IBS and Functional Bowel
Rome IV positive diagnosis, low-FODMAP Monash 3-phase, rifaximin retreatment criteria, eluxadoline (and the post-cholecystectomy contraindication), alosetron REMS, ATLANTIS TCA dosing for visceral hypersensitivity, and the CBT delivery channels the boards now recognize.
- Audio chapterSingle-voice audio, listen on the commute.
- ABIM-format MCQs5-option vignettes with full wrong-answer teaching.
- Study guideTables, decision trees, primary sources.
- AI tutorChapter-grounded, answers the question you're stuck on.
What this chapter covers
- Section 13.1: Definition and Rome IV diagnosis
Irritable bowel syndrome is a positive clinical diagnosis built on a stereotyped symptom pattern, not a diagnosis of exclusion that emerges only after every organic possibility has been chased to ground.
- Section 13.2: Pathophysiology
IBS is a disorder of brain-gut interaction, and the pathophysiology is multifactorial because the symptom syndrome captures patients who arrive at the same final phenotype through different upstream mechanisms.
- Section 13.3: IBS-C treatment
IBS-C treatment is layered, and the layers correspond to escalating mechanism-targeted intervention.
- Section 13.4: IBS-D treatment
IBS-D treatment, like IBS-C, is layered, but the mechanisms targeted are different and several of the drugs carry meaningful safety considerations.
- Section 13.5: All-subtype treatments
Several therapies work across IBS subtypes because they target shared mechanisms (visceral hypersensitivity, central pain processing, the brain-gut axis) that are not subtype-specific.
- Section 13.6: Bloating and pharmacology summary
Bloating is the symptom IBS patients report as most bothersome, and it splits into two ideas that must be kept separate.
Podcast episodes
- 01
ROME IV Pathophys IBS C
Episode one of two on Irritable Bowel Syndrome and functional bowel, covering positive diagnosis, Rome IV criteria, and subtyping. It maps the brain-gut model and its five mechanisms onto the drug classes. It closes with the mechanism-targeted pharmacology of constipation-predominant IBS.
Read the transcript → - 02
IBS D Neuromod Bloating
Episode two of the IBS and Functional Bowel chapter covers the diarrhea-predominant subtype, the neuromodulators and behavioral therapies that work across subtypes, and the mechanistic workup of bloating. Drug selection is mechanism-matched to the dominant symptom and driver, not subtype-matched in the abstract. Carry mechanism, subtype indication, and contraindication together to pick the right answer.
Read the transcript →
Key topics
- Rome IV positive diagnosis
- IBS subtyping by Bristol form
- Alarm features and targeted testing
- IBS-D differential and mimics
- Brain-gut five-mechanism model
- Visceral hypersensitivity
- IBS-C secretagogues
- Prucalopride prokinetic
- IBS-D pharmacology
- Loperamide, rifaximin, eluxadoline
- Bile acid sequestrants and alosetron
- Neuromodulators by side-effect match
- Antispasmodics and peppermint oil
- Behavioral and mind-body therapy
- Bloating versus distension
- Low-FODMAP diet and fiber
Sources
Guidelines, consensus statements, and validated instruments this chapter draws on. Named here because the chapter applies them directly.
Professional society guidelines
- American Gastroenterological Association (AGA)
Classification and diagnostic criteria
- Rome IV criteria (functional GI disorders)
Scoring systems
- Child-Pugh score