Lupus is an autoimmune disease. The immune system that normally protects you from invading bacteria and viruses runs amok. It attacks parts of your own body as if it were an outside invader. There is a list of symptoms and disorders that doctors use to help decide whether you have lupus. Not everyone with lupus has everything on the list. But you have to have a certain number in order to be diagnosed.
One of the items on the list is renal disease - the medical name for kidney disease. The kidney disease of lupus can show itself in several different ways. It can range from mild to severe. When lupus attacks the kidneys, antibodies from your immune system link to antigens in your body to form immune complexes. These immune complexes circulate in blood and travel to the kidneys. Both kidneys are affected in the same way.
Just as lupus causes inflammation in other areas of the body, it causes inflammation in the kidney, which is called nephritis.
How Kidneys Work
The kidneys are filters. Blood flows into your kidneys, and waste in your blood is filtered through your kidney's filtering mechanisms - called glomeruli. Then that waste comes out of your body in your urine.
If the filtering process is damaged, less waste comes out in your urine - and the waste level is higher in your blood.
Types of Kidney Problems
- Proteinuria - An examination of your urine shows that protein is present. If the filtering process starts to fail, the first thing that happens is that protein from the blood can leak through the filtering apparatus. It is the earliest sign of a kidney problem.
- Progressive renal failure - The filtering function is increasingly failing.
- Nephrotic syndrome - The first symptom is that your body gets swollen. This may be difficult to spot in someone who takes steroids such as prednisone, which can also cause swollen feet and puffy eyes. So the doctor has to sort out the source of the swelling by considering when it started and other issues.
- Hematuria - This is blood in the urine. You usually can't see it. But it can be seen under a microscope.
- Hypertension - This is high blood pressure. The kidneys and high blood pressure are common partners. High blood pressure can cause kidney problems. And kidney problems can lead to high blood pressure. So if a person with lupus has high blood pressure, it's not uncommon for there to be a kidney problem lurking. But hypertension can also be caused by prednisone and have nothing to do with the kidneys.
Tests for Kidney Problems
Urine tests look for protein and blood in the urine. Some may be done with a simple dip stick. Others have to go to the lab. Sometimes the doctor will ask you to collect all of your urine over a 24-hour period and bring it in - to find out how much protein you are losing over 24 hours.
Blood tests are also important. Your doctor tests for a marker of waste in the blood called creatinine. If it's high, the kidney is not filtering well. That test is a normal part of anyone's regular check-up. A healthy level is about .7 to 1.4, depending on the patient. If your level was 1.2 six months ago and now it's 1.8, maybe there's a problem. If it rises further to 2.4, that's progressive renal failure.
Kidney biopsy involves inserting a needle into the kidney to withdraw samples of the kidney tissue. The patient lies face down in a room where a sonogram or CAT scan procedure is done. (Painless sound waves are used to locate the kidney.) Lidocaine is injected in the area to numb it. You must be awake for the procedure because you will have to hold your breath. If you breathe, the kidney will move.
When the sample is removed, it is analyzed right away to make sure it is adequate. Two or three samples are taken. The doctors try to make you comfortable during the procedure. If you need to get up to go to the bathroom, you can. Overall, it takes about 45 minutes. The most serious possible complication is bleeding, but that's not common.
When should a kidney biopsy be done? That's controversial. Basically, a kidney biopsy should be done to find out whether there is anything serious going on if urine and blood tests suggest there may be trouble. A biopsy should be done to help the doctor make the decisions about treatment. So your doctor may recommend biopsy when there is rising protein in the urine or when there is blood in the urine or when your blood creatinine levels go up.
However, if you have active systemic disease - fever, joint pain, fluid in the lung - and require a certain amount of prednisone, it may be better to treat the underlying disease and wait to see what happens to your kidneys before doing the biopsy. Your kidneys may get better, as reflected in the urine, and the biopsy won't be necessary. Some doctors disagree with that approach.
