Table of Contents
Overview – Inflammatory Bowel Diseases
Inflammatory bowel diseases (IBD) encompass two major chronic autoimmune conditions affecting the gastrointestinal tract: Crohn’s disease and ulcerative colitis. These disorders are marked by recurrent inflammation due to dysregulated immune responses to gut flora, leading to a wide range of intestinal and extra-intestinal manifestations. While the exact cause remains unclear, genetic susceptibility, lifestyle factors, and environmental triggers play important roles. Understanding the key differences between Crohn’s and UC is crucial for diagnosis, management, and anticipating complications.
Definition
- Inflammatory bowel disease (IBD) = umbrella term for:
- Crohn’s disease
- Ulcerative colitis
- Both are chronic, relapsing-remitting autoimmune conditions affecting the GI tract.
Aetiology
- Multifactorial:
- Genetics + Autoimmunity (15% with family history)
- Smoking: ↑ Risk in Crohn’s, ↓ Risk in UC
- Western lifestyle, diet
- Appendectomy → protective for UC
- Breastfeeding → protective for Crohn’s
Pathophysiology
- Genetic predisposition → inappropriate immune response to commensal gut flora
- Leads to excessive chronic inflammation of intestinal mucosa
- In Crohn’s: transmural, patchy inflammation
- In UC: mucosal, continuous inflammation
Clinical Features
Intestinal Symptoms (Common to both)
- Abdominal pain, cramping
- Vomiting and/or diarrhoea
- Rectal bleeding
Extra-Intestinal Manifestations
- Arthritis
- Skin: pyoderma gangrenosum
- Eye: uveitis, episcleritis
- Hepatobiliary: primary sclerosing cholangitis
Distinguishing Features
| Feature | Crohn’s Disease (CD) | Ulcerative Colitis (UC) |
|---|---|---|
| Location of Onset | Terminal ileum | Rectum |
| GIT Involvement | Anywhere mouth → anus | Colon only |
| Anus Involvement | Common | Rare |
| Distribution | Patchy (skip lesions) | Continuous |
| Inflammation Depth | Full thickness | Mucosa only |
| Stool Appearance | Porridge-like, may have steatorrhea | Bloody, mucousy |
| Tenesmus | Uncommon | Common |
| Fever | Common | Uncommon |
| Fistulae | Common | Rare |
| Weight Loss | Common | Less common |
Morphology
- Crohn’s: transmural inflammation, skip lesions, granulomas
- UC: superficial mucosal ulceration, continuous from rectum proximally
Investigations
- Colonoscopy + Biopsy = gold standard
- Imaging: CT/MRI enterography (Crohn’s), AXR (Toxic Megacolon)
- Bloods: inflammatory markers, anaemia, CRP, ESR
- Faecal calprotectin for monitoring inflammation
Management
- Medical
- Corticosteroids (e.g. prednisone) for flare control
- DMARDs and biologics (e.g. infliximab, adalimumab)
- Immunomodulators (e.g. azathioprine, methotrexate)
- 5-ASA (e.g. sulfasalazine – esp. in UC)
- Surgical
- Indicated in ~75% of Crohn’s patients
- ~20% of UC patients require colectomy
- Surveillance
- Annual colonoscopy to screen for colorectal cancer
Complications
- Toxic Megacolon – UC > Crohn’s
- Bowel Perforation – Crohn’s
- Fistulae & Anal Fissures – Crohn’s
- Colorectal Cancer – ↑ risk in both, esp. long-standing disease
- Malabsorption – Crohn’s due to small bowel involvement
Summary – Inflammatory Bowel Diseases
Inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis, are chronic autoimmune conditions affecting the gut with both intestinal and extra-intestinal complications. Recognising their distinct patterns—transmural and patchy in Crohn’s, mucosal and continuous in UC—is essential for diagnosis and management. For more gastrointestinal conditions, see our Gastrointestinal Overview page.