Inflammatory Bowel Disease Overview

Inflammatory Bowel Disease (IBD)

• IBD is a chronic, relapsing, and remitting inflammatory disorder of the gastrointestinal (GI) tract
• Two main forms: Crohn's Disease (CD) and Ulcerative Colitis (UC)

Crohn's Disease (CD)

• Likely Cause: Unknown etiology, thought to be an aberrant immune response to gut microbiota in genetically susceptible individuals.
  • Genetic component: NOD2/CARD15 gene mutations on chromosome 16 are linked to CD. Genetic predisposition is supported by twin studies, where monozygotic twins have a higher concordance rate (42%-58%) than dizygotic twins (0%-5%).
  • Microbial Dysbiosis: Imbalance of gut microbiota plays a role in immune system activation.
  • Environmental factors: Smoking is a risk factor for Crohn's Disease, but may be protective for Ulcerative Colitis.
• Pathophysiology: Characterized by transmural inflammation (involving the full thickness of the GI wall).
  • Location: Can affect any part of the GI tract, most common in the terminal ileum and proximal colon.
  • Skip lesions: Areas of normal tissue between affected regions.
  • Immune response: Predominantly mediated by Th1 T helper cells that release TNF-α, recruiting inflammatory macrophages. Th17 T cells also contribute.
  • Tissue changes: Development of fistulas, perforations, abscesses, fibrosis and scar tissue formation leading to strictures and bowel obstruction.

Ulcerative Colitis (UC)

• Likely Cause: Similar to Crohn's, unknown etiology, thought to be an aberrant immune response.
  • Genetic and environmental factors.
• Pathophysiology: Characterized by continuous mucosal inflammation (involving only the mucosa and submucosa, not transmural).
  • Location: Begins in the rectum and extends proximally in a continuous pattern throughout the colon.
  • Nature of inflammation: Affects only the mucosa and submucosa.

Disease Transmission

• Not transmissible; IBD is a non-communicable disease.

Risk Factors

• Genetic: Genetic predisposition, NOD2/CARD15 mutations
• Environmental: Smoking (increases CD risk, paradoxical protection in UC), diet (high in sugar and refined carbohydrates), microbial dysbiosis (disruption of gut flora), antibiotic use
• Lifestyle: Geographical location (higher prevalence in developed countries), race/ethnicity (higher in some populations)
  • Hygiene hypothesis: improved sanitation may reduce exposure to infectious agents, potentially leading to an overactive immune system, contributing to IBD.

Clinical Manifestations

• Crohn's Disease: Abdominal pain (usually in the right lower quadrant), diarrhea (often non-bloody), formation of fistulas, abscesses, strictures, nutritional deficiencies.
• Ulcerative Colitis: Diarrhea (often bloody, purulent mucus), cramping pain (usually lower left quadrant), bowel urgency and tenesmus, fever, anemia, and weight loss.

Explore the essentials of Inflammatory Bowel Disease (IBD), focusing on Crohn's Disease and Ulcerative Colitis. Understand the possible causes, genetic factors, and the impact of microbial dysbiosis. This quiz delves into the complexities of GI tract inflammation and its implications.