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What is inflammatory bowel disease?

Inflammatory bowel disease (IBD) is a chronic (long-term) group of disorders characterized by inflammation in the digestive tract.1 In the United States alone, an estimated 1.5 million people currently suffer from IBD,2 with peak onset occurring in persons 15 to 30 years of age.3

There are two types of IBD: ulcerative colitis (UC) and Crohn’s disease (CD). The primary difference between these two types is the part of the digestive tract they affect. While UC impacts the colon and rectum, CD can affect any part of the gastrointestinal tract, though it is most common in the colon and terminal ileum.2 A second important difference between these two IBD types is that CD often is patchy with healthy areas in between the inflamed surfaces, while in UC the inflamed area forms one continuous stretch. Thirdly, the inflammation in CD affects multiple layers of the bowel wall, while UC affects only the surface layer of the gut.2

What are the symptoms?

The symptoms of IBD can vary depending on the location of inflammation and its severity.4 Symptoms may include:

  • Abdominal pain and cramping
  • Blood in your stool
  • Diarrhea
  • Fever and fatigue
  • Joint, skin, or eye problems
  • Reduced appetite and weight loss
  • Severe urge to have a bowel movement

IBD patients may have periods of active illness (known as “flares”) followed by periods of “remission” in which the symptoms decrease or even disappear. Patients can also experience extra-intestinal manifestations such as mouth sores or enteropathic arthritis, which 11% of patients with UC and 20% of patients with CD experience at some point during their lives.4

is an inflammatory disease affecting the joints and the area where ligaments and tendons attach to the bones. It occurs in patients with inflammatory bowel diseases (IBDs), gastrointestinal diseases such as Whipple’s disease (WD) and celiac disease (CD), and intestinal bypass surgery.17

 What are the causes?

Although the cause of IBD is unknown, it is believed to be a combination of interactions between genetic, environmental, and microbial factors, and the immune system’s response.5,6 Although both types of IBD – CD and UC – can appear in genetically susceptible individuals, heritability is less strongly associated with UC, meaning that CD occurs more often within families than UC.1,7

Environmental factors that can influence the severity of these diseases include lifestyle, diet, antibiotic use, and hygiene status.8 Patients with IBD have altered innate and acquired immune responses, so the immune system is unable to discriminate between healthy and unhealthy bacteria.9

Risk factors for developing IBD include7:

  • Age. Peak appearance of IBD is found in the second to fourth decade of life.
  • Blood in your stool.
  • Ethnicity. IBD risk is three times higher in Jewish populations than in non-Jewish.
  • Family history. Between 2-14% of CD patients and 8-14% UC patients have a relative with the condition.
  • Smoking. Smokers are twice as likely to develop CD.

How does this topic relate to my microbiome?

The presence of specific microorganisms within the human gut, and changes in the diversity and composition of gut bacteria, have been associated with both CD and UC.1,10 Though scientists are still researching whether microbial dysbiosis causes or is caused by mucosal inflammation,8,10 inflammation in IBD patients is generally characterized by a reduced diversity of microbiota, which could potentially increase susceptibility to pathogens.8 Some bacteria – like Escherichia coli, Salmonella, or Campylobacter – are associated with different forms of IBD.11 Moreover, infection by Clostridium difficile can trigger relapses.11

Which diseases/topics are related to inflammatory bowel disease?

IBD is a blanket term for a condition that affects the digestive tract and causes other conditions. Diseases that qualify as IBD include:

  • Crohn’s disease
  • Ulcerative colitis
  • Inflammatory bowel disease, unclassified

Additionally, persons with IBD may have12,13:

  • Anxiety
  • Arthritis
  • Depression
  • Osteoporosis
  • Primary sclerosing cholangitis
  • Renal stones
  • Secondary amyloidosis
  • Skin disorders
  • Venous and arterial thromboembolism
  • Vitamin B12 deficiency

Is a chronic liver disease, defined by a progressive obstruction of the normal flow of bile, associated with inflammation and fibrosis of the biliary ducts14.

Amyloidosis refers to a group of disease where an abnormal amount of protein accumulates in the body tissues. The term “secondary” is used to annotate that it is associated with an underlying other disease such as an inflammatory disease.15.

