Learning objectives
By the end of this chapter, the reader should be able to recognize renal involvement in SLE, interpret urine sediment and serologic activity markers, decide when kidney biopsy is indicated, integrate the 2018 ISN/RPS classification with activity and chronicity, select contemporary induction and maintenance regimens, plan reproductive and infection-risk management, and monitor response using proteinuria and eGFR trajectories.
Guideline currency. This chapter follows the KDIGO 2024 focused update of the lupus-nephritis chapter of KDIGO 2021. The update incorporates belimumab and voclosporin as add-on options in appropriate patients. The 2026 KDOQI commentary should be considered when applying the guideline in US practice.[inline_viewer url="https://kdigo.org/wp-content/uploads/2026/07/KDOQI-US-Commentary-on-KDIGO-2024-Lupus-Nephritis-GL.pdf"]
17.1 Clinical framing
Lupus nephritis is a clinicopathologic manifestation of SLE rather than a single disease. Immune-complex deposition, complement activation, endothelial injury, podocyte dysfunction, thrombotic microangiopathy, and chronic scarring may coexist in the same kidney. Renal activity can occur with modest proteinuria, while severe chronic damage can persist despite quiet serology. Consequently, treatment decisions should integrate symptoms, blood pressure, urine sediment, proteinuria, eGFR trajectory, serology, biopsy findings, and treatment toxicity.
The urgent presentations are rapidly progressive kidney dysfunction, nephritic sediment, nephrotic syndrome, malignant hypertension, suspected renal TMA, pulmonary hemorrhage, severe infection during immunosuppression, and pregnancy-associated disease. Stabilization, infection evaluation, nephrology–rheumatology coordination, and biopsy planning should proceed in parallel.
17.2 Pathobiology and clinicopathologic correlation
SLE autoantibodies, including anti-dsDNA and anti-nucleosome antibodies, form immune complexes that deposit in mesangial, subendothelial, and subepithelial locations. Complement activation amplifies leukocyte recruitment and endothelial injury. Subendothelial deposits are more strongly associated with inflammatory endocapillary lesions and nephritic features; subepithelial deposits produce capillary-wall injury and nephrotic proteinuria. Podocyte injury may cause nephrotic-range proteinuria even when glomerular proliferation is limited.
The kidney lesion may not be lupus nephritis. SLE patients can develop diabetic kidney disease, hypertensive nephrosclerosis, antiphospholipid-associated TMA, infection-related GN, drug-induced interstitial nephritis, or another glomerulopathy. A falling complement level or rising anti-dsDNA supports activity but does not replace clinical assessment or biopsy.
17.3 Clinical syndromes
Lupus nephritis may present with isolated albuminuria, microscopic hematuria, active sediment, nephritic syndrome, nephrotic syndrome, AKI, CKD, or a mixed pattern. Proteinuria should be quantified using ACR or PCR and interpreted with serum albumin and sediment findings. A threshold of 500 mg/day is a useful trigger for consideration of biopsy in many patients, but lower levels do not exclude important disease when there is active sediment, falling eGFR, or strong clinical suspicion.
17.4 Kidney biopsy and classification
Kidney biopsy is strongly indicated when the result is likely to change treatment, particularly with significant proteinuria, active sediment, unexplained eGFR decline, or suspected proliferative disease. It is not literally mandatory for every SLE patient with any abnormal urinalysis. Procedural risk, anticoagulation, thrombocytopenia, pregnancy, kidney size, and alternative approaches must be considered.
The 2018 ISN/RPS classification remains the principal histologic framework. Class I is minimal mesangial disease; Class II is mesangial proliferative disease; Class III is focal proliferative LN involving fewer than half of glomeruli; Class IV is diffuse proliferative LN involving at least half; Class V is membranous LN; and Class VI is advanced sclerosing LN. Class III and IV lesions may coexist with Class V. Every biopsy should report activity and chronicity lesions because the distinction informs reversibility and intensity of treatment.
