Place · Level 3

Irritable Bowel Syndrome

全球 5-10% · Rome IV 分型 IBS-D/C/M · 低 FODMAP 三阶段 · 肠脑轴 · SIBO 测试陷阱 · 红旗清单

Story path

1Rome IV · 4 subtypesRome IV · 4 subtypes
2Low FODMAP · 3 phasesLow FODMAP · 3 phases
3Gut-brain · microbiomeGut-brain · microbiome
4SIBO tests + drugsSIBO tests + drugs
5Decision tree + atlas closureDecision tree + atlas closure

Chapter 1

Rome IV · 4 subtypes

Irritable Bowel Syndrome (IBS) is a functional bowel disorder: structurally the intestine has no visible lesion, but motility / sensation / microbiome / gut-brain axis goes wrong. Globally affects 5-10% of adults, women ~2× men, average diagnostic delay 4 years.

Rome IV criteria (2016)

Core: recurrent abdominal pain, averaging at least 1 day/week, for ≥3 months (onset ≥6 months prior), plus ≥2 of:

Related to defecation (before / after / no change)Associated with change in stool frequencyAssociated with change in stool form
4 subtypes (by Bristol stool scale):

IBS-D (diarrhea): >25% loose/watery, <25% hardIBS-C (constipation): >25% hard, <25% loose/wateryIBS-M (mixed): both loose/watery and hard >25%IBS-U (unclassified): doesn't fit above
Key: IBS is a diagnosis of exclusion

Must rule out: IBD (ulcerative colitis / Crohn's) / lactose intolerance / celiac disease / microscopic colitis / colorectal cancerBasic blood: CBC + + celiac antibodies (tTG-IgA) + Stool: occult blood + (age 40+) calprotectinColonoscopy: age 50+ / family history / red flags
Why a dedicated atlas island?

Severely undertreated: 50% of patients never see a doctor, 60% use OTC ineffectivelyDietary intervention (low FODMAP) actually works, but is extensively misreported (next scene)Marketing hotbed for 'SIBO testing ads' + 'candida detox' + 'leaky gut syndrome'

Red flags — not IBS

These symptoms aren't IBS — see a doctor immediately:

Blood in stool / melenaUnexplained weight loss (>5% in 6 months)Nocturnal abdominal pain waking from sleepProgressive dysphagiaPersistent feverNew symptoms after age 50Colorectal cancer / IBD family historyIron-deficiency anemiaFecal calprotectin >100 µg/g
Any positive → see gastroenterology for colonoscopy + further imaging evaluation.

'IBS workup checklist' standard (ACG 2021):

No red flags + Rome IV met + basic exclusion negative, in those under 50, routine colonoscopy or imaging is usually not needed'Colonoscopy to be sure it's not IBD' is usually not necessaryOver-testing produces anxiety + healthcare waste + incidental non-clinical findings driving further tests

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Chapter 2

Low FODMAP · 3 phases

Low FODMAP diet is the only A-grade evidence dietary intervention for IBS (Halmos 2014 *Gastroenterology* + multiple meta-analyses).

What FODMAPs are:

Fermentable Oligosaccharides Disaccharides Monosaccharides And Polyols.

These sugars are incompletely absorbed in the small intestine, reach the colon and get fermented by bacteria, producing gas + osmotic water pull.

F-Oligo: fructans (wheat / onion / garlic), GOS (legumes)D-Disaccharide: lactose (dairy, especially in lactose intolerant)M-Monosaccharide: excess fructose (honey / apples / HFCS)Polyol: sorbitol / mannitol (sugar-free gum + cherries + mushrooms)
Key: these aren't 'bad foods'

Most are very healthy foods (onions / garlic / apples / whole grains / legumes / dairy). IBS patients are sensitive to FODMAPs — FODMAPs themselves aren't toxic. The general population should NOT go low FODMAP.

