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Bowel Inflammation and Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a form of chronic, inflammatory arthritis that primarily affects the spine, although joints in the arms and legs can also be affected. The chronic inflammation can also cause extra-articular (beyond the joint) manifestations, including inflammation in the bowel, or gut.

People with AS have an increased risk of developing inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn’s disease. It is estimated that between 5% and 10% of people with AS have IBD. In addition, a much larger percentage of people with AS experience gut inflammation, which may also cause intestinal symptoms.1

What are the symptoms of bowel inflammation?

If someone is experiencing bowel inflammation, they may have symptoms such as2:

These symptoms may change over time and may range from mild to severe. Any of these symptoms should be reported to and evaluated by a healthcare professional.

How is the microbiome impacted in people with ankylosing spondylitis?

The microbiome is the collection of microorganisms like bacteria and fungi that normally live in the human body. The microbiome of the gut has been proven to have multiple benefits to the health of the individual, including synthesizing vitamins, assisting in digesting foods, supporting the functioning of the immune system, and regulating mood. A healthy microbiome is one that is diverse and balanced in the types of microorganisms.3

If the microbiome becomes unbalanced, such as when certain strains of bacteria are missing or certain strains becoming overly populated, it can cause disruptions in the individual’s health. An imbalance of the microbiome has been associated with inflammatory bowel disease, irritable bowel syndrome, obesity, type 2 diabetes, and allergies.3 Researchers have found that the gut microbiome is altered in people with AS, and this imbalance in the microbiome may be actively involved in the disease process of AS.4

Is there a genetic connection between AS and IBD?

AS and IBD seem to share similar genetic mutations, and both diseases tend to run in families. Just as people with AS have a higher risk of developing IBD, people with IBD also have a higher risk of developing AS.5,6

How is bowel inflammation assessed?

If someone is experiencing intestinal or digestive symptoms, they need to be seen by a doctor. While many people start with a primary care physician, it may be necessary to see a gastroenterologist, a specialist in stomach and intestinal disease. Diagnosing intestinal issues may involve a number of tests, including a physical exam and symptom history, blood tests, a stool test, a colonoscopy, and imaging tests like x-rays.5,7

Written by: Emily Downward | Last reviewed: February 2019
  1. Rudwaleit M, Baeten D. Ankylosing spondylitis and bowel disease. Best Pract Res Clin Rheumatol. 2006 Jun;20(3):451-71. doi: 10.1016/j.berh.2006.03.010. Abstract.
  2. The Facts About Inflammatory Bowel Diseases. Crohn's & Colitis Foundation of America. Available at Published November 2014. Accessed 2/1/19.
  3. Bull MJ, Plummer NT. Part 1: The Human Gut Microbiome in Health and Disease. Integr Med (Encinitas). 2014;13(6):17-22.
  4. Ciccia F, Rizzo A, Triolo G. Subclinical gut inflammation in ankylosing spondylitis. Curr Opin in Rheum. 2016 Jan;28(1):89-96. doi: 10.1097/BOR.0000000000000239. Abstract.
  5. Arthritis. Crohn's and Colitis Foundation. Available at Accessed 2/1/19.
  6. GI Joint. Spondylitis Association of America. Available at Accessed 2/1/19.
  7. Diagnosing and managing IBD. Crohn's & Colitis Foundation of America. Available at Accessed 2/1/19.