| Clinical/pathologic domain | Interpretation | Management implication |
|---|---|---|
| Activity index | Endocapillary hypercellularity, leukocyte infiltration, necrosis, crescents, and interstitial inflammation | Supports potentially reversible inflammatory disease and treatment urgency |
| Chronicity index | Glomerulosclerosis, fibrous crescents, tubular atrophy, and interstitial fibrosis | Estimates irreversibility and limits expected response |
| Class III/IV | Proliferative lesions, often nephritic or mixed | Immunosuppressive therapy plus optimized supportive care |
| Class V | Subepithelial immune deposits; nephrotic phenotype is common | Risk-based therapy; evaluate proteinuria, albumin, thrombosis, and mixed lesions |
| TMA or podocytopathy | May occur with antiphospholipid syndrome, hypertension, or lupus podocytopathy | Requires mechanism-specific treatment rather than class-based therapy alone |
17.5 Diagnostic work-up
Evaluate blood pressure, volume status, edema, extrarenal SLE activity, medication exposure, pregnancy plans, infection risk, and thrombosis history. Obtain urinalysis with microscopy, ACR/PCR, serum creatinine/eGFR, albumin, CBC, electrolytes, and liver tests. Disease-oriented testing includes C3/C4, anti-dsDNA, ANA when diagnosis is uncertain, antiphospholipid antibodies when clinically indicated, and infection screening before immunosuppression. Consider SPEP, immunofixation, and serum free light chains when the phenotype is atypical or monoclonal disease is possible.
Urine sediment is a high-value test. Acanthocytes and RBC casts support glomerular inflammation; pyuria may reflect infection, interstitial nephritis, or lupus activity. Serology should be trended with proteinuria and eGFR rather than used in isolation.
17.6 Treatment of proliferative lupus nephritis
For active Class III or IV disease, induction combines glucocorticoids with mycophenolic acid analogues, low-dose intravenous cyclophosphamide, or selected multidrug strategies. Contemporary regimens generally favor rapid glucocorticoid reduction when clinically safe. Belimumab or voclosporin may be added to standard therapy in eligible patients; choice depends on eGFR, proteinuria, nephrotic severity, reproductive plans, infection risk, access, and drug interactions. Cyclophosphamide remains important in severe, rapidly progressive, life-threatening, or fertility-sensitive contexts when the regimen is carefully selected.
Hydroxychloroquine is generally continued unless contraindicated, with dose and retinal-toxicity monitoring. Before immunosuppression, address vaccination, hepatitis B, tuberculosis risk when relevant, Strongyloides risk in endemic settings, Pneumocystis prophylaxis when indicated, bone protection, fertility preservation, and contraception or pregnancy planning.
17.7 Class V and nonproliferative disease
Pure Class V disease is managed according to proteinuria, nephrotic complications, kidney function, and chronicity. Patients with low-level proteinuria may receive optimized supportive care and hydroxychloroquine with close monitoring. Nephrotic or progressive disease may require glucocorticoid plus mycophenolate, calcineurin inhibitor-based therapy, or another guideline-consistent regimen. Thrombosis prophylaxis is individualized using albumin, proteinuria, histology, prior thrombosis, bleeding risk, kidney function, and patient preference rather than a single albumin cutoff.
Class I or II disease generally receives hydroxychloroquine and supportive therapy, with treatment directed at extrarenal SLE unless there is an alternative active lesion. Class VI disease is managed as advanced CKD, including dialysis and transplantation planning; immunosuppression is not expected to reverse extensive global sclerosis.
17.8 Maintenance and monitoring
Maintenance usually uses mycophenolate or azathioprine with the lowest feasible glucocorticoid exposure. Duration is individualized, commonly extending for several years after complete response, especially in patients with proliferative disease or relapse risk. Monitor proteinuria, eGFR, urine sediment, blood pressure, CBC, liver tests, complements, anti-dsDNA, medication toxicity, infection, adherence, and reproductive goals.
A fall in proteinuria is a major response marker, but complete response should not be judged by proteinuria alone. Recurrent proteinuria with active sediment, declining eGFR, rising anti-dsDNA, or falling complement warrants reassessment for flare, chronic scarring, infection, drug toxicity, TMA, nonadherence, or a second kidney disease. Repeat biopsy may be useful when the distinction changes treatment.
Clinical pearls
- A kidney biopsy is strategic and strongly indicated in clinically significant renal disease, but is not mandatory for every minor urinary abnormality in SLE.
- Class III and IV lesions may coexist with Class V; treatment must account for both proliferative activity and nephrotic complications.
