Inflammatory bowel disease (IBD) is a term for two conditions — Crohn’s disease and ulcerative colitis (UC) — that cause chronic inflammation of the digestive tract. The UK has one of the highest rates of IBD in the world, with around 500,000 people affected. Both conditions are lifelong but manageable with the right treatment, and many people live full, active lives.
Crohn’s Disease vs Ulcerative Colitis: Key Differences
| Feature | Crohn’s Disease | Ulcerative Colitis |
|---|---|---|
| Location | Anywhere from mouth to anus; most commonly terminal ileum and colon | Colon and rectum only |
| Pattern of inflammation | Patchy (“skip lesions”), transmural (full thickness of bowel wall) | Continuous, from rectum upwards; mucosa only |
| Common symptoms | Abdominal pain, diarrhoea, weight loss, fatigue | Bloody diarrhoea, urgency, cramping |
| Perianal disease | Common (fistulas, abscesses) | Rare |
| Surgery | Does not cure; may need multiple procedures | Colectomy can be curative |
| Diagnosis peak age | 15–30 and 60–80 | 15–25 and 55–65 |
Symptoms of Crohn’s Disease
- Persistent diarrhoea (may contain blood or mucus)
- Abdominal cramping and pain, often in the lower right or around the navel
- Unintended weight loss
- Extreme fatigue
- Nausea and vomiting
- Mouth ulcers (aphthous ulcers)
- Perianal symptoms — fissures, fistulas, abscesses
- Fever during flares
- Reduced appetite
Symptoms of Ulcerative Colitis
- Bloody diarrhoea — the hallmark symptom
- Urgency to open bowels; sometimes unable to hold on
- Cramping and pain in the lower abdomen
- Passing mucus with stools
- Fatigue and anaemia
- Weight loss during flares
- In severe cases: fever, rapid heart rate, abdominal tenderness
Extra-Intestinal Manifestations
IBD can affect organs beyond the gut. These “extra-intestinal” features affect up to 40% of people with IBD:
- Joints — Arthritis, sacroiliitis (lower back pain), ankylosing spondylitis
- Eyes — Uveitis, episcleritis (red, painful eyes)
- Skin — Erythema nodosum (tender red nodules), pyoderma gangrenosum
- Liver — Primary sclerosing cholangitis (PSC), more common in UC
- Bones — Osteoporosis (from malabsorption and steroid use)
- Anaemia — Iron deficiency and anaemia of chronic disease
Causes and Risk Factors
The exact cause of IBD is unknown, but it results from an abnormal immune response to the gut microbiome in genetically susceptible individuals. Contributing factors include:
- Genetics — Having a first-degree relative with IBD increases risk 10-fold; over 200 genetic variants identified
- Immune dysfunction — The immune system mistakenly attacks harmless gut bacteria
- Gut microbiome imbalance — Reduced microbial diversity associated with IBD
- Smoking — Significantly increases Crohn’s disease risk; paradoxically, smoking may mildly protect against UC
- NSAIDs and antibiotics — May trigger or worsen IBD flares
- Westernised diet — High fat, low fibre diet linked to higher rates
- Appendectomy — Reduces risk of UC
Diagnosis
Diagnosis of IBD involves:
- Blood tests — FBC (anaemia), CRP/ESR (inflammation markers), albumin, LFTs, B12, folate, ferritin
- Stool tests — Faecal calprotectin (a marker of intestinal inflammation; elevated in IBD, helps distinguish from IBS); stool cultures to exclude infection
- Colonoscopy with biopsies — Gold standard for diagnosis; can visualise the mucosa and take tissue samples
- MRI enterography — Images the small bowel in Crohn’s disease; also used to assess perianal disease
- CT scan — For complications (abscess, perforation, obstruction)
- Capsule endoscopy — Swallowable camera for small bowel Crohn’s
IBD vs IBS: How to Tell the Difference
IBD and IBS have overlapping symptoms but are very different conditions. IBD involves visible inflammation and carries risks of complications, whereas IBS does not cause physical damage to the bowel.
| Feature | IBD | IBS |
|---|---|---|
| Blood in stools | Common | No |
| Raised inflammatory markers (CRP) | Yes | No |
| Faecal calprotectin | Elevated (>250 μg/g) | Normal (<50 μg/g) |
| Weight loss | Common | Rare |
| Colonoscopy findings | Visible inflammation | Normal |
| Waking at night with symptoms | Common | Unusual |
Treatment: Crohn’s Disease
Inducing Remission
- Exclusive enteral nutrition (EEN) — First-line for children; liquid diet formula for 6–8 weeks. Adults may also use partial enteral nutrition.
