I have an estimated glomerular filtration rate (eGFR) of 18 mL/min/1.73 m²; what does this indicate and what immediate management should be undertaken?

Stage 5 Chronic Kidney Disease: Immediate Management Required

An eGFR of 18 mL/min/1.73 m² indicates Stage 4 chronic kidney disease (CKD), representing severely reduced kidney function that requires urgent nephrology referral and preparation for renal replacement therapy. 1

Disease Classification and Prognosis

• This eGFR level falls within Stage G4 CKD (15-29 mL/min/1.73 m²), representing approximately 15% of normal kidney function and indicating severe kidney impairment 1, 2
• At this stage, patients face substantially elevated risks of cardiovascular disease, CKD progression to end-stage kidney disease, and mortality 1, 3
• The kidneys are approaching the point where they can no longer adequately filter waste products, maintain electrolyte balance, or regulate fluid status 2

Immediate Mandatory Actions

Nephrology Referral (Urgent)

Immediate referral to nephrology is mandatory at eGFR <30 mL/min/1.73 m² 1, 3

• This patient meets absolute criteria for specialist involvement given eGFR of 18 mL/min/1.73 m² 1
• Referral should occur even if the patient has no symptoms, as preparation for renal replacement therapy requires months of planning 3

Comprehensive CKD Complication Screening

Initiate screening for all Stage 4 CKD complications immediately 1, 3:

• Electrolyte monitoring: Check serum potassium, sodium, bicarbonate, calcium, and phosphorus
• Metabolic acidosis assessment: Measure serum bicarbonate (metabolic acidosis is common at this stage) 2
• Anemia evaluation: Check hemoglobin and iron studies (anemia from decreased erythropoietin production is nearly universal) 2
• Mineral bone disease: Measure serum calcium, phosphorus, and parathyroid hormone (PTH) 3
• Volume status and blood pressure: Assess for fluid overload and ensure BP target <130/80 mmHg 3, 2

Medication Review and Adjustment

All medications must be reviewed immediately for dose adjustment or discontinuation 3:

• Many medications require significant dose reductions when eGFR <30 mL/min/1.73 m² 2
• NSAIDs must be strictly avoided as they reduce renal blood flow and can precipitate acute kidney injury 3
• Metformin should be discontinued at eGFR <30 mL/min/1.73 m² due to lactic acidosis risk 1

Diabetes-Specific Management (If Applicable)

Glycemic Control Adjustments

• Continue SGLT2 inhibitors (canagliflozin or dapagliflozin) if already prescribed, as they provide cardiovascular and kidney benefits even at eGFR ≥20 mL/min/1.73 m² 1
• Do not initiate new SGLT2 inhibitors at eGFR <20 mL/min/1.73 m² (this patient at 18 mL/min/1.73 m² is below threshold) 1
• Preferred agents at this eGFR: GLP-1 receptor agonists (dulaglutide, semaglutide, or liraglutide) which are safe and effective 1
• Target HbA1c of 7% to delay further CKD progression 1, 3

Proteinuria Assessment

• Measure urine albumin-to-creatinine ratio (UACR) if not recently done 1, 3
• If UACR ≥300 mg/g, consider nonsteroidal mineralocorticoid receptor antagonist (if eGFR ≥25 mL/min/1.73 m²) to reduce cardiovascular events and CKD progression 1

Dietary Modifications

Implement strict dietary restrictions immediately 1, 2:

• Protein restriction: Limit to 0.8 g/kg body weight per day to reduce uremic toxin accumulation 1
• Sodium restriction: <2 g/day to control blood pressure and reduce fluid retention 3, 2
• Potassium restriction: Typically necessary to prevent life-threatening hyperkalemia 2
• Phosphorus restriction: Required to prevent mineral bone disease progression 2

Renal Replacement Therapy Planning

Timing Considerations

• Dialysis is typically indicated when eGFR falls below 15 mL/min/1.73 m² or when uremic symptoms develop 2, 4
• At eGFR 18 mL/min/1.73 m², the patient is approaching this threshold and planning must begin immediately 2
• Evidence shows no survival advantage to starting dialysis at eGFR >5 mL/min/1.73 m² in asymptomatic patients, but preparation should start well before this point 4

Preparation Steps

• Discuss dialysis modality options (hemodialysis vs peritoneal dialysis) with nephrology 1
• If hemodialysis is chosen, plan for vascular access creation (arteriovenous fistula requires 3-6 months to mature) 1
• Evaluate for kidney transplant candidacy if appropriate 2
• Administer hepatitis B vaccination early, as patients likely to progress to end-stage kidney disease require this 3

Monitoring Frequency

Increase monitoring intensity immediately 3, 2:

• eGFR and UACR: Every 3 months (more frequent than annual monitoring at higher eGFR levels)
• Electrolytes, bicarbonate, calcium, phosphorus: Every 1-3 months
• Hemoglobin and iron studies: Every 3 months
• PTH: Every 3-6 months

Critical Pitfalls to Avoid

Diagnostic Accuracy

• eGFR calculations have limitations in extremes of muscle mass, malnutrition, and non-steady state conditions 2
• Consider measuring cystatin C-based eGFR if creatinine-based estimate seems discordant with clinical picture, as creatinine estimates are inaccurate in 16-20% of individuals with eGFR <60 mL/min/1.73 m² 1
• Repeat eGFR within 3 months to confirm chronicity, as CKD requires persistent abnormalities for ≥3 months 3

Underestimating Urgency

• Do not delay nephrology referral - this is Stage 4 CKD requiring immediate specialist involvement 1, 3
• Do not overlook cardiovascular risk, which is markedly elevated at this stage and requires aggressive risk factor modification 3, 2
• Rapid decline in eGFR (>5 mL/min/1.73 m²/year) is associated with worse outcomes than stable severe CKD 2

Medication Errors

• Failure to adjust medication doses is a common and dangerous error at this eGFR level 3, 2
• Continuing metformin at eGFR <30 mL/min/1.73 m² risks fatal lactic acidosis 1
• NSAID use can precipitate acute-on-chronic kidney injury requiring emergency dialysis 3