapy versus diarrhoea-predominant-pharmacotherapy), not a difference in clinical need.

5. Formulary and availability

The Mexican position statement makes explicit what other guidelines leave implicit: recommendations are conditioned on what is available. It recommends antispasmodics (alone or combined) first-line for pain, loperamide for IBS-D diarrhoea, laxatives for IBS-C, 5-HT4 agonists (prucalopride, mosapride) in IBS-C, ondansetron in IBS-D, and notes that linaclotide is the only secretagogue available in Mexico; probiotics are conditionally recommended as adjuvants "due to heterogeneous evidence"; neuromodulators are second-line for pain; mesalazine may be used in IBS-D on weak evidence (Remes-Troche 2025, PMID 40307155). Ondansetron is recommended there and licensed nowhere for IBS (diarrhoea-predominant-pharmacotherapy). WGO's global guideline is built explicitly around resource-tiered cascades for the same reason (Quigley 2016, PMID 27623513).

6. The overlap gap

Only APAGE addresses IBS overlapping functional dyspepsia, building algorithms for FD-GERD, epigastric pain syndrome with IBS, postprandial distress syndrome with IBS and FD-constipation, on the premise that overlap "frequently occurs and has a negative impact on treatment outcomes" and that "there is a lack of guidance on their management" (Gwee 2023, PMID 36321167). Given that 34.6–55.3% of IBS patients also meet FD criteria (overlap-with-functional-dyspepsia), this is the largest unaddressed population in Western guidance.

Structural features worth noting

  • JSGE uses a stepped algorithm, unusual among these documents: step 1 is diet, behavioural modification and gut-targeted pharmacotherapy for 4 weeks; step 2 adds combinations of different gut-targeted agents and/or psychopharmacological agents plus basic psychotherapy for 4 weeks; step 3 combines gut-targeted pharmacotherapy, psychopharmacology and specific psychotherapy (Fukudo 2021, PMID 33538894).
  • BSG commissioned its own network meta-analyses to inform the guideline rather than relying on published syntheses (Vasant 2021, PMID 33903147) — the same Leeds group produces most of the meta-analyses cited throughout this knowledge base, which is a strength for consistency and a limitation for independence.
  • NICE positions IBS in primary care and frames referral as the exception, triggered by red flags (NICE CG61, https://www.nice.org.uk/guidance/cg61, accessed 2026-09-02). ATLANTIS was designed against that guidance and found that GPs infrequently prescribe the second-line treatment NICE already suggests (Ford 2023, PMID 37858323).
  • Guidelines are not followed. A qualitative study of GPs found IBS "an accepted illness, but management deviates from guidelines" (Harkness 2013, PMID 23805998).
  • Paediatric guidance is separate and recent: ESPGHAN/NASPGHAN 2025 for ages 4–18 (Groen 2025, PMID 40444524), with an Italian paediatric consensus (Di Nardo 2024, PMID 38486305) and a paediatric network meta-analysis of interventions (Sinopoulou 2025, PMID 40246358). This knowledge base is adult-scoped.

What no guideline currently addresses

  • Rome V. The criteria were published in May 2026 (Drossman 2026, PMID 42031435) and no society guideline retrieved in the 2026-09-02 audit had been revised against them. The dated PubMed/Europe PMC checks on 2026-10-14 did not supply a new comprehensive IBS management guideline for this catalogue. Their first accuracy study found lower sensitivity than Rome III or IV (66.1%; Staller 2026, PMID 42392123).
  • Open-label placebo, despite three positive randomised trials; the guideline registry was rechecked on 2026-09-02 (placebo-response-and-trial-design).
  • Sequencing diet against drugs. CARIBS showed dietary therapy outperforming optimised medical treatment (76%/71% vs 58%; Nybacka 2024, PMID 38643782) after the major guidelines were written.
  • Neuromodulator versus behavioural therapy in primary care — targeted PubMed and registry searches on 2026-09-02 retrieved no head-to-head trial, so no guideline can sequence them from direct comparative evidence.

Open questions

  • Should AGA's recommendation against SSRIs be revisited in light of Khasawneh 2025 (PMID 40258375)?
  • Should bile-acid testing be universal in IBS-D, and how should guidelines handle a test most of the world cannot access (Valentin 2016, PMID 26347530)?
  • Can guideline concordance on SIBO testing be reached while the diagnostic thresholds themselves differ by region (Loh 2026, PMID 42235989; Rezaie 2017, PMID 28323273)?
  • Will Rome V change any recommendation? Its performance profile differs from Rome IV (Staller 2026, PMID 42392123).
  • Why do guidelines not sequence diet before drugs, given CARIBS (Nybacka 2024, PMID 38643782)?
  • What would close the implementation gap? GPs deviate from guidance (Harkness 2013, PMID 23805998) and rarely prescribe the second-line drug NICE suggests (Ford 2023, PMID 37858323).

References

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