Inflammatory Bowel Disease (IBD)

Aetiology:** Complex interplay of genetic predisposition (e.g., NOD2 gene mutations), dysregulated immune response to gut microbiota, and environmental triggers (e.g., diet, smoking, antibiotics).

Pathophysiology:**

• Crohn’s disease: Transmural inflammation that can affect any part of the GI tract (mouth to anus), often discontinuously (“skip lesions”).
• Ulcerative colitis: Continuous mucosal inflammation limited to the colon, starting at the rectum.

Common symptoms:**

• Diarrhoea (often bloody in UC, watery in CD).
  Abdominal pain/cramping (more focal in CD, left-sided in UC).
  Urgency, tenesmus (especially in UC).
• Weight loss, fatigue, and fever.

Extra-intestinal manifestations:**

• Joints (arthralgia/arthritis), skin (erythema nodosum, pyoderma gangrenosum), eyes (uveitis, episcleritis).

Red-flag symptoms:**

• Severe abdominal pain, persistent vomiting (suggesting obstruction or toxic megacolon).
• Profuse bleeding, unexplained weight loss, and signs of sepsis.

Clinical assessment:** Detailed history (symptom pattern, family history), physical exam (abdominal tenderness, perianal disease in CD).

Laboratory tests:**

Fecal calprotectin (to distinguish from IBS).

• CBC (anemia, leukocytosis), CRP/ESR (inflammation), albumin (nutritional status).
• Serology (e.g., ASCA, pANCA; supportive but not diagnostic).

Endoscopy with biopsy (gold standard):**

• Colonoscopy: For visual assessment and histologic confirmation (crypt abscesses in UC, granulomas in CD).
• Cross-sectional imaging: MRI enterography/CT enterography (for small bowel involvement in CD).
• Capsule endoscopy: For suspected small bowel CD.

Induction of remission:**

• Mild-moderate: Aminosalicylates (e.g., mesalamine; primarily UC), corticosteroids (budessonide/systemic).
• Moderate-severe: Biologics (anti-TNF agents like infliximab/adalimumab, anti-integrins, anti-IL-12/23), immunomodulators (thiopurines, methotrexate).

Maintenance therapy:**

• Immunosuppressives/biologics to prevent relapse.
• Dietitian support (e.g., exclusive enteral nutrition in CD).

Surgical options:**

• UC: Colectomy (curative).
• CD: Stricturoplasty, resection for complications (obstruction, fistulae).

• Local:**
• Strictures, fistulae, abscesses (CD).
• Toxic megacolon, perforation (UC).
• Malnutrition, growth failure (in pediatric IBD).**
• Increased risk of colorectal cancer (long-standing UC/extensive CD).**
• Bone loss (osteoporosis/osteopenia).**

Prevention:** No known prevention; smoking cessation reduces CD risk/flares.

Follow-up:**

• Regular monitoring of disease activity (symptoms, biomarkers, endoscopy).
• Vaccinations (avoid live vaccines on immunosuppressants).
• Bone density screening, dermatologic/ophthalmic exams for extra-intestinal manifestations.
• Colonoscopic surveillance for dysplasia in long-standing colitis.