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Irritable bowel syndrome (IBS)
IBS is a positive diagnosis by the Rome IV criteria — recurrent abdominal pain linked to bowel movements — not a diagnosis of exclusion; without alarm features limited testing is enough (blood count, CRP, coeliac serology and sometimes calprotectin), and treatment is chosen by subtype: constipation, diarrhoea or mixed.
Why it matters in the exam
The typical question presents a young woman with abdominal pain and bloating that improve after a bowel movement, with a change in stool frequency or form, without weight loss and without blood. The candidate must remember the Rome IV criteria: pain on average once a week or more during the past 3 months, plus two or more of: a link to defecation, a shift in stool frequency, a shift in stool form — with symptoms that began 6 or more months before diagnosis. A standard distractor: sending every patient for colonoscopy — not needed in the absence of alarm features.
Alarm features that require investigation: age 45 or older with new symptoms, weight loss, blood in the stool, iron deficiency anaemia, symptoms that wake the patient from sleep, fever, and a family history of bowel cancer, IBD or coeliac disease. In treatment: explanation and reassurance, a low-FODMAP diet, soluble fibre (psyllium), antispasmodics; for constipation — PEG or linaclotide; for diarrhoea — loperamide or rifaximin; and for persistent pain — a low-dose tricyclic antidepressant and cognitive behavioural therapy. Faecal calprotectin helps separate diarrhoea-predominant IBS from IBD.
Key points
- Rome IV: pain one day a week for 3 months + 2 of 3 (defecation, frequency, form).
- Without alarm features: blood count, CRP, coeliac, and calprotectin with diarrhoea.
- Alarm features: age 45 or older, weight loss, blood, anaemia, night, family.
- Constipation: psyllium, PEG, linaclotide; diarrhoea: loperamide, rifaximin.
- Persistent pain: low-dose tricyclic and cognitive behavioural therapy.
Summary table
| Topic | Criterion | Action | Exam note |
|---|---|---|---|
| Rome IV | Weekly pain for 3 months + 2 of 3: defecation, frequency, form | Positive diagnosis | Began 6 or more months earlier |
| Minimal work-up | No alarm features | Blood count, CRP, coeliac; calprotectin with diarrhoea | No routine colonoscopy |
| Alarm features | Age 45 or older, weight loss, blood, anaemia, night symptoms, family history | Colonoscopy and work-up | Not IBS until excluded |
| IBS with constipation | Hard stool, straining | Psyllium, PEG, linaclotide | Insoluble fibre worsens bloating |
| IBS with diarrhoea | Loose stool, urgency | Loperamide, rifaximin, low-FODMAP diet | Exclude coeliac disease and IBD |
| Persistent pain | All subtypes | Low-dose tricyclic, cognitive behavioural therapy | Gut-brain axis |
In the full version for subscribers
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Sources
- ACG Clinical Guideline: Management of Irritable Bowel Syndrome, 2021 — Positive diagnosis, limited testing and treatment by subtype
- Rome IV Criteria for Functional Gastrointestinal Disorders, 2016 — Irritable bowel syndrome
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Irritable Bowel Syndrome
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.