What are the differences in treatment approaches for Acute Kidney Injury (AKI) vs Chronic Kidney Disease (CKD)?

Treatment Approaches: AKI vs CKD

The fundamental difference in treatment approaches is that AKI management focuses on identifying and reversing the acute cause within 7 days while preventing progression, whereas CKD management emphasizes long-term strategies to slow progression and manage complications over months to years. 1, 2

Temporal Framework and Definitions

• AKI is defined as kidney dysfunction occurring over less than 7 days, characterized by rapid increases in serum creatinine or decreased urine output 1, 3
• CKD is defined as kidney dysfunction persisting for more than 3 months 1, 3
• Acute Kidney Disease (AKD) bridges these conditions, representing dysfunction present for 7 days to 3 months 1
• AKI and CKD exist on a continuum where initial injury can lead to persistent damage and eventual CKD 1

AKI-Specific Management Priorities

Immediate Assessment and Intervention (First 48-72 Hours)

When AKI is diagnosed, immediately reassess the underlying etiology and consider correction of reversible causes. 1

• Discontinue all nephrotoxic agents when possible—this is the highest priority intervention 1, 2
• Ensure adequate volume status and perfusion pressure through fluid resuscitation and vasopressor support as needed 1, 2
• Monitor serum creatinine and urine output closely using KDIGO staging criteria rather than eGFR equations 1, 2, 4
• Evaluate urine sediment, proteinuria, and consider biomarker assessment to identify specific causes 1

Critical Pitfall in AKI Assessment

Never use MDRD or CKD-EPI equations to estimate GFR in AKI patients—these require steady-state creatinine conditions that do not exist in acute settings. 1, 4 Instead, use serial creatinine measurements and KDIGO staging, or timed urine creatinine clearance if precise GFR estimation is necessary 1, 4

Persistent AKI Management (Beyond 48 Hours)

When AKI persists beyond 48 hours, escalate your approach: 1

• Re-evaluate hemodynamic and volume status to ensure adequate kidney perfusion 1
• Identify complications requiring intervention: fluid overload, acidosis, hyperkalemia 1
• Consider nephrology consultation if etiology remains unclear or subspecialist care is needed 1
• Consider kidney biopsy for unresolving AKI/AKD to identify underlying glomerular or interstitial disease 1, 3

Renal Replacement Therapy Considerations

• Initiation of RRT in AKI focuses on refractory complications (hyperkalemia, acidosis, fluid overload) rather than early prophylactic use 1, 5, 6
• Intermittent hemodialysis is preferred in most disaster/resource-limited settings due to rapid potassium clearance and ability to treat multiple patients per machine 1
• In hypercatabolic states (e.g., crush injury), one or more dialysis treatments per day may be required for potassium control 1

CKD-Specific Management Priorities

Long-Term Strategic Approach

CKD management shifts from acute intervention to chronic disease modification and complication prevention. 2

• Implement cause-specific classification using the CGA system (Cause, GFR, Albuminuria) to guide targeted therapy 1, 3, 2
• Initiate ACE inhibitor or ARB therapy for patients with hypertension and proteinuria to slow progression 2
• Avoid dual RAAS blockade—this increases hyperkalemia and AKI risk without additional benefit 2
• Adjust medication dosing based on stable GFR estimates using validated CKD equations (MDRD, CKD-EPI) 1, 2

Monitoring and Follow-Up

• Use eGFR equations (MDRD, CKD-EPI) for longitudinal monitoring—these are validated for stable CKD but not AKI 1, 4
• Monitor for CKD progression with serial GFR and albuminuria measurements 1, 2
• Screen for CKD complications: anemia, bone mineral disease, cardiovascular disease 2

The Bidirectional Relationship: Critical Clinical Implications

AKI survivors are at high risk for developing CKD, and pre-existing CKD dramatically increases AKI risk—this bidirectional relationship demands long-term follow-up even after apparent AKI recovery. 7, 8

Risk Factors for AKI-to-CKD Progression

Patients at highest risk include those with: 7

• Advanced age
• Diabetes mellitus
• Decreased baseline GFR
• Severe AKI (Stage 2-3)
• Low serum albumin

Transition Management (AKI → AKD → CKD)

As kidney function stabilizes after AKI (typically after 7 days), transition from AKI-based staging to GFR-based categories. 1, 2

• Between 7 days and 3 months, the patient has AKD—continue monitoring for recovery versus progression 1
• After 3 months without recovery, reclassify as CKD and implement long-term CKD management strategies 1, 3, 2
• Medication dosing must be reassessed during this transition as kidney function changes 1, 2

Common Pitfalls to Avoid

1. Using eGFR equations in AKI: MDRD and CKD-EPI are invalid during dynamic creatinine changes 1, 4
2. Failing to provide long-term follow-up after AKI: Even patients with apparent complete recovery remain at risk for CKD 7, 8
3. Overlooking medication dose adjustments: Both during AKI-to-CKD transition and when initiating dialysis 1, 2
4. Assuming AKI and CKD are distinct entities: They represent a continuum requiring integrated management 8
5. Delaying nephrology consultation: Consider early involvement for persistent AKI (>48 hours) or unclear etiology 1

Algorithmic Decision Framework

For new kidney dysfunction:

1. Determine timeline: <7 days = AKI; 7 days-3 months = AKD; >3 months = CKD 1
2. If AKI: Stop nephrotoxins → Optimize hemodynamics → Monitor with serial creatinine (not eGFR) → Reassess at 48 hours 1, 2, 4
3. If persistent beyond 48 hours: Re-evaluate etiology → Consider biopsy → Nephrology consultation 1
4. If AKD: Continue monitoring → Prepare for either recovery or CKD transition 1
5. If CKD or AKI→CKD: Implement CGA classification → Start RAAS blockade if indicated → Adjust medications → Long-term nephrology follow-up 1, 3, 2