However, if the blood creatinine is 2 or 3, then you know the problem is pretty severe and you may need to biopsy. In contrast, if the creatinine is normal but there's a little blood in the urine and the systemic disease is not active, the doctor wants to be able to predict what might happen and is likely to want a biopsy. So it's all a matter of clinical judgement.
Classification of Nephritis
The World Health Organization classifies kidney problems in the following way:
Class I - A little protein in the urine, with normal filtering function. These patients may need no treatment other than that needed for their other lupus problems.
Class II - Mesangial change in one area of the glomeruli - The mesangium is the structure that holds up the filtering units in the kidneys. In this class, there are some changes in one area of those units. Depending on how fast those changes are developing, the doctor may want to start treatment.
Class III - Active inflammation but in a patchy fashion with some areas remaining normal. The doctor wants to give advice on treatment
Class IV - Diffuse proliferative glomerular nephritis - Virtually all of the kidney is involved in inflammation.
Class V - Membranous nephritis- New deposits have gotten stuck on the filtering membrane and have not elicited an inflammatory response - The doctor may decide to leave it alone and watch it or to treat it intermittently.
Class VI - Advanced sclerosing (scarring) - The disease is beyond the point where it can be treated with the anti-inflammatory or immunosuppressant medications that normally help lupus. Instead, we treat with medications to try to prevent further scarring, which may or may not work.
Medications for Lupus Nephritis
- Oral corticosteroids, such as prednisone pills - This continues to be the main treatment for lupus.
- IV pulse steroids - This is large doses of steroids given intravenously (through a drip needle) for a few hours for two or three days at the beginning of each month. It is followed by no steroids or only 5 to 10 mg by mouth for the rest of the month. This has been shown particularly useful for those with Class III disease.
- Cyclophosphamide (brand named Cytoxan) - This is a chemotherapy drug that was developed for treating cancer. It is now used for lupus patients in much lower doses so that it does not cause the serious side effects seen in cancer chemotherapy. However, it can still affect fertility. So it is avoided in women in their 20s and 30s who hope to have children. This has been shown useful in those with Class IV disease.
- Mycophenolate (Cellcept) - This is a newer drug developed as an immunosuppressant in transplantation. It is now being used in lupus patients, although we don't have as much information on its benefits. It doesn't seem to have side effects as severe as steroids and cyclophosphamide.
- Azathioprine (Imuran) - This is an older immunosuppressant that may be used when other medications have been tried or to supplement them.
- IVIG - This is intravenous immunoglobulin. It is a product derived from human blood. It seems to help in the treatment of some autoimmune diseases. It is still in under research.
- Monoclonal anatibodies - Researchers are trying to develop antibodies that will attack certain B cells involved in lupus. It is thought that these B cells may be the ones that damage the kidney and that destroying them may provide a more focused way of treating lupus nephritis.
Kidney Failure
If all of these medications fail and there is an enormous amount of scarring in the kidney, the condition is called end stage renal disease (ESRD). This means the kidneys have failed. Uremic symptoms occur because of waste in the blood. This may include high blood pressure, shortness of breath, abdominal pain, muscle cramps, anemia, and other problems. Less than 10% of those who have lupus reach ESRD.
Although this is "the end" for the kidney, it is not "the end" for the patient unless left untreated. You still have good options for a long life. Dialysis provides treatment with an artificial kidney that filters your blood for three to four hours - three days per week - a dialysis center, or you can have peritoneal analysis at home. Kidney transplantation can provide you with a new kidney. Your nephrologist can discuss the pros and cons of the various options available to you.
When to see a Nephrologist
A nephrologist is a doctor who specializes in diagnosis and treatment of the kidneys. When should your primary care physician or rheumatologist refer you to a nephrologist? Or when should you ask for such a referral? If there is something wrong with the urine - protein or blood in the urine - it's probably best to have an evaluation by a nephrologist. Earlier is usually better. However, by the time there is any increase in the creatinine, a consultation with a nephrologist is absolutely necessary. That's proof that the filtering function is declining. Sometimes the nephrologist also gets involved when hypertension is difficult to control.
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