What Is Crohn's Disease?
Crohn's disease is a chronic inflammatory bowel disease that can affect any part of the digestive tract from mouth to anus, though it most commonly affects the terminal ileum (end of the small intestine). Unlike UC, the inflammation is patchy and can penetrate the full thickness of the bowel wall.
Symptoms
- Persistent diarrhoea (often without blood, unlike UC)
- Abdominal pain and cramping — classically in the right lower abdomen
- Weight loss and malnutrition from malabsorption
- Fatigue and fever during flares
- Mouth ulcers (aphthous ulcers)
- Perianal disease: fistulas, abscesses, skin tags
Extraintestinal Manifestations
- Joint pain (arthritis)
- Skin rashes (erythema nodosum, pyoderma gangrenosum)
- Eye inflammation (uveitis, episcleritis)
- Primary sclerosing cholangitis (liver)
Diagnostic Tests
| Test | Finding |
|---|---|
| Faecal calprotectin | Elevated — confirms gut inflammation |
| CRP & ESR | Elevated in active disease |
| Full Blood Count | Anaemia, raised WBC |
| Iron, B12, folate, vitamin D | Malabsorption — especially B12 in ileal disease |
| Colonoscopy + ileoscopy + biopsy | Skip lesions, cobblestone mucosa, granulomas |
| MRI enterography | Small bowel Crohn's — strictures, fistulas |
FAQs
Why does Crohn's cause B12 deficiency?
The terminal ileum is where B12 is absorbed. When Crohn's affects this area — or after surgical removal — B12 absorption is impaired.
Can Crohn's be cured?
There is no cure. Surgery may remove affected bowel but Crohn's often recurs near the anastomosis (join). Treatment focuses on inducing and maintaining remission.
What is the difference between Crohn's and UC blood tests?
Both show elevated CRP, calprotectin and anaemia. B12 and vitamin deficiencies are more specific to Crohn's small bowel involvement.
Medical Disclaimer: Crohn's disease requires long-term specialist management. Nutritional deficiencies need regular monitoring and supplementation.