Three-phase protocol (Monash University)

Phase 1 · Strict elimination (2-6 weeks):

Strictly avoid all high-FODMAP foodsGoal: see whether symptoms improve (~70% of IBS patients show significant improvement)Not lifelong: this phase isn't sustainable, has nutritional risk
Phase 2 · Systematic reintroduction (6-8 weeks):

Introduce 1 FODMAP class per week, dose gradually increasesGoal: identify your own trigger foods + thresholdMost patients find they're only sensitive to 2-3 classes, not all
Phase 3 · Personalized long-term diet:

Avoid your own triggersEat tolerated FODMAPs normallyThis is the lifelong sustainable phase — more nutrient-rich and less mentally taxing than Phase 1
Why most people 'fail at low FODMAP'

Stuck in Phase 1: long-term strictness leads to malnutrition + anxiety + social difficultiesNo dietitian guidance, hard to self-do correctlyWrong expectation, thinking it's a long-term diet like keto
Practical

Find a gastroenterologist + FODMAP-trained dietitianUse the Monash FODMAP app (official, $9, globally recognized)Complete the full protocol in 3-6 months, arriving at personalized daily dietIf you fail or don't improve, consider other causes (SIBO / microscopic colitis / anxiety-driven)

Myth · 'stay on low FODMAP forever'

Low FODMAP is the only A-grade evidence dietary intervention for IBS, but it's also the most badly misused — most 'low FODMAP failures' are really the wrong way of doing it, not a failure of the method.

The commonest error is treating it as a lifelong diet, getting stuck in the strict elimination first phase. That is exactly what this protocol should not do:

Phase 1 (strict elimination) is a diagnostic tool, not the treatment endpoint: its only purpose is to see whether symptoms improve (~70% do); it isn't sustainable in itself and long term brings malnutrition, anxiety, and social difficulty. It should last only 2-6 weeks.The actual treatment is Phase 2 (systematic reintroduction): introduce one FODMAP class per week at gradually rising doses to find your own trigger foods and tolerance thresholds. Most people discover they're only sensitive to 2-3 classes, not all.The lifelong stage is the personalized Phase 3: avoid only your own triggers, eat tolerated ones normally. It's far more nutrient-rich and far less mentally taxing than Phase 1.
One more thing to correct: these high-FODMAP foods (onion, garlic, apple, whole grains, legumes, dairy) are mostly very healthy foods, not 'bad foods'. IBS patients are sensitive to FODMAPs — FODMAPs aren't toxic — so people without IBS should not go low FODMAP, as it just needlessly cuts out a pile of beneficial foods.

A few practices that make it actually work:

Find a FODMAP-trained dietitian — the three phases are hard to do right by yourself.Use the official Monash FODMAP app for food ratings — the globally recognized tool.Treat the whole process as a 3-6 month 'find your triggers' project, ending in a personalized daily diet, not an ever-shrinking list of forbidden foods.
If you complete the full protocol and still don't improve, don't keep grinding on food — go back and consider other causes (SIBO / microscopic colitis / anxiety-driven) rather than stretching the elimination phase indefinitely.

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Chapter 3

Gut-brain · microbiome

IBS isn't just an 'intestinal problem' — it also involves the gut-brain axis.

Four gut-brain axis pathways (atlas `digestive/microbiome` L4 covers in detail):

1. Vagus nerve: bidirectional, 90% of signals go gut → brain
2. axis (stress + cortisol)
3. Immune cytokines (5-HT / etc.)
4. Microbial metabolites ( / neurotransmitters / bile acids)

The IBS-stress relationship

About 70% of IBS patients have comorbid anxiety / depression / PTSD history. Stress activates mast cells, increases gut permeability, alters motility. This isn't a 'psychological problem' — it's real gut-brain circuit dysregulation. CBT / GI-specific CBT (GI-CBT) + hypnotherapy are B-to-A grade evidence, comparable to drugs.

