This narrative review examines the pathophysiology of irritable bowel syndrome (IBS), covering peripheral mechanisms (gut infection, microbiome changes, visceral hypersensitivity, intestinal permeability, mucosal inflammation, motility, serotonin, bile acid and carbohydrate metabolism) and central mechanisms (psychological health, altered central pain processing), integrated via the gut-brain axis.
No single definitive biomarker for IBS exists; however, some mechanisms—abnormal bile acid metabolism, accelerated colonic transit, and psychological comorbidity—can already be quantified with validated tests, while most others still lack reliable clinical translation.
This is a narrative review without systematic search methodology or meta-analytic synthesis, so selection bias in cited evidence is possible. No new primary data are presented, and most discussed mechanisms have not yet been translated into validated diagnostic tests or specific treatment targets.
Clinicians should consider IBS a disorder of gut-brain interaction driven by multiple overlapping mechanisms, not a single pathology. Where available, validated tools for bile acid malabsorption, colonic transit, and psychological comorbidity can guide targeted management today.
