Inflammatory bowel disease

Introduction

Inflammatory Bowel Disease (IBD) refers to a group of chronic inflammatory conditions affecting the gastrointestinal (GI) tract. The two main types are Ulcerative Colitis (UC) and Crohn’s Disease. Although they share overlapping symptoms, they differ in location, pattern of inflammation, complications, and management.

Location of Disease

• Ulcerative Colitis
  • Involves only the colon and rectum.
  • Inflammation always starts at the rectum and extends proximally in a continuous manner.
• Crohn’s Disease
  • Can affect any part of the GI tract, from mouth to anus.
  • Most commonly involves the terminal ileum.

Pattern of Inflammation

• Ulcerative Colitis
  • Continuous inflammation limited to the mucosa and submucosa.
  • Never extends beyond the ileocaecal valve.
• Crohn’s Disease
  • Patchy, transmural inflammation (involving all layers of the bowel wall).
  • Characterised by “skip lesions”, with normal areas between inflamed segments.

Symptoms

• Ulcerative Colitis
  • Bloody diarrhoea
  • Urgency and tenesmus
  • Mild abdominal pain, often in the left lower quadrant
• Crohn’s Disease
  • Non-bloody diarrhoea
  • Weight loss
  • Severe abdominal pain, often in the right lower quadrant

Endoscopy and Histology

• Ulcerative Colitis
  • Crypt abscesses
  • Goblet cell depletion
  • Granulomas are rare
• Crohn’s Disease
  • Cobblestone appearance due to deep ulcers and fissures
  • Skip lesions visible on endoscopy
  • Increased goblet cells
  • Non-caseating granulomas are more common

Barium Imaging

• Ulcerative Colitis (Barium enema)
  • “Drainpipe colon” – loss of haustration
  • Mucosal ulceration
• Crohn’s Disease (Small bowel enema)
  • Useful for examining the terminal ileum
  • Strictures – e.g. Kantor’s string sign
  • Fistulae
  • Proximal bowel dilation
  • “Rose thorn” ulcers

Relationship with Smoking

• Ulcerative Colitis
  • Smoking appears protective – associated with reduced disease severity
• Crohn’s Disease
  • Smoking worsens disease – associated with higher relapse rates and complications

Complications

• Ulcerative Colitis
  • Colorectal cancer, especially with extensive or long-standing disease
  • Toxic megacolon, which may lead to perforation
• Crohn’s Disease
  • Strictures and bowel obstruction due to transmural scarring
  • Fistulae and intra-abdominal abscesses are more common

Extra-Intestinal Manifestations

• Common to both:
  • Arthritis
  • Erythema nodosum
  • Pyoderma gangrenosum
• More common in Ulcerative Colitis:
  • Uveitis
  • Primary sclerosing cholangitis (PSC)

Surgical Interventions

• Ulcerative Colitis
  • Colectomy is curative as the disease is confined to the colon and rectum
• Crohn’s Disease
  • Surgery is not curative
  • Used to manage complications such as strictures, fistulae, and abscesses