What is the management plan for a patient with an estimated Glomerular Filtration Rate (eGFR) of 40, indicating Impaired renal function?

Management of eGFR 40 mL/min/1.73 m²

A patient with an eGFR of 40 mL/min/1.73 m² has Stage 3b chronic kidney disease and requires immediate screening for CKD complications, medication dose adjustments, nephrotoxin avoidance, and consideration of nephrology referral if additional risk factors are present.

Classification and Risk Stratification

• An eGFR of 40 mL/min/1.73 m² indicates Stage G3b chronic kidney disease (CKD), representing moderately to severely decreased kidney function 1
• This level of renal function is associated with increased cardiovascular disease risk, CKD progression risk, and mortality 1, 2
• Complications of CKD become prevalent when eGFR falls below 60 mL/min/1.73 m², and become more common and severe as CKD progresses 1

Mandatory Screening for CKD Complications

When eGFR is <60 mL/min/1.73 m², screen for the following complications every 6-12 months for Stage 3 CKD 1:

• Blood pressure monitoring: Target <130/80 mmHg; assess at every clinical contact 1
• Volume status: Evaluate for edema through history, physical examination, and weight monitoring 1
• Electrolyte abnormalities: Measure serum sodium, potassium, chloride, and bicarbonate 1
• Metabolic acidosis: Check serum bicarbonate levels 1
• Anemia: Measure hemoglobin; if low, obtain iron studies including serum iron, iron saturation, and ferritin 1
• Mineral bone disease: Check serum calcium, phosphate, parathyroid hormone (PTH), and 25-hydroxyvitamin D 1

Medication Management

Dose Adjustments Required

• Metformin: Initiation is NOT recommended in patients with eGFR 30-45 mL/min/1.73 m² 3
• If already taking metformin when eGFR falls to 40, assess benefit-risk of continuing therapy and consider discontinuation 3
• Many antibiotics require dose reduction at this level of renal function 2
• Oral hypoglycemic agents often require dose adjustments 2
• Verify dosing of all medications, as many require adjustment when eGFR <60 mL/min/1.73 m² 1

Nephrotoxins to Avoid

• NSAIDs: Strictly avoid nonsteroidal anti-inflammatory drugs, as they reduce renal blood flow and can precipitate acute kidney injury 1, 4, 2
• Iodinated contrast: For procedures requiring contrast with eGFR 30-60 mL/min/1.73 m², discontinue metformin (if applicable) at time of procedure and restart only after confirming stable renal function 48 hours later 3
• Minimize exposure to any potentially nephrotoxic agents 1

Monitoring for Drug-Related Complications

• Patients with eGFR ≤40 mL/min/1.73 m² are at substantial risk for medication errors and adverse drug events 5
• In one study, 15% of patients with eGFR ≤40 had medication errors detected, with 88% classified as potential adverse drug events 5
• Monitor serum potassium periodically in patients receiving ACE inhibitors, ARBs, or mineralocorticoid receptor antagonists 1
• Monitor serum potassium in patients on diuretics due to risk of hypokalemia 1

Blood Pressure and Proteinuria Management

• Measure urine albumin-to-creatinine ratio (UACR) annually to assess for albuminuria 1

• If albuminuria is present (UACR ≥30 mg/g):

  • Use ACE inhibitor or ARB as first-line antihypertensive therapy 1, 4
  • Target blood pressure <130/80 mmHg 1
  • Monitor serum creatinine and potassium after initiating therapy 1
  • Accept modest increases in serum creatinine (up to 30%) as this often reflects appropriate hemodynamic changes rather than true kidney injury 4

• If no albuminuria and normal blood pressure: ACE inhibitors/ARBs are not recommended for primary prevention of CKD 1

Glycemic Control (if Diabetic)

• Target A1C of 7% to delay CKD progression 1
• Intensive glucose control has been shown to delay onset and progression of albuminuria and reduce eGFR decline in both type 1 and type 2 diabetes 1
• Many glucose-lowering medications require dose adjustment or are contraindicated at this level of renal function 1

Dietary and Lifestyle Modifications

• Dietary protein: Limit to approximately 0.8 g/kg body weight per day (the recommended daily allowance for non-dialysis CKD) 1
• Sodium restriction: Restrict to <2 g/day (<90 mmol/day) to reduce blood pressure and maximize diuretic effectiveness if needed 4
• Potassium management: May require individualization based on serum potassium levels and medication use 1
• Avoid potassium supplements and potassium-based salt substitutes, especially if on ACE inhibitors or ARBs 4

Nephrology Referral Criteria

Refer promptly to nephrology if any of the following are present 2:

• eGFR <30 mL/min/1.73 m² (approaching need for renal replacement therapy)
• Albuminuria ≥300 mg per 24 hours (nephrotic-range proteinuria)
• Rapid decline in eGFR (>5 mL/min/1.73 m² per year or >10 mL/min/1.73 m² over 5 years)
• Uncertainty about etiology of kidney disease
• Difficult management issues such as resistant hypertension or electrolyte abnormalities
• Rapidly progressing kidney disease

Monitoring Frequency

• eGFR and UACR: Measure at least annually 1
• In patients at higher risk for progression (elderly, diabetic, hypertensive), assess renal function more frequently 3
• Laboratory monitoring for complications: Every 6-12 months for Stage 3 CKD 1
• More frequent monitoring (every 3-5 months) is indicated if eGFR continues to decline toward Stage 4 (<30 mL/min/1.73 m²) 1

Vaccination

• Hepatitis B vaccination is indicated early in patients likely to progress to end-stage kidney disease 1

Critical Pitfalls to Avoid

• Do not assume eGFR alone captures all kidney function: Always assess albuminuria and clinical context, as eGFR reflects only glomerular filtration under specific conditions 6
• Do not continue nephrotoxic medications: The risk of acute-on-chronic kidney injury is substantially elevated at this level of function 5
• Do not delay nephrology referral if rapid progression or high-risk features are present, as early intervention improves outcomes 2
• Do not overlook cardiovascular risk: CKD at this stage markedly increases cardiovascular disease risk, requiring aggressive risk factor modification 1, 2