How can I take action?

First, consult your healthcare provider. IBD diagnosis is based on medical history, physical examinations, and imaging examinations. In order to diagnose IBD, a doctor might order an endoscopy or colonoscopy for an accurate diagnosis. During these procedures, a doctor will insert a long tube with a camera either through the mouth (endoscopy) or the rectum (colonoscopy) to take a look inside the intestinal tract. A healthy gut will look smooth and pink, while an inflamed gut will show red patches or areas, and may easily bleed.

Additional and complementary tests can be ordered, including:

  • Blood or stool tests
  • Imaging procedures

Once diagnosed, the activity, severity, and extent of IBD should be evaluated to adequately manage progression, remission, and intervention. Treatment may include medications, changes in lifestyle, probiotics, intervention treatments, and pain management.16,17,18


1. Kaser, A., Zeissig, S., & Blumberg, R. S. (2010). Inflammatory Bowel Disease. Annual Review of Immunology, 28(1), 573–621

2. Gajendran, M., Loganathan, P., Catinella, A. P., & Hashash, J. G. (2018). A comprehensive review and update on Crohn’s disease. Disease-a-Month, 64(2), 20–57

3. Loftus, E. V, & Sandborn, W. J. (2002). Epidemiology of inflammatory bowel disease. Gastroenterology Clinics of North America, 31(1), 1–20

4. Tontini, G. E., Vecchi, M., Pastorelli, L., Neurath, M. F., & Neumann, H. (2015). Differential diagnosis in inflammatory bowel disease colitis: State of the art and future perspectives. World Journal of Gastroenterology, 21(1), 21–46.

5. Zhang, Y.-Z. (2014). Inflammatory bowel disease: Pathogenesis. World Journal of Gastroenterology, 20(1), 91–9

6. Eisenstein, M. (2016). Biology: A slow-motion epidemic. Nature, 540(7634), S98–S99

7. Ordás, I., Eckmann, L., Talamini, M., Baumgart, D. C., & Sandborn, W. J. (2012). Ulcerative colitis. The Lancet, 380(9853), 1606–1619

8. Ananthakrishnan, et al. (2017). Environmental triggers in IBD: a review of progress and evidence. Nature Reviews Gastroenterology & Hepatology, 15(1), 39–49

9. Sartor, R. B. (2006). Mechanisms of Disease: pathogenesis of Crohn’s disease and ulcerative colitis. Nature Clinical Practice Gastroenterology & Hepatology, 3(7), 390–407

10. Ni, J., Wu, G. D., Albenberg, L., & Tomov, V. T. (2017). Gut microbiota and IBD: causation or correlation? Nature Reviews Gastroenterology & Hepatology, 14, 573

11. Ananthakrishnan, A. N. (2015). Epidemiology and risk factors for IBD. Nature Reviews Gastroenterology & Hepatology, 12(4), 205–217

12. Bähler, C., Schoepfer, A. M., Vavricka, S. R., Brüngger, B., & Reich, O. (2017). Chronic comorbidities associated with inflammatory bowel disease: prevalence and impact on healthcare costs in Switzerland. European Journal of Gastroenterology & Hepatology, 29(8), 916–925

13. López-San Román, A., & Muñoz, F. (2011). Comorbidity in inflammatory bowel disease. World Journal of Gastroenterology, 17(22), 2723–2733

14. Hirschfield, G. M., Karlsen, T. H., Lindor, K. D., & Adams, D. H. (2013). Primary sclerosing cholangitis. The Lancet, 382(9904), 1587–1599

15. Ebert, E. C., & Nagar, M. (2008). The American Journal of Gastroenterology, 103(3), 776–787

16. Matsuoka, K., et al. (2018). Evidence-based clinical practice guidelines for inflammatory bowel disease. Journal of Gastroenterology, 53(3), 305–353

17. Carter, M. J. (2004). Guidelines for the management of inflammatory bowel disease in adults. Gut, 53(suppl_5), v1–v16

18. Crohn’s & Colitis Foundation (2011). Diagnosing and Managing IBD