Lupus and Kidney Involvement

Lupus In Color
Education Series

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Lupus Nephritis

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Lupus nephritis, or inflammation in kidneys caused by lupus, can make kidneys unable to properly remove waste from your blood or control the amount of fluids in your body. 

The rheumatologist is looking specifically for a blood test called the serum creatinine. This test measures kidney function and if it is elevated above normal levels or the patient’s baseline level it could indicate kidney dysfunction from lupus nephritis. 

Although kidney disease can occur silently there are some things that will alert the patient to the possible involvement of the kidneys. These include the development of swelling especially in the ankles and lower legs. It is possible to see blood in the urine although that is fairly unusual in lupus nephritis because the blood is often at a level only detectable under the microscope. Sometimes as patients lose protein in their urine the urine becomes foamy in the toilet. Another sign of kidney involvement would be the development of high blood pressure.

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Lupus nephritis, the term used for kidney involvement in SLE, is classified according to kidney biopsy findings. The new classification system for lupus nephritis was developed a few years ago by the International Society of Nephrology and the Renal Pathology Society.  It is a modification of the previous World Health Organization (WHO) classification. There are 6 classes of lupus nephritis. Class I is almost never seen because it shows minimal changes and doesn’t have any clinical signs. The Classes that come to clinical attention are Class III, IV and V.  Class III and class IV are called proliferative lupus nephritis and are very inflammatory and can develop renal insufficiency fairly quickly.  The difference between Class III and Class IV is the percent glomerular involvement. Class V Lupus nephritis is also called membranous lupus nephritis. In this particular Class the immune complexes are made in lupus deposit on the urine side of the glomerular basement membrane. The glomeruli are the filtering units of the kidney, and as blood is filtered to form the initial urine, it is filtered across the glomerular basement membrane. In Class V the immune complexes are on the urine side of the glomerular basement membrane and they make the basement membrane leaky for protein. Class V lupus nephritis is characterized by a large amount of protein in the urine. Unlike class III and IV there is not a lot of inflammation in the kidneys. Therefore Class V tends to be less aggressive, does not usually present with kidney failure or abnormal kidney function, but can progress to towards kidney insufficiency over a long time if not controlled.

Inflammation in the kidneys with lupus nephritis is different than the inflammation of a kidney infection known as pyelonephritis. It is unusual to have pain with lupus nephritis. The kidneys do not reside in the low back,as many believe, but actually in the upper part of the back, right under the ribs. When there is kidney pain it is generally located higher in the back rather than in the low back.

What type of damage can lupus do to my kidneys? 

In lupus the body makes antibodies to its own proteins and these antibodies can combine with these protein targets to cause immune complex formation. In lupus nephritis these immune complexes deposit in the kidney and specifically in the filtering units of the kidney called the glomeruli. This is where blood comes in to be filtered and waste products are excreted in the urine. These immune complexes can deposit in various places in the glomeruli and cause different types of damage to the kidney. In severe lupus nephritis they cause inflammation of the glomeruli along with destruction of the capillaries in the glomeruli. In other types of lupus nephritis the immune complexes cause damage to the filtration surface of the glomeruli and cause them to leak protein and blood into the urine. The inflammation in the kidney, or leakage of large amounts of protein through the kidney, can cause damage to the kidney, and if left unchecked and untreated overtime can cause kidney failure requiring renal replacement therapy.

Lupus itself does not usually predispose to kidney infection. However the medications used to treat lupus and lupus nephritis suppress the immune system making the patient more susceptible to infections of any type and these could include urinary tract infections.

Partial information compiled from
http://www.lupus.org/resources/15-questions-kidney-issues-and-lupus
Please visit the link for more in depth information and as always check with your doctor for the best information related to your specific case.

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