Skip to main content
DigestOk
Conditions / IBS

Irritable Bowel Syndrome (IBS)

A complex functional gastrointestinal disorder affecting up to 10-15% of the global population.

What is IBS?

IBS is characterized by chronic abdominal pain and altered bowel habits in the absence of any detectable structural or biochemical abnormalities (like ulcers or inflammation). Because there is no single biomarker for IBS, it is diagnosed clinically using the Rome IV Criteria.

The Rome IV Diagnostic Criteria (2016)

Recurrent abdominal pain, on average, at least 1 day per week in the last 3 months, associated with two or more of the following criteria:

  • Related to defecation.
  • Associated with a change in frequency of stool.
  • Associated with a change in form (appearance) of stool.

*Criteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

IBS Subtypes

Treatment protocols vary wildly depending on the dominant symptom profile, classified using the Bristol Stool Scale:

  • IBS-C (Constipation-predominant): >25% of bowel movements are Bristol Types 1-2, and <25% are Types 6-7.
  • IBS-D (Diarrhea-predominant): >25% of bowel movements are Bristol Types 6-7, and <25% are Types 1-2.
  • IBS-M (Mixed): >25% of bowel movements are Types 1-2, AND >25% are Types 6-7.

Proposed Mechanisms (The "Why")

While historically dismissed as purely psychological ("all in your head"), modern gastroenterology recognizes IBS as a disorder of the gut-brain interaction (DGBI). Current leading theories include:

  1. Visceral Hypersensitivity: The nerves in the gut wall are overly sensitive to normal amounts of gas or stretching, translating normal digestion into pain.
  2. Post-Infectious IBS (PI-IBS): Up to 10-30% of patients develop IBS following an acute bout of food poisoning (gastroenteritis), leading to low-grade neural inflammation and changes in motility.
  3. Microbiome Dysbiosis: Altered ratios of gut bacteria compared to healthy controls (often lower diversity).

Clinical Management Protocols

Management must be tailored to the subtype and severity.

Dietary Intervention

The Low FODMAP diet is currently the most evidence-based first-line therapy, effective in up to 70% of patients for symptom control.

Neuromodulators

Low-dose tricyclic antidepressants (TCAs) or SSRIs are frequently used not for depression, but to dampen the hypersensitive nerve signals between the gut and the brain.