Microbiome

IBS patients show decreased microbial diversity, reduced anaerobesBifidobacterium + Faecalibacterium are usually lowBut causal direction is unclear — don't know if cause or result
Probiotics (atlas `probiotics` covers in detail)

Strain specificity is strong — not 'any probiotic works'.

B-grade evidence:*Bifidobacterium infantis* 35624 (Align)Multi-strain VSL#3 (has brand-specific data)*L. plantarum* 299vC-grade / no evidence: regular yogurt, most cheap OTC multi-strain productsNot recommended for: severe pancreatitis, severely immunocompromised (Besselink 2008 PROPATRIA *Lancet*, mortality ×2)Usually try 4-8 weeks, stop if no improvement
SCFA + fiber

Soluble fiber (psyllium): A-grade first-line for IBS-CInsoluble fiber (wheat bran): can actually worsen symptoms (gas)Avoid high-dose multi-fiber combinations
FMT (fecal microbiota transplant)

A-grade for *C. difficile* indication (van Nood 2013 *NEJM*)For IBS: most RCTs negative or marginal (El-Salhy 2020 is one of few positives, poor replication)Not recommended IBS treatment
Useless / marketing traps

'Candida detox / leaky gut syndrome': no evidence base'Heavy metal detox': no evidence base'Parasite detox': no evidence base'Enzyme + detox supplements' (Plexus / Le-Vel / Beachbody and other MLM)

Myth · 'leaky gut / detox' and 'any probiotic'

IBS is one of the densest fields for marketing traps, because the symptoms are real and there's no single miracle drug long term — which leaves room for 'leaky gut / detox / probiotics cure-all' pitches. Let's check the evidence point by point.

Several concepts with no evidence base:

'Leaky gut syndrome': the gut barrier function is real and does change in some conditions, but as a standalone diagnosis that explains all symptoms and needs a dedicated 'repair protocol', it has no evidence base.'Candida detox', 'heavy-metal detox', 'parasite detox': equally no evidence base. Healthy liver and kidneys already continuously clear metabolic waste — there's no 'toxin' requiring a purchased product to 'flush'.'Enzyme + detox combo supplements' (common in MLM brands): bundle the above concepts into a personalized package, charging for chronic-disease anxiety, not efficacy.
On probiotics, real and fake are mixed and need separating:

Not 'any probiotic works': probiotic effects are strain-specific. B-grade evidence exists for specific strains (e.g. Bifidobacterium infantis 35624 / multi-strain VSL#3 / L. plantarum 299v), while regular yogurt and most cheap OTC multi-strain products are C-grade or no evidence.Use: usually trial for 4-8 weeks, stop if no improvement, don't take indefinitely.Who to be careful with: severe pancreatitis and the severely immunocompromised should not use them (in PROPATRIA, the probiotic arm's mortality doubled). Probiotics are not 'absolutely safe, more is better'.
On FMT (fecal microbiota transplant): it's A-grade effective in C. difficile infection, but in IBS most RCTs are negative or marginal with poor replication — currently not a recommended IBS treatment. Don't get pulled along by 'swap the gut bacteria, cure everything'.

In one line: IBS is real, but the solution is a combined toolkit of evidence-based gastroenterology + dietitian + psychotherapy when needed — not some detox package or a bottle of cure-all probiotics. When you see 'personalized complex protocol + recurring fees', it's mostly selling anxiety.

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Chapter 4

SIBO tests + drugs

SIBO (Small Intestinal Bacterial Overgrowth) is the most commercialized and most controversial part of the IBS topic.

