Lupus nephritis is an inflammation of the kidney caused by the rheumatic condition systemic lupus erythematosus (SLE). Lupus affects the skin, joints and brain as well as the kidneys.
An estimated one-third of people with lupus will develop nephritis that requires medical evaluation and treatment. Lupus nephritis is a potentially serious symptom of lupus.
Although the consequences of untreated lupus nephritis are serious, the symptoms are not always dramatic. They can vary from person to person and even from day to day in the same person. Symptoms include:
- Weight gain
- High blood pressure
- Swelling around the eyes, legs, ankles or fingers. This is often the first noticeable symptom. The swelling is usually absent in the morning. It gradually gets worse as a person walks about during the day
- Dark urine
- Foamy, frothy urine and the need to get up to urinate during the night can suggest a loss of protein in the urine
- In severe cases, kidney failure can occur
Causes and Risk Factors
It is not yet known what causes lupus. Some possibilities under investigation are infections and viruses or environmental causes. There are some indications that there may be an inherited factor to lupus. Lupus affects more women than men.
Because symptoms can vary from person to person and even within the same person from day to day, diagnosing lupus nephritis can be challenging.
Symptoms may be present at one examination and gone the next. Additionally some of the medications used to treat lupus can cause symptoms that can be mistaken for those of lupus nephritis.
A doctor will take your medical history, do a thorough examination and evaluate your symptoms. He or she may order the following tests:
- X-rays of the kidneys
- Blood tests. These are done to see if the kidney is effectively removing waste products from the blood. Additionally, if there is a loss of protein in the urine, a blood test can show if there is a lower level of protein in the blood. Blood tests can also show is there are imbalances of salt and water in the blood. Finally, blood tests can show the presence of antibodies that are typically high in persons who have lupus nephritis.
- Urine tests. A urinalysis is the simplest and most common test used to find out if a person has lupus nephritis. A urinalysis will check for the presence of red and white blood cells in the urine or high levels of protein.
- Imaging studies. Two of these types of studies - an intravenous pyelogram and a sonogram - are usually done before a kidney biopsy. In an intravenous pyelogram, dye is injected into the body and collects in the kidneys. An X-ray is taken that shows the outline of the kidneys with the dye. A sonogram uses soundwaves transmitted through the body and their echoes to show the shape and size of the surfaces of the kidney.
- A biopsy of the kidney. This test involves taking a sample of kidney tissue to examine under a microscope. If blood and urine studies suggest lupus nephritis, a biopsy is done to confirm the diagnosis. A biopsy can also help find out how widespread and severe the kidney disease is. A biopsy is most often done by inserting a narrow needle through the skin of the back and removing a small piece of kidney. (Rarely, the procedure may be done in an operating room surgically.)
Treatment depends on the symptoms and must be tailored to the individual.
Medicines can decrease swelling, lower blood pressure, and decrease inflammation by suppressing the immune system. Sometimes drugs to prevent blood clots are also prescribed. High doses of corticosteroids may be prescribed until the lupus nephritis improves. Because corticosteroids can cause a variety of side effects including fluid retention, moodiness, loss of mineral from the bones and cataracts, they must be monitored carefully. The dosage of corticosteroids prescribed for lupus nephritis is usually tapered down once the symptoms improve.
Another type of drug that may be prescribed is cytotoxic drugs or drugs that suppress the immune system. These are typically given to people who have lupus nephritis to prevent kidney damage.
Patients may need to limit protein, sodium and potassium intake in their diet. Maintaining a healthy weight is also important.
Even with treatment, some people with lupus nephritis continue to lose kidney function. In the event that both kidneys fail, it may be necessary to have dialysis. Dialysis involves filtering the blood through a machine so that waste products can be removed from it before the blood is returned to the body. Ultimately, kidney transplantation may be needed. Persons with lupus can successfully have kidney transplantation if the surgery is done at a point in time where they do not have active lupus. After transplantation, they will need drugs to suppress the body's immune system to avoid having the transplanted kidney rejected.
Thanks to major advances in the understand and treatment of lupus nephritis, more than 80% of people with lupus nephritis will live a normal life span.