Overview
Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are chronic gastrointestinal conditions with overlapping symptoms but distinct underlying causes and diagnostic approaches.
IBS is a functional gastrointestinal disorder characterized by abdominal pain, bloating and changes in bowel habits (diarrhea, constipation or both), with no detectable structural abnormalities or inflammation. It is considered a disorder of gut-brain interaction.1
IBD refers to a group of inflammatory conditions, primarily Crohn’s disease and ulcerative colitis, that involve chronic inflammation of the gastrointestinal tract and can lead to intestinal damage. Unlike IBS, IBD is visible through endoscopic and histologic evaluation.2,5
Understanding the difference between IBS and IBD is crucial for appropriate diagnosis, treatment and patient care.1,3
| Condition | Inflammatory Bowel Disease (IDB) | Irritable Bowel Syndrome (IBS) |
| Basic etiology | Autoimmune-driven chronic inflammation 2 | Disorder of gut-brain axis 1 |
IBS is not associated with an infectious cause, although some cases may follow a gastrointestinal infection (post-infectious IBS).3
IBD is thought to result from a complex interaction of genetics, immune dysregulation, environmental triggers and gut microbe – though it is not directly transmissible between individuals.2,3
There is no known method to entirely prevent either condition, but risk reduction and symptom management are possible:
- IBS – Identifying and avoiding personal symptom triggers (e.g., stress, certain foods), maintaining regular eating and sleeping habits, and addressing psychological stress can reduce symptom flare-ups.3,4
- IBD – While the exact cause is unknown, lifestyle factors such as smoking cessation, diet modification, and early intervention in at-risk individuals may reduce severity or frequency of flares.2,5
Diagnosis: In vitro diagnostic (IVD) tools are essential in differentiating IBS from IBD, as the conditions often present with similar symptoms. Key diagnostic steps include:
IBS
- Diagnosis based on Rome IV criteria (symptom-based)1
- Exclusion of organic disease via normal inflammatory markers and imaging3
- IVD tests may include:
- Fecal calprotectin or lactoferrin (to rule out IBD)3,4
- Celiac serology to exclude celiac disease3
IBD
- Diagnosis based on clinical, endoscopic, histologic and radiologic findings2,5
- IVD tests play a critical role:
- Fecal calprotectin – elevated in active IBD3,5
- CRP/ESR – systemic inflammation markers5
- Genetic and serologic markers (e.g., pANCA, ASCA) may support diagnosis5
- Stool culture – to rule out infectious mimics3
Treatment: A combination of dietary, lifestyle and pharmacologic therapies is often used in combination to reduce the symptoms of IBS and IBD, including:
IBS
- Lifestyle and dietary changes (e.g., low FODMAP diet)4
- Pharmacologic therapy: antispasmodics, laxatives, antidiarrheals, or neuromodulators1,4
- Psychological therapy (e.g., CBT or gut-directed hypnotherapy)4
IBD
- Anti-inflammatory agents (e.g., 5-ASA), corticosteroids, immunomodulators and biologics2,5
- Nutritional support and, in some cases, surgical intervention2
- Long-term monitoring with IVD and endoscopic tools to assess disease activity and guide therapy5
- Lacy, B. E., Mearin, F., Chang, L., et al. (2016). Bowel disorders. Gastroenterology, 150(6), 1393–1407.e5. https://doi.org/10.1053/j.gastro.2016.02.031
- Torres, J., Mehandru, S., Colombel, J. F., & Peyrin-Biroulet, L. (2017). Crohn’s disease. The Lancet, 389(10080), 1741–1755. https://doi.org/10.1016/S0140-6736(16)31711-1
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (2023). IBS and IBD Information. https://www.niddk.nih.gov/health-information/digestive-diseases/irritable-bowel-syndrome
- Chey, W. D., & Keefer, L. (2021). Behavioral and diet therapies in IBS. Gastroenterology Clinics, 50(3), 527–545. https://doi.org/10.1016/j.gtc.2021.05.009
- Rubin, D. T., Ananthakrishnan, A. N., Siegel, C. A., Sauer, B. G., & Long, M. D. (2019). ACG Clinical Guideline: Ulcerative Colitis in Adults. American Journal of Gastroenterology, 114(3), 384–413. https://doi.org/10.14309/ajg.0000000000000152
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