Co-Occuring Bowel Issues in Ankylosing Spondylitis

The unresolved link between bowel inflammation and the immune system

People with ankylosing spondylitis may also experience problems with their digestion. As many as 30% of people with ankylosing spondylitis have symptoms that fit the criteria for irritable bowel syndrome (IBS). Between 6% and 14% of people with ankylosing spondylitis also live with a type of inflammatory bowel disease (IBD).

It’s thought that ankylosing spondylitis is associated with particular genes. Genetics plus other environmental factors may lead to inflammation that affects the spine and other body systems, including the digestive system.

This article will cover the bowel symptoms and problems connected to ankylosing spondylitis. 

Person experiencing abdominal pain and cramping

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Reported Bowel Issues in Ankylosing Spondylitis

Ankylosing spondylitis is one form of a group of conditions called spondyloarthritis. Even though they are forms of inflammatory arthritis and affect the musculoskeletal system, they are also associated with inflammation of the gut.

This inflammation can be acute (sudden) or chronic (long-lasting). It can cause many symptoms or could be part of another disease process.

A set of guidelines called the Rome Criteria can determine if the digestive symptoms someone is having stem from a functional bowel disorder. One study showed that about 40% of people with ankylosing spondylitis also meet the criteria for a functional bowel disorder. Of those, about 70% had chronic diarrhea. About 12% had symptoms that fulfilled the criteria for IBS.

Symptoms of IBS

Some of the symptoms that people with ankylosing spondylitis may have related to their bowels and a functional bowel disorder such as IBS include:

  • Abdominal pain 
  • Bloating
  • Constipation
  • Diarrhea
  • Distension

A large meta-analysis that included approximately 30,000 people found that as many as 7% of people with ankylosing spondylitis also have a form of IBD.

Symptoms of IBD

Some bowel symptoms may be a sign that inflammation is becoming more of a problem. These symptoms might prompt a healthcare provider to consider testing for a disease such as IBD:

  • Anemia (low levels of healthy red blood cells)
  • Blood in the stool
  • High amounts of a substance called calprotectin in the stool
  • Losing weight without trying

What Comes First, AS or GI Issues?

Changes in the microbiome (microbial communities) of the gut are thought to be part of the process of developing ankylosing spondylitis. The term for an imbalance in the bacteria and other microbes of the digestive system is dysbiosis. Dysbiosis causes a series of events in the body that lead to inflammation.

Besides leading to ankylosing spondylitis, the inflammation can cause symptoms in the digestive system, such as diarrhea. In some cases, the inflammation is thought to lead to diseases such as IBD.

Studies have shown that inflammation is found in the intestines of up to 60% of people with ankylosing spondylitis. The rate of Crohn’s disease (a type of IBD) is higher in people with ankylosing spondylitis than it is in the general population.

Genes play a role in the development of ankylosing spondylitis and IBD. But more factors in the process are complicated and not yet well understood.

People may be diagnosed with both ankylosing spondylitis and a bowel disorder, and both of these conditions may be the result of an imbalance in the gut microbiota or an inflammatory process.

Receiving a diagnosis of either one could come before the other. Getting a diagnosis may depend on the symptoms and whether they are bothersome enough to go to a healthcare provider and get tested.

In some cases, if a person is first diagnosed with an IBD and treated with an anti-tumor necrosis factor (anti-TNF) medication, it may delay the diagnosis of ankylosing spondylitis. This is because the anti-TNF medications treat IBD and might also be effective in treating ankylosing spondylitis, masking the symptoms. People with IBD who have chronic back pain should bring that up with their healthcare providers.

Treatment Considerations

As with any treatment plan, there will be advantages and disadvantages to each type of therapy. For people who have ankylosing spondylitis and also have bowel problems, there are going to be more considerations as to how to treat both.

Certain NSAIDS May Trigger Inflammation

Part of therapy for arthritis includes relieving pain. In the case of IBD and ankylosing spondylitis,non-steroidal anti-inflammatories (NSAIDs) might not be recommended for pain except for short periods.

The research is conflicting as to whether NSAIDs may cause IBD to flare up. However, in general, it’s recommended that NSAIDs not be used for the long term (more than two weeks) in people with IBD.

People with ankylosing spondylitis and IBS might see some benefits from the use of NSAIDs. One study showed that the rates of diarrhea and abdominal pain were slightly lower in people who used NSAIDs than in people who didn’t receive those drugs. It’s thought that for some people with ankylosing spondylitis, NSAIDs may help lower inflammation and prevent damage in the gut.

