Kidney Disease
It is important to recognize that not all kidney problems in people with lupus are due to lupus nephritis.
- Infections of the urinary tract, with burning on urination, are quite common in people with lupus and require antibiotic treatment.
- Also, signs or symptoms of kidney disease that can be confused with lupus nephritis may be caused by some medications used in lupus treatment. These problems usually go away when the medications are discontinued. Two medications that can cause fluid retention or loss of kidney function are:
- -Salicylate compounds (e.g., aspirin)
- non-steroidal anti-inflammatory drugs (NSAIDs)
Studies To Evaluate Lupus Nephritis
There are a number of studies that can be done to test for kidney disease in a person with lupus:
1) 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 blood cells that may collect in the kidney to form and be excreted in the urine are called casts. Casts are seen when the urine is examined under the microscope.
- The presence of protein in the urine is called proteinuria.
- The presence of red blood cells in the urine is called hematuria
- The presence of white blood cells in the urine is called leukocyturia.
- The presence of any of these in the urine suggest the possibility of lupus nephritis and generally indicate the need for further studies.
2) Blood work
The main function of the kidney is to remove waste products and excess fluids from the body. Blood studies can be done to measure whether the kidney is doing this job properly.
- Two studies that are done to indicate whether waste products are being adequately removed by the kidney and not building up in the blood:
-the blood urea nitrogen (BUN) study
-the serum creatinine study. - Losing protein in the urine may lead to lower levels of protein in the blood. This is measured by:
- the serum albumin study. - Imbalances of salt and water in the blood are detected by chemistry studies such as:
- the serum sodium study
- the potassium study
- the bicarbonate study. - Blood tests may also be done to detect immune system abnormalities that are commonly seen with lupus nephritis. Two commonly used blood tests are:
- the serum complement test, which measures the levels of proteins in the blood that typically are low in lupus nephritis, and
- the antibodies to DNA test which measures these antibodies that typically are high in lupus nephritis.