What real SIBO is

Normally the small intestine has <10⁵ CFU/mL of bacteria (the colon has 10¹¹)SIBO: abnormal large bacterial migration into the small intestine — fermentation happens where it shouldn't, causing bloating + gas + nutrient absorption impairmentTrue indications: short bowel syndrome / intestinal dysmotility (diabetic autonomic neuropathy / scleroderma) / recurrent diarrhea + low B12 + fat malabsorptionSIBO proportion in true IBS patients: 30-80% (range is this wide because diagnostic methods are inconsistent)
Problems with SIBO testing

Breath testing (glucose or lactulose hydrogen breath test) isn't the gold standard: compared to small intestinal aspiration culture, sensitivity 50-70%, specificity 60-80%High false positive rate: rapid intestinal transit (positive without SIBO); lactulose has higher false positives than glucoseSmall intestinal aspiration is the true gold standard, but highly invasive + rarely done'Home SIBO test kit' for $300-500: results can't distinguish true SIBO from general IBS bloating
SIBO treatment (if confirmed)

Rifaximin is a non-absorbed intestinal antibioticA-grade RCT (Pimentel 2011 *NEJM* TARGET): IBS-D patients 14-day course, ~41% improvement vs 32% placeboSystemic absorption <0.4%, good safety profileHigh recurrence rate: 40-60% within 6 months, needs repeatingCost: 14-day course $1500-2000 (US, usually requires insurance approval)Neomycin + Rifaximin: combination regimen for methane-producing SIBODiet: avoid high FODMAP during SIBO + restrict fermentable carbs
'SIBO clinic' marketing traps

Not based on Rome / red flag screening, directly sells breath test + personalized 'complex antibiotic / herbal regimens''Berberine + neem + oregano oil': no RCT evidence, and not safe (atlas `berberine` covers in detail)'6-month repeat treatment retainer fee': chronic disease billing modelCorrect path: gastroenterology + selective testing + Rifaximin prescription
IBS drugs (non-SIBO)

IBS-C:Linaclotide (Linzess) / Lubiprostone (Amitiza) / Plecanatide / Tenapanor: A-gradePEG (polyethylene glycol): B-grade, cheapIBS-D:Eluxadoline (Viberzi) / Alosetron (Lotronex, female-only): A-gradeLoperamide: short-term useRifaximin: as aboveAbdominal pain:Antispasmodics (hyoscine / dicyclomine): B-grade (low-dose amitriptyline / nortriptyline): B-grade, works on neuropathic pain pathwaySSRI: useful when anxiety + IBS are comorbid

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Chapter 5

Decision tree + atlas closure

4-week self-check + 6-month management path

Week 1 · Rule out red flags + see a doctor

If any red flag is positive, see gastroenterology immediatelyIf no red flags, family doctor runs basic workup (CBC + + tTG-IgA + + calprotectin)Use Rome IV self-assessment (atlas description + Monash app)
Weeks 2-3 · Lifestyle baseline

Regular three meals, avoid single large mealIf sensitive, limit alcohol + limit coffeeEat slowly, no screens at the table30 min walk daily helps motilityStress management (CBT / mindfulness / diaphragmatic breathing)
Week 4 · Start FODMAP Phase 1 (if needed)

Find a FODMAP dietitian2-6 weeks strict elimination phaseMonash app is essentialDon't go it alone
Months 2-4 · FODMAP reintroduction

1 class per weekFind personal triggersDietitian follow-up
Month 6 · Personalized stable diet

Avoid your triggersEat tolerated foods normallyNo more strict FODMAP
Still symptomatic, see gastroenterology + medications / SIBO evaluation. Don't go to SIBO clinics — find an evidence-based GI specialist, use selective medications (covered in previous scene).

Atlas + report loop

Report engine `fiber-microbiome` / `ibs-suspect` rules link back here. Atlas links to:

`digestive/microbiome` L4 — + gut-brain axis`probiotics` L3 + L4 — strains + gastric acid massacre`carbs-fiber` L3 — soluble vs insoluble fiber`insomnia/what-types` L4 — stress / comorbidity`berberine` L3 — 'herbal SIBO treatment' debunked
Bottom line

IBS is a real disease, not 'making a fuss'. Most patients can be managed to normal quality of life, but it requires a multi-faceted toolkit combination — not a single miracle drug. Don't follow the SIBO clinic / candida detox / leaky gut syndrome marketing path. Find evidence-based gastroenterology + dietitian + psychotherapy when needed.

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