Understanding Inflammatory Bowel Disease (IBD)
Inflammatory Bowel Disease (IBD) is an umbrella term for conditions that cause chronic inflammation of the gastrointestinal tract.
Crohn’s disease and ulcerative colitis are the two most common types of IBD [1]. Other recognised forms include:
- microscopic colitis: inflammation visible only under a microscope, with a normal-appearing colon on endoscopy
- indeterminate colitis: used when features of both Crohn's disease and ulcerative colitis are present and a definitive diagnosis cannot be made
Some conditions (such as Behçet’s disease) can cause intestinal symptoms that closely mimic IBD but are classified as separate conditions by mainstream medicine.
These conditions are characterised by periods of active disease (flares) and periods of remission (when symptoms are reduced or absent).
What is Crohn’s Disease?
Crohn’s disease is a type of IBD that can affect any part of the gastrointestinal tract from the mouth to the anus, but most commonly affects the end of the small intestine (ileum) and the beginning of the colon. In Crohn’s disease:
- Inflammation may extend through all layers of the bowel wall [2]
- Affected areas may be patchy, with healthy sections in between (known as "skip lesions")
- Common symptoms include abdominal pain, diarrhoea, fatigue, weight loss, and malnutrition
- Complications can include strictures (narrowing of the intestine), fistulas (abnormal connections between organs), and abscesses [3]
What is Ulcerative Colitis?
Ulcerative colitis is a type of IBD that affects only the colon (large intestine) and rectum. In ulcerative colitis:
- Inflammation is typically limited to the innermost lining of the colon [4]
- The inflammation is continuous, starting from the rectum and potentially extending throughout the colon
- Common symptoms include bloody diarrhoea, abdominal cramping, urgency to defecate, and fatigue
- Complications can include severe bleeding, toxic megacolon, and increased risk of colorectal cancer [5]
How Are They Related?
Both Crohn’s disease and ulcerative colitis:
- Are chronic inflammatory conditions of the digestive tract
- Have similar symptoms and can significantly impact quality of life
- Are believed to result from an abnormal immune response to environmental triggers in genetically susceptible individuals [6]
- Have no known cure, but treatments can help manage symptoms and achieve remission
- Often appear in young adults between the ages of 15 and 35, though they can develop at any age [7]
How Do They Differ?
Despite their similarities, there are important differences between Crohn’s disease and ulcerative colitis:
| Feature | Crohn's Disease | Ulcerative Colitis |
|---|---|---|
| Location | Can affect any part of the GI tract | Limited to the colon and rectum |
| Pattern | Patchy inflammation with skip lesions | Continuous inflammation |
| Depth | Can affect all layers of the bowel wall | Typically affects only the innermost lining |
| Complications | Strictures, fistulas, abscesses | Severe bleeding, toxic megacolon |
| Surgical outcomes | Surgery may induce remission, but not cure the disease | Total colectomy can "cure" ulcerative colitis |
Diagnosis
Diagnosing IBD usually requires an endoscopic procedure, which also helps distinguish Crohn’s disease from ulcerative colitis. Reaching a diagnosis may involve a combination of:
- Medical history and physical examination
- Blood tests to check for anaemia, inflammation markers, and antibodies
- Stool tests to rule out infections and check for inflammation
- Imaging studies such as computed tomography (CT) scans, magnetic resonance imaging (MRI), and intestinal ultrasound (IUS) [8]
- Endoscopic procedures (colonoscopy and/or upper endoscopy)
Treatment
Treatment approaches for both conditions may include:
- Anti-inflammatory medications (e.g. aminosalicylates, corticosteroids)
- Immunosuppressants
- Biologic therapies (e.g. TNF inhibitors, integrin inhibitors, interleukin inhibitors)
- Small molecule drugs (e.g. JAK inhibitors)
- Antibiotics
- Surgery [9]
Living with IBD
IBD is a lifelong condition, but it doesn’t have to define your life. With the right management, many people with Crohn’s disease or ulcerative colitis lead full, active lives. Working closely with your healthcare team, looking after your general health, and leaning on support groups can all make the condition easier to live with. [10]
Extraintestinal Manifestations
IBD can cause inflammation and symptoms beyond the digestive tract, known as extraintestinal manifestations (EIMs). A systematic review and meta-analysis of 52 studies involving over 352,000 patients found that approximately 24% of all people with IBD experience at least one joint, skin, or eye EIM, rising to 35% in Crohn’s disease and 27% in ulcerative colitis. [11]
EIMs can affect several parts of the body. The main sites include:
- Joints: peripheral arthritis (affecting limb joints) and axial disease (sacroiliitis, ankylosing spondylitis) are the most frequent EIMs
- Skin: erythema nodosum (tender red nodules, typically on the shins) and pyoderma gangrenosum (deep, painful skin ulcers)
- Eyes: uveitis and episcleritis, which can cause eye pain, redness, and blurred vision
- Liver and bile ducts: primary sclerosing cholangitis (PSC), which occurs more commonly in ulcerative colitis
EIMs may appear before, during, or independently of intestinal disease activity and often require specialist management alongside gastroenterological care.
