Inflammatory Bowel Disease and Ankylosing Spondylitis

Last updated: June 2019

People with ankylosing spondylitis (AS) have an increased risk of developing inflammatory bowel disease. Inflammatory bowel disease (IBD) is a term used to describe several conditions that involve chronic inflammation of the digestive tract, including ulcerative colitis and Crohn's disease.

How are AS and inflammatory bowel disease linked?

Researchers have uncovered common inflammatory pathways in both AS and IBD that can cause inflammation in both the gut and the joints.1 In some people, IBD develops before AS. In others, AS develops before IBD.

What are the different types of inflammatory bowel disease?

The term IBD encompasses several conditions, including Crohn's disease, ulcerative colitis, and indeterminate colitis. Although inflammation of the digestive tract is present in each condition, there are some key differences among them, such as where and how they affect the digestive tract.2,3

Crohn's disease can affect any part of the digestive tract. This includes the oral cavity, esophagus, liver, stomach, small intestine, large intestine, and rectum, all of which are critical structures in the digestion and nutrient absorption process. Ulcerative colitis, on the other hand, affects only the rectum (anus) and the large intestine (colon). The inflammation pattern in Crohn's disease is patchy in nature and encompasses the entire thickness of the intestinal or colon wall. In ulcerative colitis, the inflammation pattern is continuous and only affects the innermost layer of the intestinal wall. In certain cases, it may be difficult to distinguish between these conditions, and an individual may be diagnosed with indeterminate colitis.2-4

How common is inflammatory bowel disease in people with AS?

It is estimated that between 5% and 10% of people with AS have IBD.1 When looking at people with IBD, approximately 2-3% of them have AS, and it is more common among people with Crohn's disease than ulcerative colitis.5

How is inflammatory bowel disease diagnosed?

If someone is experiencing symptoms of IBD, such as abdominal pain, persistent diarrhea, blood in the stool, unexpected weight loss, reduced appetite, and fatigue, they may be given a scope examination of the digestive tract. This scope involves inserting a long, thin tube with a camera and light attached into the body, either through the mouth (upper endoscopy) or through the rectum (colonoscopy), or sometimes both. During the scope, a biopsy is performed, where a small sample of tissue is taken and analyzed. The results of the scope and biopsy will help diagnose an individual with IBD, as well as with the specific type of IBD that they have. If further testing is needed, your doctor may recommend other options such as an ultrasound, MRI (magnetic resonance imaging), or a CT (computed tomography) scan.4,6,7

How is inflammatory bowel disease treated?

Treatment for IBD depends on the severity of the condition, previous treatment response, treatment side effects, and other medical conditions the patient may have. Mild to moderate cases are often treated with anti-inflammatory medications or antibiotics that can be used on a long-term basis. Antibiotics may also be specifically used as a short-term treatment for some of the complications from IBD, such as abscesses or wound infections.6,7

For moderate to severe cases, or when other medications have not been effective, biologic therapies may be used. (Some of the same biologic medications used to treat AS are also used to treat IBD.) Immune system-suppressing medications are also used for moderate to severe cases, often along with another medication. Corticosteroids are often prescribed as a short-term treatment for some symptoms of IBD, although they do not treat the underlying causes of those symptoms. In some cases, surgery may be needed to remove diseased portions of the digestive tract, most often the small or large intestine. Often, the intestine can be reconnected after the disease portion is removed, but sometimes may require the formation of an external stoma (i.e. ileostomy or colostomy) or an internal pouch (i.e. j-pouch). 6,7