| Factor | Crohn’s Disease | Ulcerative Colitis |
| Distribution | Affects small bowel and large bowel | Affects large bowel only |
| Endoscopy findings | Rectum frequently spared Inflammation not continuous (presence of skip lesions) Bowel wall is thickened and has a ‘cobblestoned’ appearance due to deep ulcers and swelling of the tissue | Rectum always affected Inflammation is uniform Bowel wall is thin with loss of vascular pattern (blood vessels not visible) |
| Radiology | Strictures are common Deep fissures and fistulae are common Asymmetrical inflammation | Strictures and fissures are much less common in UC Symmetrical inflammation |
| Histology | Presence of granulomas are almost diagnostic Inflammation extends through the mucosa and muscle of the bowel The increase in white cells tend to be lymphocytes | Granulomata absent Inflammation usually confined to mucosa The increase in white cells tend to be polymorphs |
| Diet | Remission achieved with enteral feed followed by exclusion/ elimination diet | Unaffected by diet |
| Clinical appearance | Patients often thin and may be malnourished due to intestinal malabsorption of nutrients Diarrhoea – only sometimes with blood Abdominal mass common | Weight loss usually related to the severity of active disease Bloody diarrhoea Abdominal mass uncommon |
| Smoking | Strongly associated with smoking Predicts a worse course of disease Increases risk of surgery & further surgery | Associated with non-smokers or ex-smokers Appears to protect against disease |