What are the guidelines for treating common kidney illnesses, such as chronic kidney disease (CKD) and acute kidney injury (AKI)?

Guidelines for Treating Common Kidney Illnesses

The management of common kidney illnesses such as chronic kidney disease (CKD) and acute kidney injury (AKI) requires systematic evaluation of kidney function, identification of underlying causes, and implementation of evidence-based interventions to slow disease progression and prevent complications. 1

Definition and Classification

Chronic Kidney Disease (CKD)

CKD is defined as abnormalities in kidney structure or function persisting for >3 months, characterized by:

• GFR <60 mL/min/1.73 m² and/or
• Markers of kidney damage (albuminuria, urine sediment abnormalities, electrolyte disorders due to tubular disorders, abnormalities on histology, structural abnormalities on imaging, or history of kidney transplantation) 1

CKD is classified based on:

1. Cause - Identify underlying etiology
2. GFR category (G1-G5)
3. Albuminuria category (A1-A3) 1

Acute Kidney Injury (AKI)

AKI is defined as an abrupt decrease in kidney function occurring over hours to days (<7 days), with criteria including:

• Increase in serum creatinine by ≥0.3 mg/dL within 48 hours
• Increase in serum creatinine to ≥1.5 times baseline within 7 days
• Urine volume <0.5 mL/kg/hour for 6 hours 1, 2

Acute Kidney Disease (AKD)

AKD represents kidney damage or decreased function persisting between 7 days and 3 months after an AKI event 1, 2

Diagnostic Approach

Initial Assessment

1. Test for both GFR and albuminuria in people at risk for CKD 1
2. Estimate GFR using creatinine-based equations (eGFRcr); if available, use combined creatinine and cystatin C (eGFRcr-cys) for more accurate assessment 1
3. Assess albuminuria using urinary albumin-to-creatinine ratio (ACR) 1
4. Confirm chronicity (>3 months) through:
   • Review of past GFR measurements
   • Review of past albuminuria/proteinuria measurements
   • Imaging findings (reduced kidney size, cortical thinning)
   • Kidney pathology (fibrosis, atrophy)
   • Medical history 1

Risk Stratification

• Combine GFR and albuminuria categories to determine risk for CKD outcomes 1
• Consider additional risk factors: cause of CKD, comorbidities, rate of GFR decline 1

Management of CKD

Blood Pressure Control

• Target blood pressure:
  • For patients with albuminuria <30 mg/24h: ≤140/90 mmHg 1
  • For patients with albuminuria ≥30 mg/24h: ≤130/80 mmHg 1
• First-line agents: ACE inhibitors or ARBs for patients with albuminuria >300 mg/24h 1

Proteinuria Reduction

• Use ACE inhibitors or ARBs in both diabetic and non-diabetic adults with CKD and urine albumin excretion >300 mg/24h 1
• Monitor kidney function and potassium levels when initiating these medications 3

Glycemic Control

• Target HbA1c: approximately 7% for patients with diabetes 1
• Medication considerations:
  • Adjust dosing of oral hypoglycemic agents based on kidney function
  • Metformin is contraindicated when eGFR <30 mL/min/1.73 m² and not recommended for initiation when eGFR is 30-45 mL/min/1.73 m² 4

Lifestyle Modifications

• Reduced sodium intake (<2g/day)
• Healthy body mass index (20-25 kg/m²)
• Smoking cessation
• Regular exercise (30 minutes, 5 times weekly) 1

Monitoring and Management of Complications

• Regular monitoring for:
  • Hyperkalemia
  • Metabolic acidosis
  • Hyperphosphatemia
  • Vitamin D deficiency
  • Secondary hyperparathyroidism
  • Anemia 5

Management of AKI

Prevention and Early Management

• Identify patients at risk for AKI, particularly those with CKD 1
• Maintain optimal fluid status (euvolemia) 2
• Review and adjust medications that can cause or worsen kidney injury 2
• Monitor kidney function with serum creatinine and electrolytes at least every 48 hours in high-risk patients 2

Specific Interventions

• Fluid management: Use isotonic crystalloids rather than colloids for volume expansion 2
• Medication management: Avoid nephrotoxins (NSAIDs, aminoglycosides) and adjust medication dosages according to kidney function 2, 3
• Consider renal replacement therapy for severe hyperkalemia, metabolic acidosis, volume overload, or uremic symptoms 2

Follow-up After AKI

• Schedule follow-up for all AKI survivors at 3 months to assess for CKD development 2
• Intensity of follow-up should be based on AKI severity and duration:
  • Mild, resolved AKI: Primary care follow-up
  • Prolonged AKI: Laboratory tests within days of discharge
  • AKI stage 2-3: Nephrology follow-up within 1-2 weeks 2

Referral to Nephrology

Indications for Referral

• eGFR <30 mL/min/1.73 m² 5, 6
• Severe albuminuria (>300 mg/24h) despite appropriate treatment 6
• Rapid decline in GFR (>5 mL/min/1.73 m² per year) 5
• Persistent hematuria or significant proteinuria of unclear etiology 6
• Difficult-to-manage complications (resistant hypertension, electrolyte disorders) 6
• AKI not resolving after 48 hours of appropriate therapy 2

Common Pitfalls to Avoid

• Failure to screen high-risk individuals for CKD (diabetes, hypertension, family history) 1
• Relying solely on serum creatinine without calculating eGFR 1
• Overlooking albuminuria as a marker of kidney damage 1
• Inadequate medication review in patients with reduced kidney function 2
• Failure to monitor AKI survivors for development of CKD 2
• Delayed referral to nephrology for advanced or rapidly progressing CKD 6

By following these guidelines for evaluation and management, healthcare providers can effectively diagnose and treat common kidney illnesses, potentially slowing disease progression and improving patient outcomes.