Inflammatory Bowel Disease (IBD)

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Referral

Definition

Inflammatory Bowel Disease (IBD) is a group of chronic, relapsing, and remitting inflammatory conditions of the gastrointestinal tract, primarily including Crohn’s disease and ulcerative colitis (UC).

Aetiology

The exact cause of IBD is unknown, but it is thought to result from an inappropriate immune response to intestinal microbiota in genetically susceptible individuals. Key factors include:

  • Genetic predisposition (e.g., NOD2 mutations in Crohn’s disease).
  • Environmental triggers (e.g., diet, smoking, infections).
  • Imbalance of gut microbiota (dysbiosis).
  • Abnormal immune responses causing chronic inflammation.

Pathophysiology

  • Crohn’s disease: this is a transmural inflammation affecting any part of the gastrointestinal tract, often with skip lesions and granulomas.
  • Ulcerative colitis: inflammation limited to the mucosa of the colon and rectum, starting distally and progressing proximally in a continuous pattern.

Risk factors

  • Family history of IBD.
  • Smoking:
    • Increases risk of Crohn’s disease.
    • Decreases risk of ulcerative colitis.
  • Urban living and higher socioeconomic status.
  • Western diet (high in processed foods and low in fibre).
  • Non-steroidal anti-inflammatory drug (NSAID) use.

Signs and symptoms

Common Symptoms:

  • Diarrhoea (may be bloody in ulcerative colitis).
  • Abdominal pain (crampy in Crohn’s disease).
  • Weight loss and malnutrition.
  • Fatigue and malaise.
  • Rectal bleeding (more common in ulcerative colitis).

Signs:

  • Abdominal tenderness (especially in the right lower quadrant in Crohn’s disease).
  • Pallor (indicating anaemia).
  • Perianal disease (e.g., abscesses, fistulas in Crohn’s disease).
  • Extra-intestinal manifestations:
    • Arthritis.
    • Erythema nodosum or pyoderma gangrenosum (skin).
    • Uveitis or episcleritis (eyes).
    • Primary sclerosing cholangitis (liver).

Investigations

  • Blood tests:
    • Full blood count (FBC): may show anaemia or raised white cell count.
    • CRP and ESR: elevated, indicating inflammation.
    • Liver function tests: to rule out for primary sclerosing cholangitis.
  • Faecal calprotectin: marker of intestinal inflammation to distinguish IBD from irritable bowel syndrome (IBS).
  • Imaging:
    • Abdominal X-ray: to assess for colonic dilatation (toxic megacolon).
    • CT/MRI: for complications such as strictures, fistulas, or abscesses in Crohn’s disease.
  • Endoscopy:
    • Colonoscopy: gold standard for diagnosis, with biopsy for histological confirmation.
    • Capsule endoscopy: useful for small bowel Crohn’s disease.

Management

1. Induction of Remission (usually initiated by a specialist):

  • Aminosalicylates: e.g., mesalazine for mild to moderate ulcerative colitis.
  • Corticosteroids: prednisolone for moderate to severe disease, short-term use only.
  • Biologic therapy: anti-TNF agents (e.g., infliximab) for severe or refractory cases.

2. Maintenance of Remission:

  • Immunosuppressants: azathioprine or mercaptopurine.
  • Aminosalicylates: continued use in ulcerative colitis.
  • Biologic therapy: anti-TNF agents or newer agents (e.g., vedolizumab).

3. Nutritional Support:

  • Dietary modifications to address malnutrition and deficiencies.
  • Exclusive enteral nutrition (especially in children with Crohn’s disease).

4. Surgical Management:

  • Ulcerative colitis: total colectomy can be curative.
  • Crohn’s disease: resection of affected segments for complications (e.g., strictures, fistulas).

Referral

  • Urgent referral for severe symptoms or complications (e.g., toxic megacolon, severe bleeding).
  • Specialist referral for biologic therapy initiation or surgical management.
  • Gastroenterology follow-up for disease monitoring and optimisation of therapy.
GastroenterologymypanotesInflammatory Bowel Disease (IBD)