Should a repeat kidney biopsy be performed in a 45-year-old man with IgA nephropathy who has relapsed with increased serum creatinine and proteinuria while on optimal supportive therapy?

Repeat Kidney Biopsy in IgA Nephropathy with Relapse

In a 45-year-old man with IgA nephropathy who has relapsed with increased serum creatinine and proteinuria despite optimal supportive therapy, a repeat kidney biopsy should be performed to distinguish active inflammatory disease from chronic scarring, as this distinction fundamentally determines whether to escalate immunosuppression or avoid potentially toxic therapy. 1

When to Perform Repeat Biopsy in IgA Nephropathy

The KDIGO guideline explicitly recommends repeat kidney biopsy in IgAN patients with acute kidney injury (AKI) associated with macroscopic hematuria if there is no improvement after 5 days from onset of kidney function worsening. 1 While this specific scenario addresses AKI with gross hematuria, the underlying principle—that repeat biopsy guides therapeutic decisions when clinical deterioration occurs—applies directly to your patient with relapsing disease.

Key Clinical Scenarios Warranting Repeat Biopsy

• Worsening renal function during or after treatment suggests either refractory active disease (requiring alternative immunosuppression) or progressive scarring (where immunosuppression may cause harm without benefit). 1

• Persistent or worsening proteinuria after completing initial therapy requires distinguishing ongoing immune activity from irreversible glomerulosclerosis. 1

• Suspicion of histological class change or uncertainty whether rising creatinine represents disease activity versus chronicity mandates repeat biopsy. 1

What Repeat Biopsy Reveals in IgA Nephropathy

Reversible vs. Irreversible Lesions

Research demonstrates that mesangial proliferation, endocapillary proliferation, cellular crescents, and interstitial inflammation are substantially reversible with appropriate treatment, while globally sclerotic glomeruli and advanced interstitial fibrosis represent irreversible damage. 2 In one study of 35 IgAN patients who underwent repeat biopsy after treatment:

• Mesangial proliferation scores decreased from 2.49 to 0.91 (p<0.001). 2
• All acute inflammatory lesions (endocapillary proliferation, tuft necrosis, cellular crescents) resolved completely. 2
• Interstitial fibrosis/edema decreased from 21.4% to 9.6% (p<0.01). 2
• Eight patients showed complete disappearance of IgA deposits. 2

This evidence proves that even established IgAN can regress histologically, but only if active inflammatory lesions—not chronic scarring—predominate. 2

Activity vs. Chronicity Assessment

Repeat biopsy quantifies the activity index (mesangial proliferation, endocapillary proliferation, crescents) versus chronicity index (glomerulosclerosis, interstitial fibrosis/tubular atrophy). 3 One study showed that while proteinuria decreased dramatically with immunosuppression (from 2.53 to 0.26 g/day), the activity index decreased from 3.18 to 2.47 (p<0.05), but the chronicity index remained unchanged (2.59 vs. 2.76). 3 This demonstrates that clinical remission (proteinuria reduction) does not guarantee histological remission—active lesions may persist despite apparent clinical improvement. 3

Treatment Implications Based on Repeat Biopsy Findings

If Active Lesions Predominate

Patients with persistent active inflammatory lesions on repeat biopsy should receive escalated or alternative immunosuppressive therapy. 1 The KDIGO guideline recommends:

• For crescentic IgAN (>50% crescents with rapidly progressive renal deterioration), treat with steroids plus cyclophosphamide analogous to ANCA vasculitis. 1
• For persistent proteinuria ≥1 g/day despite 3-6 months of optimized supportive care and eGFR >50 ml/min/1.73m², administer a 6-month course of corticosteroid therapy. 1

If Chronic Scarring Predominates

If repeat biopsy shows predominantly chronic changes (>50% glomerulosclerosis, extensive interstitial fibrosis/tubular atrophy >50%), avoid immunosuppressive therapy. 1 The guideline explicitly states: "We suggest not using immunosuppressive therapy in patients with eGFR <30 ml/min/1.73m² unless there is crescentic IgAN with rapidly deteriorating kidney function." 1

This recommendation exists because immunosuppression carries significant toxicity (infection, malignancy, bone disease) without benefit when irreversible scarring drives renal dysfunction. 1

Practical Algorithm for Your Patient

Step 1: Quantify Current Disease Activity

• Measure spot urine protein-to-creatinine ratio (UPCR) to confirm relapse severity. 4
• Document blood pressure control (<120/70 mm Hg target per 2025 KDIGO). 5
• Verify maximal renin-angiotensin system blockade (ACE inhibitor or ARB titrated to maximum tolerated dose). 1, 4