Oral and Injectable Steroids

Steroid injections or low doses of oral steroids might treat ankylosing spondylitis effectively. However, these treatments haven’t proved effective in helping treat inflammation in the gut caused by IBD.

To treat IBD, steroids are usually given in higher doses or in special gut-directed forms. For that reason, steroids might not be effective at treating both conditions.

Functional Bowel Disorder Treatments

For functional bowel disorders, there is less knowledge about how treatments may overlap and help with ankylosing spondylitis. Therapies aimed at functional bowel problems will vary depending on the diagnosis.

Some treatments that can help with functional problems in the gut include medications, fecal microbiota transplants, probiotics, prebiotics, diet changes, and psychological therapies. There are not enough studies yet to show if these treatments will also help with symptoms of ankylosing spondylitis.

The Gut-Brain Axis

One element of some bowel disorders that has recently become better recognized and described is the brain-gut axis. There is a complex connection between the intestinal tract and the brain involving many factors. What this means is that what’s going on in the brain can affect the digestive tract.

Therapies such as talk therapy, hypnosis, mindfulness, and medication may prove effective for treating some symptoms of bowel disorders. Including a mental health professional who can deliver this care to people who live with chronic illnesses such as ankylosing spondylitis and a bowel disease or disorder is becoming more common.

Seeing a mental health professional could also help treat some of the symptoms of ankylosing spondylitis. For instance, learning ways to manage pain may prove helpful. Having a chronic illness is stressful by itself, and a mental health professional can also share ideas for how to better cope with its ups and downs. 

Managing Bowel and AS Inflammation

In some cases, the treatments for ankylosing spondylitis and bowel inflammation may be the same. 

Disease-Modifying Antirheumatic Drugs

Methotrexate and Azulfidine (sulfasalazine) are disease-modifying antirheumatic drugs (DMARDs) that treat ankylosing spondylitis. Methotrexate might treat IBD either alone or in combination with another drug, but it is not as effective for treating ulcerative colitis. Sulfasalazine has not proved as effective in treating Crohn’s disease in the small intestine.

Anti-Tumor Necrosis Factor

Anti-TNF drugs often treat both ankylosing spondylitis and IBD in the same person. They may help in the event that DMARDs prove ineffective. Monoclonal antibodies and Janus kinase (JAK) inhibitors are two more classes of drugs under study that may treat ankylosing spondylitis and IBD.


Ankylosing spondylitis is associated with changes in the gut microbiome and inflammation in the digestive system. People with ankylosing spondylitis are more likely to have digestive symptoms and even inflammation in their gut. They have higher rates of functional bowel disorders and inflammatory bowel diseases.

Some treatments might work for both conditions, but others will only be effective for one or the other.

A Word From Verywell

If you have ankylosing spondylitis and are experiencing problems such as stomach or abdominal pain, cramping, upset stomach, bloated stomach, diarrhea, or constipation, bring this to the attention of a healthcare provider. Report any sign of blood in the stool or rectal bleeding immediately.

Your symptoms may result from a functional bowel disorder or IBD. When diagnosed, you must work with a healthcare provider to manage both conditions effectively.

Frequently Asked Questions

  • Do all ankylosing spondylitis patients have IBD?

    No, not all people who are diagnosed with ankylosing spondylitis are also diagnosed with a form of IBD. The percentage of people with ankylosing spondylitis who have IBD as well is higher than in the general population. One study of 30,000 people showed that the rate of IBD in ankylosing spondylitis might be as much as 7%.

  • What organs aside from the bowels can ankylosing spondylitis affect?

    Ankylosing spondylitis is unfortunately associated with several types of conditions outside of the spine that are often called extra-articular manifestations (EAMs). The most common EAM is anterior uveitis, which is an inflammatory condition that affects the eyes. Psoriasis, which is a condition that affects the skin, is also common.

  • What are signs of bowel incontinence related to ankylosing spondylitis?

    Some people may experience fecal incontinence (loss of bowel control) as a result of issues related to ankylosing spondylitis. Both IBS and IBD can cause incontinence because of diarrhea or constipation. Talk to a healthcare provider to get the underlying problem managed.

    Cauda equina syndrome (CES) is a rare condition (and medical emergency) that can occur with AS and may cause fecal incontinence. Other symptoms may include losing control of the bladder as well as neurologic symptoms such as numbness in the feet, difficulty speaking, and loss of balance. This is a result of the nerves at the bottom of the spine becoming compressed. It requires emergency treatment with steroids and/or surgery.

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By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.