The Renal (Kidney) System
Lupus is an autoimmune disease that can affect almost any part of your body, most often your joints, skin, kidneys, heart, lungs, blood, or brain. Your two kidneys are part of your renal system, which also includes two ureters, the bladder, and the urethra. As the primary organs of the renal system, your kidneys are responsible for:
- maintaining the correct amount and type of body fluids
- getting rid of waste products and toxic substances
- regulating the hormones (chemical messengers) that help control blood pressure and blood volume
Lupus Nephritis
Inflammation of the nephrons, the structures within the kidneys that filter the blood, is called glomerulonephritis, or nephritis. Lupus nephritis is the term used when lupus causes inflammation in your kidneys, making them unable to properly remove waste from your blood or control the amount of fluids in your body. Abnormal levels of waste can build up in the blood, and edema (swelling) can develop. Left untreated, nephritis can lead to scarring and permanent damage to the kidneys and possibly end-stage renal disease (ESRD). People with ESRD need regular filtering of their body’s waste done by a machine (dialysis) or a kidney transplant so that at least one kidney is working properly.
Lupus nephritis most often develops within the first five years after the symptoms of lupus start, and usually affects people between the ages of 20 and 40. It is estimated that as many as 40 percent of all people with lupus, and as many as two-thirds of all children with lupus, will develop kidney complications that require medical evaluation and treatment. Because there are so few symptoms of kidney disease, significant damage to your kidneys can happen before you are diagnosed with lupus.
In the early stages of lupus nephritis, there are very few signs that anything is wrong. Often the first symptoms of lupus nephritis are weight gain and puffiness in your feet, ankles, legs, hands, and/or eyelids. This swelling often becomes worse throughout the day. Also, your urine may be foamy or frothy, or have a red color. Often the first signs of lupus nephritis show up in clinical laboratory tests on the urine. That is why testing your urine is so important.
Nephrologists are the physicians who treat the renal system. The tests they will use to diagnose lupus nephritis are: collection of urine, usually over a 24-hour period; blood tests; and often, a kidney biopsy.
Urinalysis
Because your body’s waste matter is processed by your kidneys, testing a sample of your urine can show any problems with the way your kidneys are functioning. The most common tests look for cell casts (fragments of cells normally found in the blood, or fragments of the tubules of the kidneys) and proteinuria (protein being spilled into your body because your kidneys are not filtering the waste properly).
Blood Tests
Certain blood tests can provide information about kidney damage and how well your body is filtering waste. The creatinine blood test is usually ordered along with a blood urea nitrogen (BUN) test to assess kidney function. A combination of blood and urine creatinine levels may be used to calculate a creatinine clearance. This measures how effectively your kidneys are filtering small molecules like creatinine out of your blood. Serum creatinine measurements (along with your age, weight, and gender) are used to calculate the estimated glo-merular filtration rate (EGFR), which is used as a screening test for evidence of kidney damage.
Kidney Biopsy
A kidney biopsy is done in a hospital. While you lie on your stomach your nephrologist will insert a very thin, long needle through the skin of your back and remove a tiny piece of tissue from one of your kidneys. The tissue will be examined under a microscope to determine how much inflammation or scarring is present.
Treatments
Even though lupus nephritis is among the more serious complications of lupus, there are effective treatments. Prednisone and other corticosteroids are generally prescribed to stop the inflammation. Immunosuppressive drugs may also be used (with or in place of steroid treatments), such as cyclophosphamide (Cytoxan®), azathioprine (Imuran®), cyclosporin A, and mycophenolate mofetil (CellCept®). Medications developed for other illnesses are also being studied as treatments for lupus nephritis, including rituximab (Rituxan®), and eculizuimab (Soliris™).
Most people who develop lupus nephritis will live a normal lifespan as long as they continue to receive proper treatment.
Other Lupus-Related Kidney Disorders
Not all kidney problems in people with lupus are due to lupus nephritis.