- Corticosteroids — Prednisolone or budesonide (Entocort); used for active flares, not for long-term maintenance due to side effects
- Biologics — Infliximab (Remicade, Inflectra) or adalimumab (Humira) for moderate-to-severe or steroid-refractory disease; NICE-approved on NHS
Maintaining Remission
- Azathioprine or mercaptopurine — Immunosuppressants; TPMT testing done before starting
- Methotrexate — Alternative immunosuppressant
- Biologic agents — Adalimumab, infliximab, vedolizumab (Entyvio), ustekinumab (Stelara); all available on NHS for appropriate indications
- Small molecule drugs — Upadacitinib (Rinvoq); JAK inhibitor approved for Crohn’s by NICE
Treatment: Ulcerative Colitis
Mild-to-Moderate UC
- Aminosalicylates (5-ASAs) — Mesalazine (Asacol, Octasa, Pentasa) or sulfasalazine; first-line for mild-moderate UC; available as tablets, suppositories, enemas
- Topical steroids — Suppositories or enemas for proctitis (rectal-only disease)
Moderate-to-Severe UC
- Oral corticosteroids — Prednisolone for acute flares
- Immunosuppressants — Azathioprine, mercaptopurine
- Biologics — Infliximab, adalimumab, vedolizumab, golimumab (Simponi); NICE-approved for moderate-severe UC
- JAK inhibitors — Tofacitinib (Xeljanz), filgotinib (Jyseleca), upadacitinib (Rinvoq); for adults with moderate-severe UC
Surgery for UC
Around 1 in 5 people with UC will eventually need surgery. Removal of the entire colon (colectomy) is curative. The preferred procedure is an ileo-anal pouch anastomosis (IPAA / J-pouch), which avoids a permanent stoma in most cases.
Diet and Lifestyle
- There is no single “IBD diet” — dietary triggers vary greatly between individuals
- During flares, a low-residue diet may reduce symptoms (avoiding high-fibre foods, wholegrains, raw vegetables)
- Vitamin D and B12 supplementation are commonly needed, especially in Crohn’s
- Alcohol and smoking (for Crohn’s) worsen disease activity and should be minimised/stopped
- Keeping a food and symptom diary can help identify personal triggers
- Registered dietitian referral is recommended for all IBD patients with nutritional concerns
Cancer Risk in IBD
Long-standing IBD affecting the colon increases the risk of colorectal cancer. The NHS offers surveillance colonoscopies every 1–5 years (depending on risk) to people who have had extensive colitis for 8 or more years. Compliance with surveillance is important for early detection.
NHS Support and Resources
- Crohn’s & Colitis UK — crohnsandcolitis.org.uk — Helpline: 0300 222 5700
- Guts UK — gutscharity.org.uk — Digestive health charity
- NHS IBD information — nhs.uk/conditions/crohns-disease and nhs.uk/conditions/ulcerative-colitis
- IBD UK — ibduk.org — National coalition for IBD services
This article provides general information about IBD. It is not a substitute for medical advice from your gastroenterologist or IBD team.
Related Health Guides on YourHealthXpert
Explore these related NHS-aligned health guides:
- IBS Guide — Crohn’s disease and IBS are frequently confused; understand the key diagnostic differences and why accurate diagnosis matters.
- Coeliac Disease Guide — Both Crohn’s and coeliac are autoimmune digestive conditions; learn how NHS gastroenterologists differentiate between them.
- Bowel Cancer Guide — Long-standing Crohn’s colitis increases bowel cancer risk; understand the NHS surveillance colonoscopy programme.
- Osteoporosis Guide — Crohn’s disease causes malabsorption and steroid use increases osteoporosis risk significantly; learn about NHS bone protection strategies.
- Rheumatoid Arthritis Guide — Joint inflammation is a common extra-intestinal feature of Crohn’s; understand the NHS approach to managing IBD-related arthropathy.
- Liver Disease Guide — Liver complications including primary sclerosing cholangitis (PSC) can occur with IBD; understand the connection and NHS monitoring.