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What is inflammatory bowel disease (IBD)?

Image shows a human digestive system, labeled

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What is IBD?

Inflammatory bowel disease (IBD) is a term for two conditions (Crohn’s disease and ulcerative colitis) that are characterized by chronic inflammation of the gastrointestinal (GI) tract.1 Prolonged inflammation results in damage to the GI tract. Some of the differences between Crohn’s disease and ulcerative colitis:

Crohn’s Disease Ulcerative Colitis
Can affect any part of the GI tract (from the mouth to the anus)—Most often it affects the portion of the small intestine before the large intestine/colon. Occurs in the large intestine (colon) and the rectum
Image shows the human digestive system with areas affected by Crohn's Disease highlighted

click image to enlarge

Image shows the human digestive system with areas affected by Ulcerative Colitis highlighted

click image to enlarge

Damaged areas appear in patches that are next to areas of healthy tissue Damaged areas are continuous (not patchy) – usually starting at the rectum and spreading further into the colon
Inflammation may reach through the multiple layers of the walls of the GI tract Inflammation is present only in the innermost layer of the lining of the colon


What are the symptoms of IBD?

Some common symptoms are:

  • Persistent diarrhea
  • Abdominal pain
  • Rectal bleeding/bloody stools
  • Weight loss
  • Fatigue


What causes IBD?

The exact cause of IBD is unknown, but IBD is the result of a defective immune system. A properly functioning immune system attacks foreign organisms, such as viruses and bacteria, to protect the body. In IBD, the immune system responds incorrectly to environmental triggers, which causes inflammation of the gastrointestinal tract. There also appears to be a genetic component—someone with a family history of IBD is more likely to develop this inappropriate immune response.


How is IBD diagnosed?

IBD is diagnosed using a combination of endoscopy (for Crohn’s disease) or colonoscopy (for ulcerative colitis) and imaging studies, such as contrast radiography, magnetic resonance imaging (MRI), or computed tomography (CT). Physicians may also check stool samples to make sure symptoms are not being caused by an infection or run blood tests to help confirm the diagnosis.


How is IBD treated?

Several types of medications may be used to treat IBD: aminosalicylates, corticosteroids (such as prednisone), immunomodulators, and the newest class approved for IBD—the “biologics”. Several vaccinations for patients with IBD are recommended to prevent infections. Severe IBD may require surgery to remove damaged portions of the gastrointestinal tract, but advances in treatment with medications mean that surgery is less common than it was a few decades ago. Since Crohn’s disease and ulcerative colitis affect different parts of the GI tract, the surgical procedures are different for the two conditions.


IBD is not...

IBD is not Irritable Bowel Syndrome (IBS)…

IBD should not be confused with irritable bowel syndrome or IBS. Although people with IBS may experience some similar symptoms to IBD, IBD and IBS are very different. Irritable bowel syndrome is not caused by inflammation and the tissues of the bowel are not damaged the way they are in IBD. Treatment is also different. To learn more about the difference between inflammatory bowel disease and irritable bowel syndrome, go to

IBD is not celiac disease…

Celiac disease is another condition with similar symptoms to IBD. It is also characterized by inflammation of the intestines. However, the cause of celiac disease is known and is very specific. It is an inflammatory response to gluten (a group of proteins found in wheat and similar grains). The symptoms of celiac disease will go away after starting a gluten-free diet, although it usually will be months before the full effects of the new diet will be reached.



  1. The Facts About Inflammatory Bowel Diseases. New York, NY: Crohn’s and Colitis Foundation of America; 2014. [PDF-2.32MB].