Management of Stage 3a CKD with GFR 43 mL/min/1.73 m²
For a patient with Stage 3a CKD (GFR 43 mL/min/1.73 m²) and elevated BUN/creatinine ratio, initiate blood pressure control targeting ≤130/80 mmHg using an ACE inhibitor or ARB, start statin therapy, assess for proteinuria to guide treatment intensity, and monitor eGFR every 3 months to determine progression trajectory. 1, 2
Blood Pressure Management
Target blood pressure ≤130/80 mmHg using ACE inhibitors or ARBs as first-line agents, particularly if any degree of albuminuria is present. 1, 2
The 2017 ACC/AHA guidelines based on SPRINT trial data (which included 28% of patients with Stage 3-4 CKD) demonstrated that intensive BP control reduced cardiovascular events and all-cause mortality without increasing kidney-specific adverse outcomes. 1
ACE inhibitors or ARBs are preferred because they reduce intraglomerular pressure and proteinuria; expect serum creatinine to increase up to 30% after initiation, which reflects hemodynamic changes rather than kidney injury. 1
Avoid combining ACE inhibitors with ARBs as this increases risk of hyperkalemia, hypotension, and acute kidney injury without additional benefit. 1
Add a thiazide or thiazide-like diuretic as second-line therapy; most patients require combination therapy to achieve BP targets. 1
Proteinuria Assessment and Management
Measure urine albumin-to-creatinine ratio (ACR) immediately to risk-stratify and guide treatment intensity. 1, 3
If ACR ≥30 mg/g (moderately increased albuminuria), this significantly increases risk for both CKD progression and cardiovascular events, mandating aggressive BP control and RAS blockade. 1
If ACR ≥300 mg/g or protein excretion >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol), refer to nephrology as kidney biopsy and immunosuppressive therapy may be indicated. 1
Cardiovascular Risk Reduction
Initiate statin therapy regardless of baseline LDL cholesterol as Stage 3 CKD confers high cardiovascular risk equivalent to established coronary disease. 1
The majority of patients with Stage 3 CKD die from cardiovascular causes rather than progressing to end-stage renal disease, making cardiovascular risk reduction the primary mortality benefit. 1
Calculate 10-year ASCVD risk, though most patients with CKD automatically qualify as high-risk (≥10%) requiring aggressive risk factor modification. 1
Monitoring Strategy
Monitor serum creatinine and calculate eGFR every 3 months to establish renal function trajectory, which is more important than single eGFR values for predicting outcomes. 2, 4
A decline in eGFR >3 mL/min/1.73 m²/year indicates rapid progression requiring closer monitoring and potential nephrology referral. 4
The elevated BUN/creatinine ratio suggests either prerenal azotemia (volume depletion, heart failure, excessive diuresis) or increased protein catabolism; assess volume status and cardiac function. 1, 2
Monitor serum potassium, bicarbonate, calcium, phosphate, PTH, and hemoglobin to detect CKD complications. 3
Nephrology Referral Criteria
Refer to nephrology if any of the following occur: 1
- eGFR <30 mL/min/1.73 m² (Stage 3b progressing toward Stage 4)
- Proteinuria >1 g/day (ACR ≥60 mg/mmol)
- eGFR decline >20% over 3-6 months after excluding reversible causes
- eGFR decline >3 mL/min/1.73 m²/year
- Refractory hypertension requiring ≥4 antihypertensive agents
- Persistent hyperkalemia or other severe electrolyte abnormalities
For stable Stage 3a CKD with slow or no progression, formal nephrology referral may not be necessary; specialist advice can guide primary care management. 1
Medication Management
Review and discontinue nephrotoxic medications: 3
- Stop NSAIDs permanently
- Avoid aminoglycosides and other nephrotoxic antibiotics when alternatives exist
- Use caution with contrast agents; ensure adequate hydration before procedures
- Temporarily hold ACE inhibitors/ARBs during acute illness with volume depletion
Adjust medication dosing for reduced GFR, particularly antibiotics, oral hypoglycemics (metformin contraindicated if eGFR <30), and other renally-cleared drugs. 3
Avoid direct renin inhibitors combined with ACE inhibitors or ARBs due to increased adverse events without benefit. 1
Diabetes Management (if present)
Target HbA1c <7% to slow CKD progression, though avoid aggressive lowering causing hypoglycemia. 1
Consider SGLT2 inhibitors as they provide additional renoprotection beyond glycemic control in diabetic CKD. 5
Monitor HbA1c every 3 months until stable, then every 6 months. 1
Common Pitfalls to Avoid
Do not withhold ACE inhibitors/ARBs due to mild creatinine elevation (up to 30%) after initiation; this hemodynamic effect is expected and protective long-term. 1
Do not target systolic BP <120 mmHg if it results in diastolic BP <70 mmHg, as this may compromise coronary and renal perfusion, especially with concurrent low cardiac output. 2
Do not assume "normal" serum creatinine excludes significant CKD; a creatinine of 1.1 mg/dL in an elderly woman may represent GFR <60 mL/min/1.73 m². 6
Do not delay diagnosis or treatment; each year of diagnostic delay increases risk of progression to Stage 4/5 CKD by 40% and kidney failure by 63%. 7