Crohn’s disease — inflammatory bowel disease

Crohn’s disease is a chronic inflammatory condition of the digestive tract — one of two main types of inflammatory bowel disease (IBD), alongside ulcerative colitis. It affects roughly 1 in 350 people in the UK, often starting in teens or twenties, but can begin at any age.

Unlike colitis, Crohn’s inflammation can occur anywhere from mouth to anus — most commonly the terminal ileum (last part of small bowel) and colon — in patchy segments with healthy tissue between (“skip lesions”).

Symptoms

Varies by location and severity:

  • diarrhoea — may be bloody if colon involved
  • abdominal pain and cramping — often right lower abdomen
  • weight loss and reduced appetite
  • fatigue — from inflammation, anaemia, or poor sleep
  • mouth ulcers
  • perianal disease — fissures, fistulas, abscesses
  • joint pain, eye inflammation (uveitis), skin problems (erythema nodosum) — extra-intestinal manifestations

Flares — weeks to months of active symptoms — alternate with remission. Pattern is unpredictable.

Complications

  • strictures — scarring narrows bowel → cramping, bloating, obstruction risk
  • fistulas — abnormal tunnels between bowel and skin or other organs
  • abscesses
  • malabsorption — B12, iron, vitamin D, calcium deficiency
  • increased colon cancer risk if extensive colonic involvement — surveillance colonoscopy

Diagnosis

GP refers to gastroenterology. Investigations:

  • blood tests — inflammation (CRP, calprotectin), anaemia, nutrition
  • stool calprotectin — distinguishes IBD from irritable bowel syndrome
  • colonoscopy with biopsies — gold standard
  • MRI small bowel or capsule endoscopy — assesses small intestine

Diagnosis requires compatible history, examination, imaging, and histology — not made on symptoms alone.

Treatment — inducing and maintaining remission

Mild to moderate ileocolonic disease

  • Budesonide — steroid with limited systemic absorption
  • Aminosalicylates (mesalazine) — more effective in colonic than small bowel Crohn’s

Moderate to severe or steroid-dependent

  • Azathioprine / mercaptopurine — immunomodulators — require blood monitoring
  • Methotrexate
  • Biologics — anti-TNF (infliximab, adalimumab), ustekinumab, vedolizumab — for refractory disease

Severe flare

  • Hospital admission — IV steroids, fluids, nutrition
  • Surgery if obstruction, perforation, abscess, or failed medical therapy

Surgery

Not curative — removes diseased segment but recurrence common at anastomosis. Indications: strictures, fistulas, failed medicines, cancer surveillance findings.

Living with Crohn’s

  • stop smoking — doubles relapse risk; strongest modifiable factor
  • vaccinations — especially if on immunosuppressants (avoid live vaccines when immunocompromised)
  • screen for osteoporosis — steroids and inflammation affect bone
  • mental health support — chronic illness burden is significant
  • Crohn’s and Colitis UK — helpline, local groups, workplace rights

Crohn’s vs IBS

Irritable bowel syndrome causes similar symptoms but no structural inflammation — calprotectin normal, colonoscopy clear. IBS never causes bloody diarrhoea, weight loss, or night symptoms — red flags need IBD investigation.

Crohn’s is lifelong but manageable — early specialist care and modern medicines mean most people lead full working lives between flares.

Common questions about Crohn's disease

What is the difference between Crohn's disease and ulcerative colitis?
Both are inflammatory bowel disease (IBD). Crohn's can affect any part of the gut from mouth to anus with patchy full-thickness inflammation. Ulcerative colitis affects only the colon and rectum with continuous superficial inflammation. Crohn's more often causes fistulas, strictures, and malabsorption; colitis more often causes bloody diarrhoea confined to the large bowel.
What causes Crohn's disease?
Unknown — combination of genetic susceptibility, immune system dysregulation, gut microbiome changes, and environmental triggers (smoking is the clearest modifiable risk). Not caused by diet or stress alone, though both affect symptoms.
Is there a cure for Crohn's disease?
No cure currently — treatment aims for long remission. Some people have years between flares. Surgery removes damaged sections but Crohn's can recur elsewhere. New biologic medicines have transformed outcomes for moderate-to-severe disease.
What should I eat with Crohn's disease?
No single diet cures Crohn's. During flares, low-fibre or liquid diets may ease symptoms — dietitian guidance helps. Exclusive enteral nutrition (liquid formula diet) induces remission in some children and adults. Identify personal trigger foods in remission; ensure adequate calories, protein, iron, B12, and vitamin D.
Can stress cause a Crohn's flare?
Stress does not cause Crohn's but can trigger or worsen flares in some people. Gut-brain axis is real — psychological support and stress management are part of care.

Sources