Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease where the body’s immune system mistakenly attacks its own healthy tissues. This condition can affect numerous organs, including the joints, skin, brain, lungs, and heart. The kidneys are frequently impacted, representing a serious complication of SLE.
How Lupus Affects Kidneys
Lupus affects the kidneys when the immune system produces autoantibodies that attack kidney tissues. These autoantibodies, along with immune complexes, can deposit in the tiny filtering units of the kidneys known as glomeruli. This triggers an inflammatory response, leading to lupus nephritis (LN). The inflammation impairs the glomeruli’s ability to filter waste products and excess fluid from the blood.
Lupus nephritis is categorized into classes based on the pattern and severity of kidney damage observed under a microscope. Class III (focal) and Class IV (diffuse) involve inflammation and damage to the glomeruli, varying in extent. Class V (membranous) primarily involves thickening of the glomerular basement membrane due to immune complex deposition. These classifications guide treatment strategies.
Recognizing Kidney Involvement
Kidney involvement in lupus can manifest through several signs and symptoms:
- Swelling (edema), often appearing in the legs, ankles, or around the eyes, due to the kidneys’ reduced ability to remove excess fluid.
- Foamy urine, resulting from high protein levels (proteinuria), indicating damage to the kidney’s filters.
- High blood pressure, as damaged kidneys struggle to regulate fluid and electrolyte balance.
- Fatigue, due to waste product buildup or anemia from impaired kidney function.
- Changes in urination frequency, like needing to urinate more often at night.
Diagnosing Kidney Disease in Lupus
Diagnosing kidney disease in lupus involves medical tests to assess kidney function and identify the presence and type of lupus nephritis. Urine tests, including urinalysis, check for protein and blood, which are early indicators of kidney damage. A 24-hour urine collection quantifies the amount of protein excreted over a day, providing a precise measure of proteinuria.
Blood tests provide further insights. Creatinine and blood urea nitrogen (BUN) levels assess how well the kidneys filter waste products. The estimated glomerular filtration rate (eGFR) is calculated from these values to measure kidney function. Complement and anti-dsDNA antibody levels are often checked, as these immune markers can indicate lupus disease activity and kidney involvement. A kidney biopsy, taking a small tissue sample, is the definitive diagnostic tool to confirm lupus nephritis, classify its type, and assess damage.
Treatment Approaches for Lupus Kidney Disease
Treatment for lupus kidney disease aims to reduce inflammation, preserve kidney function, and prevent kidney failure. Initial treatment often involves high doses of corticosteroids, such as prednisone, to quickly suppress the immune system and reduce kidney inflammation. Various immunosuppressants are then used to maintain disease control and allow for lower corticosteroid doses.
Common immunosuppressants include cyclophosphamide, mycophenolate mofetil, and azathioprine, which dampen the immune response attacking the kidneys. Newer biologic medications, such as belimumab and voclosporin, offer targeted approaches by interfering with specific immune pathways involved in lupus. Managing blood pressure is also a significant part of treatment, often with ACE inhibitors or ARBs, to reduce kidney strain and slow disease progression. For individuals whose kidney disease progresses to end-stage kidney failure, dialysis or a kidney transplant become necessary.
Long-Term Management and Outlook
Long-term management of lupus kidney disease centers on continuous monitoring of kidney function and disease activity. This involves regular doctor visits, with periodic blood and urine tests to assess creatinine, eGFR, protein levels, and immune markers. Consistent monitoring helps adjust treatment plans to maintain remission or stable kidney function.
Lifestyle adjustments also support kidney health. Adopting a healthy diet, low in sodium and saturated fats, can help manage blood pressure and reduce kidney burden. Maintaining hydration and engaging in regular, moderate exercise can promote overall well-being. Individuals with lupus nephritis should also discuss over-the-counter medications like NSAIDs with their doctor, as these can sometimes negatively impact kidney function. With proper treatment adherence and ongoing medical care, many individuals with lupus kidney disease can achieve remission or maintain stable kidney function, leading to a more favorable outlook.