How is impaired renal function managed?

Management of Impaired Renal Function

The management of impaired renal function requires a comprehensive approach focused on identifying the cause, slowing progression, and treating complications through lifestyle modifications, medication adjustments, and appropriate referrals based on CKD staging and albuminuria levels.

Assessment and Classification

Chronic kidney disease (CKD) is defined as kidney damage or glomerular filtration rate (GFR) <60 mL/min/1.73 m² for ≥3 months, regardless of cause 1, 2. Proper assessment includes:

• Measurement of both GFR and albuminuria to accurately classify CKD

• Classification based on GFR categories:

  • G1: ≥90 mL/min/1.73 m²
  • G2: 60-89 mL/min/1.73 m²
  • G3a: 45-59 mL/min/1.73 m²
  • G3b: 30-44 mL/min/1.73 m²
  • G4: 15-29 mL/min/1.73 m²
  • G5: <15 mL/min/1.73 m² or dialysis

• Classification based on albuminuria categories:

  • A1: <30 mg/g
  • A2: 30-300 mg/g
  • A3: >300 mg/g

Blood Pressure Management

Blood pressure control is critical in preventing CKD progression:

• For patients with albuminuria <30 mg/24 hours: target BP ≤140/90 mmHg 1
• For patients with albuminuria ≥30 mg/24 hours: target BP ≤130/80 mmHg 1
• First-line therapy includes ACE inhibitors or ARBs for patients with albuminuria and hypertension 2
• Dihydropyridine calcium channel blockers and/or diuretics may be added if needed to achieve BP targets 2

Important Considerations with ACE Inhibitors/ARBs:

• Monitor serum creatinine and potassium levels when initiating therapy 3
• Do not discontinue for minor increases in serum creatinine (≤30%) in the absence of volume depletion 2
• Caution in patients with bilateral renal artery stenosis or severe volume depletion 3
• Contraindicated in pregnancy 3

Management of Acute Kidney Injury in CKD

For patients with acute kidney injury (AKI) and CKD:

1. Identify and treat precipitating factors:

   • Hold nephrotoxic medications (NSAIDs, aminoglycosides)
   • Discontinue diuretics, beta-blockers if appropriate 1
   • Treat infections and other precipitating causes 1

2. Volume management:

   • Administer albumin at 1 g/kg (maximum 100 g/day) for volume expansion in appropriate cases 1
   • Monitor carefully for fluid overload, especially in patients with heart failure 1

3. Consider vasoconstrictors for hepatorenal syndrome if applicable 1

4. Initiate renal replacement therapy when indicated (severe acidosis, hyperkalemia, volume overload unresponsive to diuretics, uremic symptoms) 1

Lifestyle Modifications

Diet and lifestyle modifications are essential:

• Sodium restriction to <2000 mg/day 2
• Protein intake limited to 0.8 g/kg body weight per day for stage 3 CKD 2
• Plant-based "Mediterranean-style" diet with limitations on foods rich in bioavailable potassium 2
• Physical activity: 150 minutes/week of moderate-intensity exercise, adjusted to cardiovascular tolerance 2
• Complete cessation of tobacco use 2
• Weight management: achieve and maintain optimal BMI 2

Cardiovascular Risk Management

CKD patients have increased cardiovascular risk requiring management:

• Statin therapy for adults ≥50 years with eGFR <60 ml/min/1.73 m² 2
• For diabetic patients:
  • Insulin-based therapy for type 1 diabetes
  • Metformin for type 2 diabetes if eGFR ≥30 ml/min/1.73 m²
  • SGLT2 inhibitors for type 2 diabetes with eGFR ≥20 ml/min/1.73 m² 2

Monitoring Frequency

Monitoring frequency should be based on GFR and albuminuria categories:

GFR Category	Albuminuria Category	Monitoring Frequency
G1-G2	A1	Annual
G3a	A1	1-2 times per year
G1-G2	A2	1-2 times per year
G4-G5	A1-A3	3-4 times per year
Any	A3	3-4 times per year

Nephrology Referral

Refer to nephrology in the following situations:

• eGFR <30 mL/min/1.73 m² 2
• Albuminuria ≥300 mg/24 hours 2
• Rapid decline in eGFR (>5 mL/min/1.73 m²/year) 2
• 5-year risk of end-stage renal disease >3-5% 2
• Uncertainty about etiology of kidney disease 2
• Difficult management issues 2

Special Considerations

Medication Dosing

• Impaired renal function affects drug clearance
• Dose adjustment required for many medications when eGFR <60 mL/min/1.73 m²
• Special attention needed when GFR <30 mL/min/1.73 m² 3

Contrast Studies

• Avoid iodinated contrast in AKI unless absolutely necessary 1
• For MRI, consider risk-benefit with gadolinium-based contrast agents 1
• Ultrasound contrast media are not nephrotoxic and may be preferred 1

HIV-Associated CKD

• Screen all HIV patients at diagnosis and annually for those at high risk 1
• Consider ACE inhibitors or ARBs for HIV patients with albuminuria 1

Common Pitfalls to Avoid

1. Relying solely on serum creatinine without calculating eGFR
2. Failing to measure albuminuria in CKD assessment
3. Discontinuing ACE inhibitors/ARBs due to minor increases in creatinine
4. Inadequate monitoring of electrolytes, especially potassium, in patients on RAAS blockers
5. Overlooking non-renal causes of elevated creatinine (muscle mass, diet)
6. Failing to adjust medication dosages in patients with reduced GFR
7. Not recognizing that CKD increases risk for AKI 1

By following these guidelines, clinicians can effectively manage impaired renal function to slow progression and reduce complications, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.