What is the management plan for a patient with a Glomerular Filtration Rate (GFR) of 39 and no proteinuria, indicating Impaired Renal Function?

Management of GFR 39 with No Proteinuria

A patient with GFR 39 mL/min/1.73 m² and no proteinuria (Stage 3b CKD) should be managed primarily in primary care with aggressive cardiovascular risk reduction, strict blood pressure control, and nephrology referral only if there is evidence of progression, unclear diagnosis, or development of complications. 1

Nephrology Referral Decision

Referral to nephrology is NOT automatically required at this GFR level if the kidney function is stable and the diagnosis is clear. 1

• The Canadian Society of Nephrology clarifies that while GFR <30 mL/min/1.73 m² is the threshold for nephrology referral, it is reasonable NOT to refer patients whose GFR is below this threshold if the GFR is stable, the diagnosis is relatively clear, or if very advanced age or comorbidity indicates short life expectancy. 1

• Refer to nephrology if any of the following develop: 1

  • Abrupt sustained decrease in eGFR >20% after excluding reversible causes
  • Development of significant proteinuria (>1 g/day or ACR ≥60 mg/mmol)
  • Rapid progression of CKD
  • Unexplained or unexpected change in GFR, especially in non-elderly patients
  • Persistent electrolyte abnormalities
  • Hypertension refractory to 4 or more antihypertensive agents
  • Uncertainty about diagnosis

Primary Management Focus: Cardiovascular Risk Reduction

The vast majority of patients with Stage 3 CKD do not progress to end-stage renal disease but die mainly from cardiovascular causes. 1

• Patients with CKD are 5-10 times more likely to die prematurely (primarily from cardiovascular disease) than to progress to end-stage kidney disease. 2
• Primary care intervention for cardiovascular risk reduction should be strongly prioritized. 1

Blood Pressure Management

Target blood pressure <140/90 mmHg in the absence of proteinuria. 1

• Since this patient has no proteinuria, the more aggressive target of <130/80 mmHg (recommended for proteinuria >1000 mg/day) is not necessary. 1
• ACE inhibitors or ARBs are first-line agents even without proteinuria for their renoprotective effects, though calcium channel blockers are also appropriate. 1, 3, 4
• The effectiveness of RAAS blockade is reduced in patients on high-salt diets, so dietary sodium restriction is essential. 1

Monitoring Strategy

Monitor GFR trajectory rather than focusing solely on the current GFR value. 5

• Assess eGFR and proteinuria at least annually. 1
• A renal function trajectory showing decline >3 mL/min/1.73 m²/year warrants closer follow-up and may indicate need for nephrology referral. 5
• Many patients with CKD Stage 3-4 have stable renal function for years and never require renal replacement therapy. 5
• Monitor for an abrupt sustained decrease in eGFR >20%, which would trigger nephrology referral after excluding reversible causes. 1

Assessment for CKD Complications

Begin screening for complications of decreased GFR once GFR declines below 60 mL/min/1.73 m². 1

At GFR 39, evaluate and manage: 1, 6

• Anemia (reduced erythropoietin production)
• Mineral bone disease (disturbed vitamin D, calcium, and phosphate metabolism)
• Metabolic acidosis (consider oral bicarbonate if serum bicarbonate <22 mmol/L, though balance against sodium load)
• Nutritional status (risk of malnutrition)
• Electrolyte abnormalities (particularly potassium)

Dietary Interventions

Restrict dietary sodium to <2 grams per day to improve blood pressure control and slow GFR decline. 1

• Protein intake: At GFR <60 mL/min/1.73 m² without proteinuria, target 0.8 g/kg/day, but avoid <0.6 g/kg/day due to malnutrition risk. 1
• Emphasize plant-based protein sources. 1
• Caloric intake: Target 30-35 kcal/kg/day at this GFR level. 1

Avoid Nephrotoxic Exposures

Patients with CKD at GFR 39 are particularly susceptible to acute kidney injury from nephrotoxins. 1

• Avoid or use with extreme caution: 1
  • NSAIDs (non-steroidal anti-inflammatory drugs)
  • Aminoglycosides
  • Amphotericin B
  • Radiocontrast agents (use adequate hydration protocols when unavoidable)

Additional Cardiovascular Risk Management

Aggressively manage all cardiovascular risk factors: 1, 6

• Tight glycemic control if diabetic (HbA1c targets per diabetes guidelines)
• Lipid management with statins
• Smoking cessation
• Weight management to achieve normal BMI

Common Pitfalls to Avoid

• Do not automatically refer to nephrology based solely on GFR <40 if function is stable and diagnosis is clear. 1
• Do not overlook cardiovascular risk reduction in favor of focusing only on kidney-specific interventions—cardiovascular death is the primary risk. 1, 2
• Do not prescribe protein restriction <0.6 g/kg/day due to malnutrition risk. 1
• Do not ignore the importance of sodium restriction—RAAS blockade loses efficacy with high salt intake. 1
• Do not delay screening for CKD complications (anemia, bone disease, acidosis) until nephrology referral. 1, 6