How is chronic nephritis diagnosed?

Diagnosis of Chronic Nephritis

Chronic nephritis is definitively diagnosed by renal biopsy showing chronic glomerular inflammation with interstitial fibrosis, tubular atrophy, and glomerulosclerosis, combined with clinical evidence of kidney disease persisting for at least 3 months. 1

Establishing Chronicity (≥3 Months Duration)

The diagnosis requires proof that kidney disease has been present for at least 3 months, which can be established through: 1

• Review of past GFR measurements showing persistently reduced kidney function 1
• Serial urinalysis results demonstrating ongoing proteinuria, hematuria, or abnormal sediment 1
• Imaging findings including reduced kidney size (<9-10 cm), cortical thinning (<0.5 cm), loss of corticomedullary differentiation, or increased echogenicity 1, 2
• Repeat measurements at the 3-month point if prior data unavailable 1

Critical pitfall: Do not assume chronicity from a single abnormal test, as this could represent acute kidney injury or acute kidney disease rather than chronic nephritis. 1

Clinical Screening Criteria

Initial evaluation should identify: 3

• Proteinuria ≥0.5 g/24 hours (or spot urine protein-to-creatinine ratio >0.5) 1, 3
• Active urinary sediment: >5 RBC/hpf, >5 WBC/hpf (without infection), or cellular casts (RBC or WBC casts) 1, 3
• Elevated serum creatinine with reduced estimated GFR 3
• Hypertension (present in approximately 70% of patients with elevated creatinine) 2

Renal Biopsy: The Definitive Diagnostic Test

Biopsy should not be delayed when clinical criteria are met, as it determines the specific histological diagnosis that dictates treatment strategy. 3

Absolute Indications for Biopsy:

• Proteinuria ≥1.0 g/24 hours alone 3
• Proteinuria ≥0.5 g/24 hours with hematuria or cellular casts 3
• Unexplained kidney dysfunction with clinical suspicion of glomerulonephritis 1, 3

Timing:

Perform biopsy within the first month after disease onset, preferably before starting immunosuppressive treatment. 3

Technical Requirements:

• Minimum 10 glomeruli for adequate light microscopy evaluation 3
• Essential stains: H&E, PAS, Masson's trichrome, and silver stain 3
• Immunofluorescence panel: IgG, C3, IgA, IgM, C1q, κ and λ light chains 1, 3
• Electron microscopy for ultrastructural evaluation 1, 3

Histological Features of Chronic Nephritis

The biopsy will demonstrate: 1

• Glomerulosclerosis (focal or global) with percentage quantified 1
• Interstitial fibrosis and tubular atrophy (IFTA) graded as mild, moderate, or severe 1
• Vascular changes: arteriosclerosis and arteriolosclerosis 1
• Pattern of injury: mesangial proliferative, membranoproliferative, crescentic, or sclerosing patterns 1
• Immune deposits on immunofluorescence indicating specific disease type (IgA, IgG, C3, etc.) 1

Supportive Serological Testing

While serological tests provide supportive information, they do not replace biopsy. Consider based on clinical context: 3

• Complement levels (C3, C4) for immune complex diseases 3
• ANA and anti-dsDNA for lupus nephritis 1, 3
• ANCA panel (MPO, PR3) for vasculitis 1, 3
• Anti-GBM antibodies for Goodpasture syndrome 1, 3
• Serum and urine protein electrophoresis for monoclonal gammopathies 1, 3

Imaging: Limited Role

Imaging is not part of the standard nephritis diagnostic workup and does not diagnose glomerulonephritis. 3

However, ultrasound may be useful for: 1, 2

• Assessing kidney size and cortical thickness to establish chronicity 1, 2
• Pre-biopsy anatomical evaluation 1
• Excluding obstruction or structural abnormalities 1

CT and MRI are not beneficial for diagnosing glomerulonephritis. 1, 3

Distinguishing Chronic from Acute Interstitial Nephritis

Histological features favoring chronicity: 4, 5

• Tubular atrophy (highest predictive value) 4
• Interstitial granuloma formation 4
• Pronounced interstitial cell infiltration 4
• Imaging showing renal shrinkage 4

Clinical features suggesting chronic course: 4

• Subacute symptoms rather than oliguria/anuria 4
• Prolonged drug exposure (>1 month) before diagnosis 4
• Chronic analgesic or NSAID use 4

Classification and Treatment Implications

The specific histological diagnosis determines treatment strategy: 1, 3

• Class I-II (minimal/mesangial): Generally no immunosuppression required 1
• Class III-IV (proliferative): Aggressive therapy with glucocorticoids and immunosuppressive agents 1
• Class V (membranous): Approach varies based on whether pure or mixed with proliferative disease 1
• Class VI (sclerotic, ≥90% glomeruli): Preparation for renal replacement therapy rather than immunosuppression 1

The histological classification, not clinical presentation alone, guides mechanism-based treatment approaches. 1, 3