Kidney Disease And Lupus

CLINICAL COURSE OF LUPUS NEPHRITIS

The clinical course of lupus nephritis is highly variable. Often findings of lupus nephritis are evident only in urine studies. In many patients, the urine abnormalities are very mild and may be present on one examination and absent the next. This form of lupus nephritis is rather common and, generally does not require any special medical evaluation or treatment. However, in some patients, the abnormal findings on urine studies persist or may even worsen over time. Patients with this type of lupus nephritis are at risk for loss of kidney function. They may require additional studies to evaluate the extent of their lupus nephritis and to determine the best treatment approach to control their disease.

It is important to recognize that not all kidney problems in patients with lupus are due to lupus nephritis. For instance, infections of the urinary tract with burning on urination are quite common in lupus patients and require antibiotic treatment. Similarly, medications used in lupus treatment may produce signs or symptoms of kidney disease that can be confused with lupus nephritis. Salicylate compounds (e.g., aspirin), or non-steroidal anti-inflammatory drugs) are the most common type of medications used by lupus patients that can produce kidney problems. These drugs can cause loss of kidney function or fluid retention. These problems usually fade when the medications are discontinued.

STUDIES TO EVALUATE LUPUS NEPHRITIS

Urinalysis.

A urinalysis is by far the simplest and most commonly used study to test for lupus nephritis. In this test, a urine sample is examined for the presence of protein and blood cells which are not normally found in the urine. The protein or blood cells may collect within the tubules of the kidney and be excreted in the urine as "casts." Casts are identified by examining the urine under the microscope. The presence of protein (proteinuria), red blood cells (hematuria), white blood cells (leukocyturia), or casts in the urine suggests the possibility of lupus nephritis and generally indicates the need for further studies.

Blood Studies.

The major function of the kidney is to rid the body of waste products and excess fluids. Blood studies can be done to measure whether the kidney is carrying out this function properly. The blood urea nitrogen (BUN) and serum creatinine are two studies that are used to determine if waste products are being adequately removed by the kidney and not building up in the blood. The loss of protein in the urine may lead to a lowering of protein levels in the blood and is typically measured by the serum albumin. Imbalances of salt and water in the blood are detected by chemistry studies such as the serum sodium, potassium, and bicarbonate.

Blood tests may also be done to detect abnormalities of the immune system that are commonly seen in patients with lupus nephritis. Measuring the levels of serum complement and antibodies to DNA in the blood are two tests commonly used by many physicians to monitor lupus nephritis.

24-Hour Urine Collection.

Studies done on the urine collected over a 24-hour period are very sensitive in determining kidney involvement in a patient with lupus. These studies measure the kidneys' ability to filter waste products (creatinine clearance), and the exact amount of protein lost in the urine over a 24-hour period (24-hour urine protein).

X-ray Studies.

The size and shape of the kidneys can be determined by an intravenous pyelogram or sonogram. These studies are commonly done before a renal biopsy to help guide the physician doing the biopsy.

Kidney Biopsy.

In patients with evidence of lupus nephritis as determined by urine or blood studies, a kidney biopsy may be performed. The biopsy is done to confirm the diagnosis of lupus nephritis, and to determine the extent and severity of kidney disease. A kidney biopsy requires hospitalization of the patient. The biopsy is most commonly done by inserting a needle through the skin of the back and removing a small piece of the kidney. On rare occasions, a kidney biopsy may need to be done surgically in the operating room.

The specimen of the kidney obtained by the biopsy is examined under a microscope to determine how much inflammation or permanent damage (scarring) is present within the kidney. These findings are used to classify the type of lupus nephritis present. The four most common types of nephritis are mesangial nephritis, focal or diffuse proliferative nephritis, and membranous nephritis. Knowledge of the type of lupus nephritis is helpful in deciding on the best approach to drug treatment.

TREATMENT

The two major forms of drug therapy used in the specific treatment of lupus nephritis are corticosteroids to control inflammation within the kidney, and cytotoxic or immunosuppressive drugs to suppress the activity of the immune system.

Corticosteroids, such as Prednisone, Prednisolone or methylprednisolone (Medrol) are often used to treat lupus nephritis. Although corticosteroids have been used for nearly four decades in the management of lupus nephritis, there are still many unanswered questions as to exactly how they work and how they may be most effectively used. In general, high doses of corticosteroids, either taken orally or intravenously, are given until improvement in the lupus nephritis is seen. The dose of corticosteroids is then slowly reduced under careful observation of a physician to make certain that the nephritis doesn't worsen.

High doses of corticosteroids, or even corticosteroids given for extended periods time, may cause a number of adverse side effects. These include increase in appetite and fluid retention with weight gain, fullness of the face, easy bruising, moodiness, loss of mineral from the bone, cataracts, thinning of the hair, and an increase in the risk of infection and diabetes. Some of these side effects can be minimized by changes in diet, such as reducing the number of calories and following a diet that is low in salt.

Cytotoxic or immunosuppressive drugs such as azathioprine (Imuran) or cyclophosphamide (Cytoxan) are often used in patients who do not respond to corticosteroid treatment. These drugs block the function of the immune system which in turn serves to prevent further damage to the kidneys. There is clear evidence from research studies that these drugs may be beneficial in patients with severe lupus nephritis. However, the use these drugs in lupus nephritis is controversial, mainly because of the serious complications associated with their use.

Several experimental therapies for lupus nephritis appear promising and are the subject of intense investigation. These include newer immunosuppressive drugs like cyclosporine, the removal of antibodies associated with lupus nephritis by selective plasmapheresis, and the administration of biologic agents that suppress the immune system.

RENAL FAILURE

Over the past several decades, there have been major advances in the understanding of what causes lupus nephritis and, in particular, improvements in ways to treat patients with lupus nephritis.