When should a patient be referred to a nephrologist (kidney specialist)?

When to Refer to Nephrology

Refer all patients with eGFR <30 mL/min/1.73 m² to a nephrologist immediately, as this threshold represents stage 4 CKD where specialist consultation has been proven to reduce costs, improve quality of care, and delay dialysis. 1, 2

Absolute Indications for Nephrology Referral

Based on Kidney Function

• eGFR <30 mL/min/1.73 m²: This is a mandatory referral threshold regardless of other factors 1, 2
• Rapid decline in eGFR: Decline >5 mL/min/1.73 m² per year or sustained decrease >20% after excluding reversible causes 2, 3
• Stage 4 CKD (eGFR 15-29): Consultation at this stage reduces mortality and improves outcomes 1

Based on Proteinuria/Albuminuria

• Heavy proteinuria: Protein excretion >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol) 2
• Persistent albuminuria: Despite optimal treatment with ACE inhibitors or ARBs 2

Based on Urine Findings

• Active urine sediment: Urinary red cell casts or RBC >20 per high power field that is sustained and unexplained 1, 2

Conditional Indications (eGFR 30-60 mL/min/1.73 m²)

For patients with eGFR 30-44 mL/min/1.73 m², consider referral but not mandatory unless complications arise 1

For patients with eGFR 45-60 mL/min/1.73 m², refer if any of the following are present: 1

• Uncertain etiology: Duration of type 1 diabetes <10 years, absence of diabetic retinopathy, or abnormal renal ultrasound findings
• Resistant hypertension: Requiring 4 or more antihypertensive agents 2
• Rapid fall in GFR: As defined above
• Active urinary sediment: As defined above

Management Complications Requiring Referral

Refer for difficult-to-manage complications at any eGFR level: 1

• Anemia of CKD
• Secondary hyperparathyroidism or metabolic bone disease
• Persistent electrolyte disturbances (especially hyperkalemia)
• Metabolic acidosis

Special Populations

Diabetic Patients

• eGFR <30: Mandatory referral 1, 2
• Uncertain kidney disease etiology: Absence of retinopathy with kidney disease, heavy proteinuria, or active sediment suggests non-diabetic kidney disease requiring specialist evaluation 1, 2

Other High-Risk Scenarios

• Hereditary kidney disease: Any stage 2
• Recurrent or extensive nephrolithiasis 2
• Risk of kidney failure >10-20% within 1 year: Use risk calculators for assessment 2

Acute Kidney Injury

Refer patients with AKI when features suggest diagnoses other than prerenal azotemia or acute tubular necrosis 2

Timing Considerations

Early referral (when eGFR is still 30-44) improves outcomes compared to late referral (<1 year before dialysis). 2, 4 Research demonstrates that 48% of stage 2 CKD patients, 29% of stage 3 patients, and only 15% of stage 4 patients show improvement in eGFR after nephrology referral, emphasizing the benefit of earlier consultation 4

Exceptions to Referral

Patients with eGFR <30 may not require referral if: 2

• GFR is stable over time
• Diagnosis is clear and uncomplicated
• Very advanced age or severe comorbidities indicate short life expectancy

Common Pitfalls to Avoid

• Late referral: Waiting until eGFR <15 or dialysis is imminent increases morbidity and mortality 2, 5
• Missing non-diabetic kidney disease: In diabetic patients, absence of retinopathy with significant proteinuria suggests alternative diagnosis 1, 2
• Underestimating progression risk: Patients with increasing albuminuria, declining GFR, worsening hypertension, or family history of CKD progress faster 1
• Inadequate monitoring: Once referred, patients with eGFR 30-44 need monitoring every 3 months, not annually 1