Recommended Reading
If you’d like to read more about the topics above, these resources explain IBD in plain, everyday language. They’re written for patients and families rather than clinicians, and the information applies wherever you live.
Understanding your condition
- MedlinePlus, from the US National Library of Medicine, offers clear, ad-free overviews of Crohn's disease and ulcerative colitis, with links to trusted further reading.
- Mayo Clinic has easy-to-read guides to Crohn's disease and ulcerative colitis, plus a side-by-side comparison of the two conditions.
Living with IBD and finding support
- World IBD Day is a global awareness day (19 May) run by patient organisations in more than 50 countries, with personal stories and support for the millions of people living with IBD worldwide.
- IBD Passport gives practical, patient-focused advice on everyday life and travelling with IBD, useful wherever you live.
References
- Kaplan GG. The global burden of IBD: from 2015 to 2025. Nat Rev Gastroenterol Hepatol. 2015;12(12):720-727. doi:10.1038/nrgastro.2015.150
- Baumgart DC, Sandborn WJ. Crohn's disease. Lancet. 2012;380(9853):1590-1605. doi:10.1016/S0140-6736(12)60026-9
- Torres J, Mehandru S, Colombel JF, Peyrin-Biroulet L. Crohn's disease. Lancet. 2017;389(10080):1741-1755. doi:10.1016/S0140-6736(16)31711-1
- Ungaro R, Mehandru S, Allen PB, Peyrin-Biroulet L, Colombel JF. Ulcerative colitis. Lancet. 2017;389(10080):1756-1770. doi:10.1016/S0140-6736(16)32126-2
- Danese S, Fiocchi C. Ulcerative colitis. N Engl J Med. 2011;365(18):1713-1725. doi:10.1056/NEJMra1102942
- Khor B, Gardet A, Xavier RJ. Genetics and pathogenesis of inflammatory bowel disease. Nature. 2011;474(7351):307-317. doi:10.1038/nature10209
- Molodecky NA, Soon IS, Rabi DM, et al. Increasing incidence and prevalence of the inflammatory bowel diseases with time, based on systematic review. Gastroenterology. 2012;142(1):46-54.e42. doi:10.1053/j.gastro.2011.10.001
- Maaser C, Sturm A, Vavricka SR, et al. ECCO-ESGAR Guideline for Diagnostic Assessment in IBD Part 1: Initial diagnosis, monitoring of known IBD, detection of complications. J Crohns Colitis. 2019;13(2):144-164. doi:10.1093/ecco-jcc/jjy113
- Torres J, Bonovas S, Doherty G, et al. ECCO Guidelines on Therapeutics in Crohn's Disease: Medical Treatment. J Crohns Colitis. 2020;14(1):4-22. doi:10.1093/ecco-jcc/jjz180
- Kemp K, Dibley L, Chauhan U, et al. Second N-ECCO Consensus Statements on the European Nursing Roles in Caring for Patients with Crohn's Disease or Ulcerative Colitis. J Crohns Colitis. 2018;12(7):760-776. doi:10.1093/ecco-jcc/jjy020
- Kilic Y, Kamal S, Jaffar F, Sriranganathan D, Quraishi MN, Segal JP. Prevalence of Extraintestinal Manifestations in Inflammatory Bowel Disease: A Systematic Review and Meta-analysis. Inflamm Bowel Dis. 2024;30(2):230-239. doi:10.1093/ibd/izad061
Global Resources
For additional resources available worldwide, please visit our Global Resources page.