- Infections of the urinary tract, causing frequent urination or burning when urinating, are quite common.
- Fluid retention or even loss of kidney function can be a side effect of non-steroidal anti-inflammatory drugs (NSAIDs) and medications such as aspirin.
- Interstitial nephritis, which is inflammation of the connective tissue inside the glomerulus, can be a side effect of anti-inflammatory medications or antibiotics.
- Thrombosis and vasculitis, two blood-related lupus symptoms, can damage the kidneys and may even cause kidney failure.
- Lupus cystitis, which is inflammation of the lining of the bladder, may cause frequent urination and is associated with abdominal discomfort, including vomiting and weight loss.
Related Information
Kidney Disease & Lupus
Summer 2007 issue of Lupus Now magazine
Kidney Issues and Lupus
March 2010 -- 15 Questions with Dr. Michael Madaio
Kidney Involvement & Lupus
March 2009 webchat transcript with Dr. Brad Rovin
Kidneys and Lupus
March 2008 webchat transcript with Dr. James Tumlin
Kidney Involvement and Lupus
March 2007 webchat transcript with Dr. Ellen Ginzler
Frequently Asked Questions
What are the 5 stages of lupus and how do they progress into the next stage?
There are not stages of lupus per se. When people talk about early stage or late stage they are using those terms very loosely. They may generally mean the early development of lupus when symptoms are just beginning to show and those that the lupus has progressed to a point where there may be organ damage or the person has become debilitated or anywhere in between. No one can predict how a persons disease will or will not progress. Each person with lupus is different.
Lupus nephritis (kidney involvement) has classes, not stages. The World Health Organization has classed lupus nephritis and other kidney diseases into 5 classes. You do not necessarily progress from an "early" class to a "late" class although you can switch classes.
How can I be sure my organs are not being affected? When I go to the doctor for blood work every six months, does that blood work let the doctor know if there is any organ problem? Or is there a certain test that has to be done to check my kidneys?
Every patient with lupus should have screening tests of kidney function, including blood urea nitrogen (BUN) and serum creatinine. These blood tests show how well the kidneys are functioning to eliminate wastes. The urine should be examined to look for protein and blood cells, called urine sediment, which may be due to inflammation in the kidneys. If these tests are normal, they are usually repeated at intervals of about 3-6 months. If lupus is active in other systems besides the kidneys, or if there is evidence of protein or blood cells in the urine, these tests should be repeated much more frequently -- usually every month. A small amount of worsening can be detected before severe changes occur. Lower doses of prednisone or other medications may reverse the abnormalities if detected early. Test to check liver function should be done on a periodic basis also. Talk to your doctor about lab studies.
If you have lupus renal blood work done and it shows you are in remission -- when you do a 24 hr. urine -- can that still be higher than usual or will the protein be lower? I know there will always be a certain amount of protein in urine due to the lupus. What is considered "normal," under 1,000 or lower?
Normal urine protein excretion is less than 150 mg/24 h. For "Complete Remission," there should be less that 150 mg/day (or close to it). Serum BUN and creatinine levels (other measures of kidney function) return to normal in complete remission. Substantial reductions in proteinuria, that do not "normalize" (e.g. drop from greater than 3500 mg to between 150 – 2000 mg/day) are termed "Partial Remission." Patients who have a complete or partial remission have a better prognosis (with respect to kidney disease) than those do not.
In some patients, partial remission indicates ongoing inflammation whereas in others, persistent proteinuira results from scarring associated with the healing process. In the former situation, additional immunosuppressive therapy may be indicated.
In the latter situation, additional immunosuppressive therapy is not effective; however use of anti-hypertensive agents that also reduce proteinuria (e.g. ACEI or ARB drugs) are effective in slowing disease progression. The goal in the latter situation is to reduce proteinuria as much as possible or at least to less than 2000 mg/day, if possible. Renal biopsy may be needed to distinguish between these alternatives.
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