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24th July 2023
Crohn’s disease and ulcerative colitis
Crohn’s disease and ulcerative colitis are coined under the umbrella term of Inflammatory Bowel Disease (IBD). They have many similarities, which can make differentiating them difficult. Some of the key differences used to distinguish the two conditions are summarised in the table below.
| Crohn’s disease | Ulcerative colitis | |
|---|---|---|
| Demographic | Peak incidence 20-29 years old | Peak incidence 15-25 years old |
| Risk factors | Smoking (3-4x increased risk), genetic predisposition (15-20% of patients usually have an affected family member, a high degree of concordance is observed in identical twins) | Family history
Non-smoker |
| Pathophysiology | Affects any part of the GI tract (Approximately 80% of patients demonstrate small bowel involvement, particularly in the distal ileum)
Non-continuous lesions (i.e. skip lesions) Inflammation affects every layer of the bowel, i.e. transmural (therefore can lead to stricturing/fistulae) |
Begins at the rectum and spreads proximally
Only affects large bowel Continuous disease Inflammation is restricted to the submucosa |
| Clinical features | Abdominal pain
Diarrhoea (usually watery and non-bloody) Weight loss Fatigue Perianal disease – perianal pain, fever, purulent discharge Oral ulcers |
Bloody diarrhoea
Abdominal pain Urgency Tenesmus |
| Extra-intestinal manifestations | Arthritis (generally large joint)
Ocular involvement (uveitis, iritis and episcleritis) Dermatological conditions (erythema nodosum, pyoderma gangrenosum, aphthous lesions) Renal calculi (calcium oxalate stones) Osteoporosis (due to impaired vitamin D and calcium absorption, and corticosteroid usage) |
Primary sclerosing cholangitis
Erythema nodosum Episcleritis Uveitis Metabolic bone disease Arthritis |
| Complications/associated conditions | Strictures (which can lead to bowel obstruction)
Fistulae (enteroenteric/enterovaginal/enterocutaneous) |
Strictures (which can lead to bowel obstruction)
Colorectal cancer Toxic megacolon |
Table 1: Key differences between Crohn’s disease and ulcerative colitis
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