Lupus Nephritis

Lupus nephritis is kidney inflammation caused by systemic lupus erythematosus (SLE), an autoimmune disease. It affects many people with lupus, often within the first few years after diagnosis, and is more common in people of African, Asian and Hispanic descent. It often causes no symptoms early on. Later signs include foamy urine, blood in the urine, swelling of the legs, ankles or around the eyes, weight gain from fluid, and high blood pressure. Without treatment it can lead to kidney failure, so regular urine tests are important for everyone with lupus.

Lab tests linked to lupus nephritis:

• Anti-dsDNA antibodies (quantitative): an antibody specific to lupus. Rising levels are often linked to active lupus nephritis.
• Protein/creatinine ratio: estimates how much protein is lost in the urine each day.
• Doctors also order a urinalysis with microscopy, kidney function (creatinine and eGFR), complement levels (C3 and C4), and a CBC. A kidney biopsy confirms the diagnosis and the type, which guides treatment.

How results are read:

• A urine protein/creatinine ratio of 0.5 g/g or higher in someone with lupus, or red cell casts in the urine, is a reason for further assessment, usually including a kidney biopsy.
• Rising anti-dsDNA with falling C3 and C4 suggests active disease, but these don't diagnose nephritis on their own.
• Response to treatment is tracked with urine protein, kidney function and urine sediment over months.

When to see a doctor:

• If you have lupus, keep up with regular urine and blood tests, even when you feel well.
• See a doctor promptly about new swelling, foamy or dark urine, or a rise in blood pressure.
• Get emergency care for severe breathlessness, chest pain, confusion or seizures.

Clinical takeaway: lupus nephritis is found with regular urine protein and kidney tests in people with lupus, and is confirmed with a kidney biopsy.