What is the role of staging in the management of kidney disease?

The Role of Staging in the Management of Kidney Disease

Staging in kidney disease is critical for guiding prognostic and management recommendations, as more severe stages portend worse outcomes and require more intensive interventions. 1

Staging Systems in Kidney Disease

Chronic Kidney Disease (CKD) Staging

• CKD is classified using a comprehensive approach that includes:

  • GFR Categories (G1-G5): Based on level of kidney function
  • Albuminuria Categories (A1-A3): Reflecting kidney damage
  • Cause of Disease: Identifying underlying etiology 1, 2

• This staging system helps identify approximately 11% of the U.S. adult population (20 million persons) who have CKD, with earlier stages being far more prevalent than kidney failure 1

Acute Kidney Injury (AKI) Staging

• Based on relative changes in serum creatinine or urine output
• Three stages of severity:
  • Stage 1: Increase ≥0.3 mg/dL or 1.5-1.9× baseline; urine output <0.5 mL/kg/h for >6h
  • Stage 2: 2.0-2.9× baseline; urine output <0.5 mL/kg/h for >12h
  • Stage 3: ≥3.0× baseline or ≥4.0 mg/dL or RRT; urine output <0.3 mL/kg/h for 24h 2

Acute Kidney Disease (AKD) Staging

• Represents a transition period between AKI and CKD (7-90 days)
• Staging is evolving, with consensus that GFR and albuminuria categories could be used in AKD without AKI or AKD following AKI 1

Clinical Applications of Kidney Disease Staging

Management Based on CKD Stage

1. Stages 1-2 (GFR ≥60 mL/min/1.73m²):

   • Focus on slowing progression
   • Identifying and managing comorbidities
   • Treatment of hypertension and proteinuria 1

2. Stage 3 (GFR 30-59 mL/min/1.73m²):

   • Evaluation and treatment of complications (anemia, malnutrition, bone disease)
   • Regular monitoring of calcium, phosphorus (every 3 months)
   • Monitoring for metabolic acidosis 1

3. Stage 4 (GFR 15-29 mL/min/1.73m²):

   • Preparation for kidney replacement therapy
   • More intensive monitoring of metabolic parameters
   • Correction of metabolic acidosis to serum bicarbonate ≥22 mmol/L 1

4. Stage 5 (GFR <15 mL/min/1.73m²):

   • Initiation of dialysis or transplantation when uremic symptoms develop
   • Management of complications of kidney failure 1

Management Based on AKI Stage

• More severe AKI stages require more intensive monitoring and management
• Stage 3 AKI patients require earlier post-discharge follow-up due to higher risk of CKD progression 1
• All AKI survivors should have follow-up at 3 months to assess for CKD development 2

Clinical Impact of Staging

1. Risk Stratification:

   • Staging helps identify patients at highest risk for progression to kidney failure
   • Patients with GFR <30 mL/min/1.73m² or albuminuria ≥300 mg/24h require prompt nephrology referral 3

2. Treatment Decisions:

   • Blood pressure targets: ≤140/90 mmHg for patients with albuminuria <30 mg/24h; ≤130/80 mmHg for albuminuria ≥30 mg/24h 2
   • Medication selection: ACE inhibitors or ARBs for patients with albuminuria >300 mg/24h 2
   • SGLT2 inhibitors are now recommended alongside RAAS inhibitors for kidney protection 4

3. Monitoring Frequency:

   • More advanced stages require more frequent monitoring of kidney function, electrolytes, and complications
   • Stage 4-5 CKD: monitoring calcium, phosphorus every 3 months; iPTH at least once 1

Challenges and Controversies in Kidney Disease Staging

1. Limitations of Current Staging Systems:

   • Stages 1 and 2 CKD are difficult to determine using standard MDRD estimation of GFR 5
   • The clinical significance of early stages without other risk factors is unclear 5

2. Age Considerations:

   • Most patients with stage 3 CKD are elderly and will die before reaching ESRD 5
   • Age should be considered as a modifying factor, especially in moderate kidney impairment 5

3. Transition Between AKI and CKD:

   • The transition from AKI-based management to CKD-based management should occur before 90 days 1
   • When GFR is changing rapidly, measured GFR rather than estimated GFR should be considered 1

Best Practices for Implementing Staging in Clinical Care

• Use staging to guide frequency of monitoring and intensity of interventions
• Consider both GFR and albuminuria when assessing risk and planning management
• Recognize that staging should drive clinical action plans, including referral decisions
• For patients with AKI, ensure appropriate follow-up based on severity of injury
• For CKD patients, implement stage-appropriate interventions to slow progression and manage complications

By effectively utilizing kidney disease staging systems, clinicians can optimize patient outcomes through timely interventions, appropriate monitoring, and early specialist referral when indicated.