What are the diagnostic criteria and management guidelines for nephropathy?

Diagnostic Criteria and Management Guidelines for Nephropathy

Nephropathy is diagnosed based on persistent albuminuria (≥30 mg/g creatinine) and/or reduced estimated glomerular filtration rate (eGFR <60 mL/min/1.73m²) for at least 3 months, with staging determined by both parameters according to KDIGO guidelines. 1

Diagnostic Criteria

Albuminuria Assessment

• Albuminuria is categorized into three stages 1:
  • A1: Normal to mildly increased (<30 mg/g creatinine)
  • A2: Moderately increased (30-299 mg/g creatinine) - formerly called microalbuminuria
  • A3: Severely increased (≥300 mg/g creatinine) - formerly called macroalbuminuria

GFR Assessment

• GFR categories for staging 1:
  • G1: Normal or high (≥90 mL/min/1.73m²)
  • G2: Mildly decreased (60-89 mL/min/1.73m²)
  • G3a: Mildly to moderately decreased (45-59 mL/min/1.73m²)
  • G3b: Moderately to severely decreased (30-44 mL/min/1.73m²)
  • G4: Severely decreased (15-29 mL/min/1.73m²)
  • G5: Kidney failure (<15 mL/min/1.73m²)

Confirming Chronicity

• Chronicity (duration of at least 3 months) must be established through 1:
  • Review of past GFR measurements
  • Review of past albuminuria measurements
  • Imaging findings (reduced kidney size, cortical thinning)
  • Pathological findings (fibrosis, atrophy)
  • Medical history of conditions known to cause CKD

Preferred Testing Methods

• For albuminuria: Morning spot urine albumin-to-creatinine ratio (uACR) is recommended for annual screening 1
• For GFR: Creatinine-based eGFR (eGFRcr) is recommended; if available, combined creatinine and cystatin C-based eGFR (eGFRcr-cys) provides greater accuracy 1
• 24-hour urine collection should be performed when initiating or intensifying immunosuppression or when clinical status changes 1

Screening Recommendations

For Diabetic Nephropathy

• Type 1 diabetes: Begin screening 5 years after diagnosis 1, 2
• Type 2 diabetes: Begin screening at diagnosis and yearly thereafter 1, 2
• Consider earlier screening with puberty, poor metabolic control, or family history 1

For Non-Diabetic Nephropathy

• Screen patients with risk factors including 1:
  • African American race
  • Hypertension
  • Hepatitis C virus coinfection
  • HIV with CD4+ counts <200 cells/mm³ or HIV RNA >14,000 copies/mL

Management Guidelines

Blood Pressure Control

• For patients with albuminuria <30 mg/24h: Target BP ≤140/90 mmHg 1
• For patients with albuminuria ≥30 mg/24h: Target BP ≤130/80 mmHg 1
• For patients with proteinuria >1 g/24h: Target BP ≤125/75 mmHg 2

RAAS Blockade

• ACE inhibitors or ARBs are recommended for 1:
  • All patients with albuminuria >300 mg/24h (both diabetic and non-diabetic)
  • Suggested for patients with albuminuria 30-300 mg/24h

Glycemic Control

• Target HbA1c <7% to prevent development and progression of diabetic nephropathy 2

Additional Measures

• Lipid management: Target LDL cholesterol <100 mg/dL 2
• Lifestyle modifications 1:
  • Reduced sodium intake (<2 g/day)
  • Healthy BMI (20-25 kg/m²)
  • Smoking cessation
  • Regular exercise (30 minutes, 5 times weekly)

Monitoring Frequency

• If eGFR ≥60 mL/min/1.73m² and albuminuria <30 mg/g: Annual monitoring 1
• If eGFR <60 mL/min/1.73m² and/or albuminuria >30 mg/g: Monitor every 6 months 1
• After confirming albuminuria >30 mg/g on 2 of 3 tests within 3-6 months, repeat testing to evaluate treatment efficacy 1

Special Considerations

Anticoagulation in Nephrotic Syndrome

• Consider prophylactic anticoagulation when 1:
  • Serum albumin <25 g/L (measured by bromocresol green)
  • High risk of venous thromboembolism
  • Previous history of thrombosis
  • Membranous nephropathy (particularly high risk)

Infection Prevention

• Vaccinations recommended for patients with nephropathy 1:
  • Pneumococcal vaccine
  • Annual influenza vaccine
  • Herpes zoster vaccination (Shingrix)
• Consider prophylactic trimethoprim-sulfamethoxazole for patients on high-dose immunosuppression 1

Kidney Biopsy Indications

• Consider kidney biopsy when 1:
  • Rapid decline in kidney function
  • Nephrotic-range proteinuria without diabetes
  • Hematuria with proteinuria
  • Suspected systemic disease affecting kidneys
  • To guide treatment decisions when clinically appropriate

Common Pitfalls in Diagnosis

• Single abnormal eGFR or ACR measurement is insufficient for diagnosis - confirm chronicity 1
• Albuminuria may be transiently elevated due to fever, exercise, urinary tract infection, or heart failure 3
• Standard screening may miss early kidney damage before albumin excretion increases 4
• First morning urine collections may underestimate 24-hour protein excretion in orthostatic proteinuria 1
• Random spot urine collections have significant variation and are not ideal for monitoring 1