Rheumatoid arthritis (RA) has many health consequences, and mounting evidence suggests that an increased risk of kidney disease is one of them. Kidney disease also boosts the odds of developing heart disease. Since people with RA already have double the average risk for cardiovascular disease, that can spell serious trouble.

How does RA affect my kidneys?

According to a 2014 Mayo Clinic study, people with RA have a one in four chance of developing kidney disease compared with a one in five chance for people who don’t have it.  Considering that some 1.5 million Americans have RA, that difference could spell an additional 75,000 cases of kidney disease in these patients.

In an earlier French study of 129 RA patients, known as the MATRIX study (MeThotreXate And Renal Insufficiency), 46 percent of patients showed some degree of kidney disease. Among those who did, most had either normal kidney function with signs of kidney damage or low kidney function with signs of kidney damage.

One type of kidney problem common in patients with longstanding RA is amyloidosis. In this condition, “a special type of protein gets deposited that causes kidney failure,” says Eric Matteson, MD, chair of rheumatology at Mayo Clinic in Rochester, Minn. In one Finnish study, nearly 6 percent of RA patients were found to have this condition. (The rate is thought to be lower in the U.S.)

RA patients may also have other types of kidney disease, although the exact type is not always determined. “Most patients with RA and chronic kidney disease do not undergo a kidney biopsy,” says LaTonya Hickson, MD, a nephrologist at Mayo Clinic. Among patients who did get biopsies, “a variety of renal diseases have been found, including amyloidosis, membranous glomerulonephritis [a buildup of immune substances within the kidney], and other glomerular diseases [those that affect the tiny filters in the kidneys]. We may begin to see a different pattern of renal diseases in the future as novel therapies emerge.”

Science behind the RA-kidney link

Experts believe that RA might increase the risk for kidney problems in two main ways. 

Inflammation. “We think it’s the overall inflammatory burden of the disease” that contributes to kidney dysfunction, says Dr. Matteson, lead author of the recent Mayo Clinic study. “Just like you have increased heart disease risk because of how the inflammation affects your blood vessels, the same is true for the tiny blood vessels in your kidneys.” The more severe your disease, the higher your risk of poor kidney function, he says.

Medications. Most of the medications taken for RA are not directly toxic to the kidneys, says Donald Miller, PharmD, professor and chair of pharmacy practice at North Dakota State University. But some can cause problems if you already have reduced kidney function.   

- NSAIDS. Regular doses of over-the-counter (OTC) nonsteroidal anti-inflammatory drugs (NSAIDS), such as ibuprofen and naproxen, usually don’t pose a problem for relatively healthy people, says Miller. However, all NSAIDs (including the prescription celecoxib) reduce blood flow to the kidneys. This could be dangerous for those with reduced kidney function, which includes many older patients.

- Corticosteroids. Corticosteroids such as prednisone cause fluid retention, which can raise blood pressure. Overtime, this can aggravate kidney disease, says Miller.

- Methotrexate.  This disease-modifying anti-rheumatic drug (DMARD) is eliminated through the kidneys. If your kidneys aren’t working as well as they should be, the drug could build up in your bloodstream, potentially causing an overdose.

- Cyclosporine. A powerful immunosuppressant, cyclosporine may cause reversible decreases in kidney function. About “half of patients develop mild kidney problems while on cyclosporine, and may need to adjust their dosage or discontinue the medication,” according to the American College of Rheumatology. Kidney function usually improves after the drug is stopped.