- Activity predicts reversibility; chronicity predicts the ceiling of recovery.
- Anti-dsDNA and complement trends support assessment but never substitute for sediment, proteinuria, eGFR, and clinical examination.
- Hydroxychloroquine is a long-term disease-modifying therapy unless contraindicated.
- Belimumab and voclosporin are add-on options for selected patients, not universal replacements for mycophenolate or cyclophosphamide.
- SLE patients can have non-lupus kidney disease; discordant pathology should trigger diagnostic reconsideration.
- Pregnancy planning must precede selection of teratogenic induction or maintenance therapy.
| Domain | Key interpretation | Clinical consequence |
|---|---|---|
| Biopsy activity | Necrosis, crescents, endocapillary and interstitial inflammation | Supports potentially reversible active disease and treatment urgency |
| Chronicity | Glomerulosclerosis, fibrous crescents, tubular atrophy, interstitial fibrosis | Estimates irreversibility and recovery ceiling |
| Class III/IV | Proliferative lesions, often nephritic or mixed | Immunosuppression plus optimized supportive care |
| Class V | Subepithelial deposits and nephrotic phenotype | Risk-based treatment and thrombosis assessment |
Summary
Lupus nephritis is a heterogeneous clinicopathologic syndrome. The nephrologist must identify urgency, quantify kidney involvement, interpret urine sediment and serology, and obtain biopsy tissue when the expected diagnostic value outweighs procedural risk. Current treatment is class- and risk-based, with optimized supportive care, hydroxychloroquine, glucocorticoid minimization, mycophenolate or cyclophosphamide, and selected add-on belimumab or voclosporin. Long-term outcomes depend on early control of activity, avoidance of treatment toxicity, adherence, reproductive planning, infection prevention, and monitoring of proteinuria and eGFR trajectories.
Question 1
An SLE patient has proteinuria 650 mg/day, dysmorphic RBCs, and a 20% eGFR decline over 3 months. What is the best next step?
A. Reassure because proteinuria is below nephrotic range B. Kidney biopsy if procedural risk is acceptable C. Start cyclophosphamide without diagnosis D. Repeat anti-dsDNA only
Answer: B. The combination of clinically significant proteinuria, active sediment, and declining eGFR makes biopsy likely to change treatment.
Question 2
Which statement about Class IV lupus nephritis is correct?
A. It is defined only by nephrotic proteinuria. B. It affects at least half of sampled glomeruli and commonly produces a nephritic or mixed syndrome. C. It never coexists with Class V disease. D. Chronicity is irrelevant to prognosis.
Answer: B. Class IV is diffuse proliferative disease; activity and chronicity must both be reported.
Question 3
A patient with Class III/IV LN has persistent proteinuria after induction. What is the most appropriate interpretation?
A. Persistent proteinuria always proves active inflammation. B. It may reflect activity, chronic scarring, TMA, podocytopathy, nonadherence, or another disease. C. Serology alone determines whether to intensify therapy. D. Repeat biopsy is never useful.
Answer: B. Persistent proteinuria requires integrated reassessment.
Question 4
Which treatment principle reflects the current KDIGO update?
A. Belimumab and voclosporin are contraindicated in LN. B. Add-on belimumab or voclosporin may be considered in selected patients receiving standard therapy. C. Cyclophosphamide is obsolete in severe LN. D. Glucocorticoids should remain at high dose indefinitely.
Answer: B. These agents are selected add-on options, with safety and eligibility assessment.
Question 5
A patient with nephrotic Class V LN has albumin 2.0 g/dL and no prior bleeding. How should thrombosis prophylaxis be approached?
A. Use a universal albumin cutoff. B. Never anticoagulate. C. Individualize thrombosis and bleeding risk with the patient. D. Use aspirin as an equivalent substitute in all cases.
Answer: C. Histology, albumin, proteinuria, prior thrombosis, bleeding risk, kidney function, and preferences all matter.
Question 6
A pregnant patient with active LN requires treatment planning. Which principle is most important?
A. Ignore reproductive goals until after induction. B. Select agents after integrating disease activity, fetal risk, maternal risk, and multidisciplinary obstetric care. C. Stop hydroxychloroquine routinely. D. Use mycophenolate throughout pregnancy.
Answer: B. Treatment must be pregnancy-compatible and coordinated.