Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract, primarily comprising Crohn's disease and ulcerative colitis, characterized by periods of remission and relapse.

Definition

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract, primarily comprising Crohn's disease and ulcerative colitis, characterized by periods of remission and relapse.

Epidemiology

Prevalence higher in North America and Europe; rising in Asia and developing countries
Typically presents in adolescents and young adults (15–35 years)
Slight male predominance in Crohn’s disease; female predominance in ulcerative colitis
Genetic predisposition and family history increase risk
Environmental factors: smoking, diet, microbiome alterations, NSAID use

Etiology

Exact cause unknown; multifactorial
Genetic susceptibility: NOD2, IL23R, ATG16L1 mutations
Immune dysregulation: inappropriate mucosal immune response to intestinal microbiota
Environmental triggers: smoking (increases Crohn's risk, decreases UC risk), diet, stress, infections
Microbiome alterations contribute to chronic inflammation

Pathophysiology

Immune-mediated inflammation: Th1/Th17 dominant in Crohn’s disease, Th2 dominant in ulcerative colitis
Disruption of intestinal epithelial barrier leads to bacterial translocation
Chronic inflammation causes mucosal injury, ulceration, fibrosis, and strictures
Crohn’s disease: transmural inflammation, skip lesions, fistula formation
Ulcerative colitis: continuous mucosal inflammation starting in rectum, limited to colon