In some people, there’s a relationship between ankylosing spondylitis and kidney problems. Ankylosing spondylitis (AS) is a type of arthritis that affects the spine and sacroiliac joints. Those joints connect your spine to your pelvis. AS is a progressive disease that involves long-lasting inflammation. Uncontrolled inflammation can affect many parts of your body.
Symptoms and complications are different for everyone. Most people won’t get kidney problems due to ankylosing spondylitis. But it may not be as rare as once thought. Research shows kidney disease happens in 8%-35% of people with ankylosing spondylitis. You can have this condition and get kidney problems for a variety of other reasons.
What Kidney Problems Are Associated With Ankylosing Spondylitis?
One type of kidney problem people with AS get is secondary renal amyloidosis.
That’s when an abnormal protein builds up in organs, in this case the kidneys. As the buildup continues, the kidneys slowly lose their ability to function. Secondary amyloidosis happens in reaction to inflammatory conditions such as AS. This is also called “AA amyloidosis.”
A recent study says another damaging type of kidney lesions in AS is immunoglobulin A nephropathy (IgAN). The only way to confirm this is with a biopsy.
It’s not clear what causes IgAN, though it involves an immune system response. The immune system releases IgA, an infection-fighting protein, which can build up in the kidneys. This causes inflammation and, eventually, kidney damage.
People with AS can get chronic kidney disease (CKD), though other risk factors may also play a role.
The kidneys filter waste products out of the blood and keep salts and minerals in balance. In CKD, damaged kidneys can’t keep up, so waste products build up in the body. This can lead to other health problems, including heart disease, which can raise the risk of stroke and heart attack. Over time, progressive CKD can eventually lead to kidney failure.
Some research also suggests that people with AS – especially those who have had it a long time – are more likely to develop kidney stones than healthy people. Kidney stones are hard deposits of salts and minerals that form in the kidneys. You can often pass kidney stones when you urinate, but it can be very painful. Stones can also get lodged in the urinary tract or cause infection.
How Do Kidney Problems Happen?
The exact causes of kidney disease can be hard to pinpoint. Researchers have found more than 30 proteins that can form amyloid. Chronic inflammatory conditions, including AS, can trigger this type of protein buildup. In people with AS, there’s a strong association between elevated uric acid, known as hyperuricemia, and CKD.
Certain medications for inflammatory arthritis can also affect kidney function. These include:
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- High-dose disease-modifying drugs
Other conditions such as high blood pressure and diabetes can also impact the kidneys. So there may be several contributing factors.
What Are the Symptoms of Kidney Problems?
Symptoms depend on the specific problem. Symptoms of kidney amyloidosis can include:
- Low protein in your blood
- Too much protein in your urine
- High levels of cholesterol in your blood
- Tingling, burning, numbness in the hands or feet
- Anemia, when you don’t have enough healthy red blood cells to carry oxygen through your body
- Low blood pressure, which might cause:
- Problems concentrating
- Blurry vision
- Shortness of breath
- Weight loss
Symptoms of kidney disease may not be obvious in the early stages, but can include:
- Sleep problems
- Nighttime muscle cramps
- Lack of energy, feeling tired
- Swollen feet and ankles
- Puffiness around the eyes, especially in the morning
- Trouble concentrating
- Poor appetite
- Dry, itchy skin
- Frequent urination
Symptoms of IgAN may include:
- Blood in your urine
- Pee that looks foamy
If you have AS and any of these symptoms of kidney problems, see your doctor.
What Are the Risk Factors?
Aside from AS, other conditions can increase the risk of chronic kidney disease include:
- Heart disease
- High blood pressure
- Your kidneys are formed differently
Other risk factors are:
- Being Black, Native American, or Asian American
- Family history of kidney disease
- Older age
- Using medicines that can cause kidney damage
How Is It Treated?
Treatment depends on the type of kidney problem. For example, if you take medicines that can harm the kidneys, your doctor may recommend an alternative.
Treatment for secondary renal amyloidosis may include medicines to decrease inflammation, such as:
- Biologic agents, like tumor necrosis factor (TNF) blockers
- Monoclonal antibodies
- Dietary supplements such as fish oil
Other treatments may include:
- Antibiotics if there are signs of infection
- Diuretics (water pills) if you have swelling
- Iron supplements if you have anemia
There’s no cure for CKD, but treatments can help stop complications and slow disease progression. Some of these are:
- Blood pressure medicines: Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers can help control blood pressure and maintain kidney function.
- Diuretics (water pills): Can relieve swelling and keep fluids in balance.
- A phosphate binder: Can protect blood vessels from damage from too much phosphate.
- Statins: To manage cholesterol levels.
- Supplements: Calcium and vitamin D can help protect your bones.
- Hormonal treatment: The hormone erythropoietin can treat anemia.
- Dietary changes: Eating less salt can help reduce water retention. Your doctor may recommend a lower-protein diet to ease the workload on your kidneys.
Chronic kidney disease can sometimes lead to kidney failure. When that happens, treatment options include dialysis and kidney transplant.
If you have kidney problems, it’s important to speak with your doctor about which over-the-counter medicines and dietary supplements are safe for you. It’s also important to manage other conditions you may have.
Can Kidney Problems Be Prevented?
It may not be possible to prevent kidney problems in AS. However, it’s important to try to keep chronic inflammation under control. You can help manage AS and lower the risk of complications by following your treatment plan.
Ask your doctor about risk factors for kidney problems and what you can do to lower your risk. Here are some things you might want to bring up during your discussion:
- Review of your treatment plan and whether inflammation is well-controlled
- List of all your prescription and OTC medications and dietary supplements
- Other diagnosed health conditions
- Family history of kidney problems
- New or worsening symptoms
- Diet and exercise recommendations