Lupus: How does it affect the kidneys?

Systemic lupus erythematosus (SLE) — usually referred to as lupus — is a chronic inflammatory disease. Although it can affect many parts of the body, the kidneys are especially vulnerable.

Normally, your immune system makes special proteins called antibodies that attack foreign invaders, such as bacteria and viruses. In an autoimmune disorder such as SLE, your immune system makes antibodies — called autoantibodies — that mistakenly attack your own tissues. Complexes of these autoantibodies build up in the small blood vessels (capillaries) of the kidneys and cause varying degrees of inflammation (lupus nephritis). This impairs kidney function and may lead to kidney failure.

Initially, lupus nephritis may cause no signs or symptoms. But in some people, it may eventually cause:

• High blood pressure
• Swelling (edema) of the feet and lower legs
• Blood in the urine

If you're diagnosed with lupus, your doctor will likely recommend tests to evaluate your kidney function. These tests may include:

• Urine test (urinalysis), which checks for an elevated protein level and red blood cells in the urine
• Serum creatinine, a blood test that measure the ability of your kidneys to excrete waste products

These tests may be repeated periodically. If a problem is detected, your doctor may recommend a kidney biopsy. The results of a biopsy help determine the severity of the kidney disease and appropriate treatment.