Overview
Inflammatory bowel disease is a term covering two chronic conditions: Crohn's disease and ulcerative colitis. Both cause persistent inflammation of the digestive tract. Ulcerative colitis affects the colon and rectum; Crohn's disease can affect any part of the gastrointestinal tract from mouth to anus. Both involve flares and remissions and require long-term management.
How common is it?
IBD affects approximately 300,000 people in the UK. Crohn's disease and ulcerative colitis have similar prevalence. Diagnosis most commonly occurs between age 15 and 35, though it can present at any age.
Causes and risk factors
IBD results from an abnormal immune response to gut bacteria in genetically susceptible individuals, triggered by environmental factors.
Common risk factors
- Genetic susceptibility (over 200 genetic variants identified, including NOD2)
- Dysregulated immune response to intestinal microbiome
- Smoking (increases Crohn's risk; paradoxically protective in ulcerative colitis)
- Antibiotic use in early life
- Western diet, high in processed foods and low in fibre
- Urban living and hygiene hypothesis
- Appendectomy (reduces UC risk)
- Stress (triggers flares rather than causing the condition)
Symptoms
- Persistent diarrhoea, often with blood or mucus
- Abdominal pain and cramping
- Urgency and frequency to open bowels
- Fatigue
- Unintentional weight loss
- Fever during flares
- Anaemia from chronic blood loss
- Crohn's: perianal disease, fistulae, mouth ulcers
- Extra-intestinal: joint pain, eye inflammation, skin rashes (erythema nodosum)
When to see a doctor
See a doctor for persistent change in bowel habit, blood in stools, or unexplained weight loss. These symptoms require investigation to exclude IBD and bowel cancer. Severe flares with bloody diarrhoea more than 6 times daily, fever, and abdominal pain may require hospital admission.
Diagnosis
Colonoscopy with biopsies is the key diagnostic investigation. Faecal calprotectin is a non-invasive marker of intestinal inflammation. MRI small bowel for Crohn's extent. Blood tests assess inflammation, anaemia, and nutritional deficiencies.
Treatments
5-ASA drugs (mesalazine)
First-line for mild to moderate ulcerative colitis. Given orally and/or rectally. Maintain remission effectively with long-term use. Less effective in Crohn's disease.
Corticosteroids
Prednisolone or budesonide used to induce remission during flares. Not suitable for long-term use due to side effects. Intravenous steroids for severe flares.
Immunomodulators
Azathioprine, 6-mercaptopurine, or methotrexate used for maintenance of remission. Take 3 months to reach full effect. Regular blood monitoring required.
Biologics and small molecules
Anti-TNF agents (infliximab, adalimumab), vedolizumab, ustekinumab, and JAK inhibitors (tofacitinib, upadacitinib) for moderate to severe IBD not responding to conventional therapy. Highly effective at inducing and maintaining remission.
Surgery
Colectomy can cure ulcerative colitis. For Crohn's, surgery removes the most severely diseased segments but is not curative. Around 50 to 80% of Crohn's patients need surgery within 20 years of diagnosis.
Self-care and lifestyle
- Work with a dietitian to identify and manage dietary triggers
- Maintain adequate vitamin D, B12, folate, and iron (commonly deficient in IBD)
- Do not stop medication during remission without specialist advice
- Flu and pneumococcal vaccination is important as immunosuppressants increase infection risk
Prevention
IBD cannot currently be prevented. Breastfeeding, diverse diet, and avoiding unnecessary antibiotics in childhood may reduce risk.