At what stage of Kidney Disease: Improving Global Outcomes (KDIGO) should a patient be referred to a nephrologist?

When to Refer Grade 4 KDIGO (Stage G4 CKD) to Nephrology

All patients with KDIGO grade 4 CKD (eGFR 15-29 mL/min/1.73 m²) should be referred to nephrology without exception, as this represents severe kidney disease requiring specialist co-management and preparation for potential renal replacement therapy. 1

Primary Referral Threshold

• eGFR <30 mL/min/1.73 m² is an absolute indication for nephrology referral according to major guidelines, which encompasses all of KDIGO grade 4 CKD 1, 2
• This threshold applies regardless of whether kidney function appears stable, as patients at this stage require multidisciplinary planning for potential progression to kidney failure 1

Critical Timing Considerations

• Refer immediately upon documentation of eGFR <30 mL/min/1.73 m² rather than waiting for further decline 1
• Late referral (defined as <1 year before renal replacement therapy initiation) is associated with significantly increased morbidity and mortality 1, 3
• At grade 4 CKD, the risk of kidney failure requiring renal replacement therapy within 1 year exceeds 10-20%, meeting the threshold for urgent specialist evaluation 3

Additional High-Priority Referral Triggers in Grade 4 CKD

Even if eGFR is borderline at 30 mL/min/1.73 m², refer immediately if any of these features are present:

• Rapid progression: eGFR decline >5 mL/min/1.73 m² per year 1
• Abrupt sustained eGFR decrease >20% after excluding reversible causes 1
• Significant proteinuria: >1 g/day (ACR ≥60 mg/mmol or PCR ≥100 mg/mmol) 1
• Uremic symptoms: nausea, vomiting, altered mental status, or other signs of uremia 3
• Refractory hypertension: requiring 4 or more antihypertensive agents 1
• Persistent electrolyte abnormalities: particularly hyperkalemia or metabolic acidosis 1, 3

Special Populations Requiring Expedited Referral

• Diabetic patients with eGFR <30 mL/min/1.73 m² require nephrology co-management for optimization of kidney-protective therapies and management of diabetic complications 1
• Patients with uncertain etiology of kidney disease (absence of diabetic retinopathy despite diabetes, heavy proteinuria, active urine sediment, or hematuria) need specialist evaluation for potential kidney biopsy 1
• Hereditary kidney disease patients require genetic counseling and family screening 1

What Nephrology Referral Accomplishes at Grade 4

The specialist consultation enables:

• Renal replacement therapy planning: education about hemodialysis, peritoneal dialysis, and transplant options before urgent need arises 1, 3
• Vascular access planning: timely creation of arteriovenous fistula (requires 3-6 months to mature) if hemodialysis is anticipated 3
• Transplant evaluation: assessment for preemptive kidney transplantation eligibility 3
• Management of CKD complications: anemia, mineral bone disease, metabolic acidosis, and hyperkalemia 2
• Medication optimization: adjustment of nephrotoxic medications and appropriate dose reductions 1, 2
• Dietary counseling: protein and electrolyte restriction through renal dietitian 3

Common Pitfalls to Avoid

• Do not delay referral to "optimize" medical management first—grade 4 CKD requires concurrent specialist involvement 3
• Do not assume stability means referral can be deferred; even stable grade 4 CKD requires nephrology co-management for complication prevention 1
• Do not wait for uremic symptoms to develop before referring, as this represents late referral with worse outcomes 3
• Do not discontinue ACE inhibitors/ARBs for minor creatinine increases (<30%) without nephrology input, as these provide kidney protection 1
• Avoid nephrotoxic medications including NSAIDs, and ensure all medications are renally dosed 3, 2

The Only Exception

The sole circumstance where grade 4 CKD might not require nephrology referral is in patients with very advanced age or severe comorbidities indicating short life expectancy where the focus is purely comfort care and renal replacement therapy would not be pursued 1. Even in these cases, a single nephrology consultation may help clarify prognosis and guide conservative management.