Kidneys

Where are the kidneys, and what do they do?

The kidneys are two bean-shaped organs that rest under your abdominal cavity, towards your lower back. Most people think of the kidneys as organs responsible for filtering blood and producing urine. However, the kidneys play other vital roles in the body, including the regulation of blood volume, blood pH, and blood pressure. The functional unit of the kidney is called the nephron. Each nephron functions like a mini-kidney to remove waste and unneeded substances from your body, while also ensuring that you retain vital nutrients and water.

How does lupus affect the kidneys?

About one half of people with lupus experience kidney involvement, and the kidney has become the most extensively studied organ affected by lupus. The part of the kidney most frequently troubled by lupus is a part of the nephron called the glomerulus, a tuft of capillaries that functions to filter substances from of the blood. For this reason, the type of kidney inflammation most commonly experienced in lupus is called glomerulonephritis. Fortunately, the prognosis for patients experiencing kidney lupus is improving due to the growing number of medications that physicians have in their arsenal.

What are the signs of kidney lupus? How is it diagnosed and classified?

Swelling of the ankles and abdomen may be a sign of kidney disease, but the problem with kidney lupus is that often people are not aware that it is occurring until they visit the doctor for lab tests and blood work. Testing for the disease includes urinalysis, which your doctor will check for items such as red blood cells, red blood cell casts, and protein that has leaked from your kidneys into your urine. In addition, she/he will most likely ask you to perform a 24-hour urine test and determine the efficiency with which your kidneys are filtering blood by measuring your creatinine clearance. Lastly, your doctor may also recommend you to a kidney doctor (called a nephrologist) to perform a biopsy to determine the class and degree of your kidney involvement. There are 6 levels of kidney lupus (Normal glomeruli, Mesangial disease, Focal proliferative glomerulonephritis, Diffuse proliferative glomerulonephritis, Membranous nephropathy, and Sclerosing nephropathy) and the class in which your disease falls will help your doctor to design a specific course of treatment.

What is the treatment course for lupus nephritis?

The treatment of lupus nephritis is highly individualized, but several drugs provide an arsenal from which your physician may choose. Corticosteroids are often used to reduce the inflammation involved in lupus nephritis, especially milder forms. Oral prednisone can be used, as can higher doses of methylprednisolone given in “pulses.” Another class of medications called immunosuppressives can also be used. These medications help to reduce your immune system’s attack on your kidneys by suppressing certain cells involved in this response. However, both corticosteroids and immunosuppressives make you more susceptible to infection, so it is important to speak to your doctor if you feel that you are developing one.

How is kidney lupus monitored?

As you return to your doctor’s office, she/he will most likely keep close watch on your kidneys to ensure that your kidney involvement is not worsening. There is no all-encompassing test for kidney function; instead, your doctor will use a number of tests to monitor your blood and urine. By obtaining a blood urea nitrogen (BUN) levels and blood creatinine levels, she/he can monitor how well your kidneys are filtering blood. In addition, you blood pressure will be monitored, since high blood pressure is an indication of kidney degeneration. High levels of protein in the urine (proteinuria) can indicate increased kidney involvement, since protein usually does not cross from your blood vessels into your kidney tubules and thus should not appear in your urine. In addition, tests of blood complement and anti-DNA antibodies can suggest inflammation that may be affecting the kidneys.

An important note about medications and blood pressure

Due to the silent nature of kidney lupus, it is very important that you take your medications daily as prescribed by your doctor. Even if you do not feel sick, inflammation in your kidneys and other organs can lead to permanent, irreversible scarring. Your medications can combat this inflammation right now, but permanent scarring will never go away. If kidney disease is allowed to progress without treatment, your kidneys will fail, and you will need to go to dialysis three times per week to have your blood filtered. The only way to get off dialysis is to have a kidney transplant, and organ transplant opportunities are not easy to come by. This information is not meant to frighten you, but merely to ensure that you understand how important it is to take your medications!

In addition, since the kidneys are tied intimately to the regulation of your blood pressure, it is imperative that you maintain a healthy blood pressure of 120/80 mmHg. If your doctor prescribes a blood pressure medication to keep your kidney lupus in check, be sure to take it exactly as prescribed. Limit your intake of salt to less than 3 grams per day, and try to eat a healthy, well-balanced diet. The prognosis for people with lupus nephritis does not have to be grim; it is important to remember that you play the most important role in keeping your body as healthy as possible!

Sources

  • Balow, JE, Boumpas, DT, Austin, HA. Renal Disease. In: Schur, PH, ed. The Clinical Management of Systemic Lupus Erythematosus. 2nd ed. Philadelphia: Lippincott – Raven; 1996:109-126.
  • Dooley, MA. Clinical and Laboratory Features of Lupus Nephritis. In: Wallace, DJ, Hahn, BH, eds. Dubois’ Lupus Erythematosus. 7th ed. Philadelphia: Lippincott Williams & Wilkins; 2007:1112-1130.
  • Wallace, Daniel J. The Lupus Book: A Guide for Patients and Their Families. 1st ed. New York: Oxford University Press, 1995. 139-145.