How Rheumatoid Arthritis Can Affect the Kidneys
Rheumatoid arthritis (RA) has numerous health consequences and recent research suggests that an elevated risk of kidney disease is one of them. Kidney disease, consequently, increases the odds of developing heart disease. Patients with rheumatoid arthritis already have nearly double the risk for cardiovascular disease, adding kidney disease to the equation can spell serious trouble.
An autoimmune disorder, rheumatoid arthritis (RA) occurs when the body’s immune system mistakenly attacks the body’s own tissues, in the same manner that it would attack a foreign object found within the body. As the disease progresses, symptoms often spread to the wrists, knees, ankles, elbows, hips and shoulders. In many cases, symptoms occur simultaneously in the same joints on both sides of the body.
Symptoms that don’t involve the joints
According to the Mayo Clinic, approximately forty percent of patients with rheumatoid arthritis also experience signs and symptoms that do not involve the joint system at all. Rheumatoid arthritis can affect many non-joint structures including the skin, eyes, lungs, heart, kidneys, salivary glands, nerve tissue, bone marrow and blood vessels.
The kidneys—two, bean-shaped, fist-sized organs found in the lower back—are the body’s chief workhorses, filtering waste molecules from the blood for excretion in the urine, regulating the body’s electrolyte balance and maintaining the body’s delicate pH balance. Chronic kidney disease causes a progressive loss of kidney function over months or years, eventually resulting in death.
According to a 2014 Mayo Clinic study published in the American Journal of Kidney Diseases, individuals with rheumatoid arthritis have a one in four chance of developing kidney disease as compared with a one in five chance for people who do not have RA.
Researchers studied 813 Mayo Clinic patients with rheumatoid arthritis and 813 without it. The study also found that heart disease was more common among those with rheumatoid arthritis coupled with kidney disease. “That might not seem like a lot, but in fact that’s quite a big difference, and it has important implications for the course of rheumatoid arthritis and for the management of the disease,” said Eric Matteson, M.D., Mayo rheumatology chair and senior author of the study. In an earlier French study of 129 rheumatoid arthritis patients, known as the MATRIX study (MeThotreXate And Renal Insufficiency), 46% of patients showed some degree of kidney disease.
One type of kidney issue found within the rheumatoid arthritis population is amyloidosis—a group of diseases in which abnormal protein, known as amyloid fibrils, builds up in tissues in the body. With amyloidosis, “a special type of protein gets deposited that causes kidney failure,” says Dr. Matteson.
People with RA may also have other types of kidney disease, although the exact type is not always known. “Most patients with RA and chronic kidney disease do not undergo a kidney biopsy,” says LaTonya Hickson, MD, a nephrologist at Mayo Clinic. Among those rheumatoid arthritis patients who do undergo 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].”
Researchers believe that rheumatoid arthritis may increase the incident for kidney problems in two main ways: inflammation and medication.
Read on to learn more about the link between RA and kidney health.