Step 2: Perform Repeat Kidney Biopsy

Proceed with repeat biopsy without delay if:

• Serum creatinine has increased >30% over 6-12 months. 4
• Proteinuria exceeds 1 g/day despite optimal supportive therapy for 3-6 months. 1
• There is uncertainty whether deterioration represents active disease or chronic scarring. 1

Step 3: Interpret Biopsy Results Using MEST-C Score

The 2025 KDIGO guideline mandates scoring repeat biopsies using the MEST-C classification:

• M (mesangial hypercellularity): >50% of glomeruli with >4 mesangial cells in any mesangial area. 5
• E (endocapillary hypercellularity): presence indicates active inflammation. 5
• S (segmental glomerulosclerosis): indicates chronic damage. 5
• T (tubular atrophy/interstitial fibrosis): T0 (<25%), T1 (25-50%), T2 (>50%). 5
• C (crescents): cellular crescents indicate active disease; fibrous crescents indicate chronicity. 5

Step 4: Treatment Decision Based on Histology

If E1 (endocapillary proliferation present) or cellular crescents (C1/C2) with T0-T1 (limited fibrosis):

• Initiate or escalate immunosuppression with corticosteroids. 1
• Consider combination therapy targeting multiple pathogenic pathways per 2025 KDIGO. 5
• If crescents involve >50% of glomeruli, treat with cyclophosphamide plus steroids. 1

If E0, M0, with T2 (>50% interstitial fibrosis) and predominantly global glomerulosclerosis:

• Avoid immunosuppression. 1
• Focus on nephroprotective strategies: SGLT2 inhibitors, strict blood pressure control, dietary sodium restriction <2 g/day. 5, 4
• Prepare for renal replacement therapy if eGFR <20 ml/min/1.73m². 1

Common Pitfalls to Avoid

Pitfall 1: Assuming Clinical Remission Equals Histological Remission

Proteinuria reduction does not guarantee resolution of active inflammatory lesions. 3 One study found that despite achieving clinical remission (proteinuria <0.3 g/day), repeat biopsy still showed active lesions with an activity index of 2.47. 3 This suggests that immunosuppression should not be withdrawn based solely on proteinuria reduction—repeat biopsy may be necessary before stopping therapy. 3

Pitfall 2: Delaying Biopsy in Patients with "Slow" Progression

The 2025 KDIGO guideline emphasizes that even proteinuria ≥0.5 g/day (not just ≥1 g/day) carries elevated risk for kidney failure. 6 A recent US cohort study showed that compared to UPCR <0.5 g/g, time-averaged UPCR of 0.5-<1 g/g carried a hazard ratio of 5.4 for ≥50% eGFR decline/kidney failure. 6 Do not wait for dramatic deterioration—biopsy when proteinuria persists at ≥0.5 g/day despite optimal therapy. 5, 6

Pitfall 3: Attributing All Renal Dysfunction to IgAN

Repeat biopsy may reveal superimposed acute interstitial nephritis (AIN) from medications (proton pump inhibitors, antibiotics, diuretics), calcineurin inhibitor toxicity, or other glomerular diseases. 7 One case report described a patient with membranous nephropathy whose creatinine worsened during steroid taper; repeat biopsy revealed AIN from pantoprazole, trimethoprim-sulfamethoxazole, and furosemide. 7 Always review medications before attributing worsening renal function solely to IgAN progression. 7

Evidence from Lupus Nephritis Applies to IgAN

Although the strongest guideline recommendations for repeat biopsy come from the lupus nephritis literature, the same principles apply to IgAN. 1, 8 KDIGO states: "In patients with worsening serum creatinine and/or proteinuria after completing one of the initial treatment regimens, consider performing a repeat kidney biopsy to distinguish active lupus nephritis from scarring." 1 The KDOQI commentary emphasizes that repeated biopsies play an important role in guiding treatment decisions because worsening kidney function and persistent proteinuria may occur in the absence of inflammatory activity and should not be treated with immunosuppressive therapies. 8

Duration of Follow-Up After Repeat Biopsy

If repeat biopsy shows active lesions and immunosuppression is initiated, plan for long-term maintenance therapy. 5 The 2025 KDIGO guideline notes that "maintenance immunologic treatment, as used in most other immune-mediated glomerular diseases, may be required" because "when some medications are stopped, proteinuria quickly returns." 5 This represents a paradigm shift from older approaches that limited immunosuppression duration in IgAN. 5