American Board of Internal Medicine (ABIM) Certification Practice Exam

At what estimated glomerular filtration rate (eGFR) should patients with stage G4 or G5 chronic kidney disease be referred to a nephrologist for management?

1. 30 mL/min/1.73 m2

2. 25 mL/min/1.73 m2

3. 20 mL/min/1.73 m2

4. 15 mL/min/1.73 m2

The correct answer is: 20 mL/min/1.73 m2

Patients with stage G4 or G5 chronic kidney disease typically require specialized management due to the complexities and potential complications associated with advanced kidney dysfunction. When considering referral to a nephrologist, an eGFR threshold that indicates significant renal impairment is crucial. An eGFR of 20 mL/min/1.73 m² represents a critical point in kidney function, as it indicates severe renal impairment that often leads to complications such as volume overload, electrolyte abnormalities, and the potential need for renal replacement therapy. At this level of kidney function, a nephrologist can provide valuable interventions, including preparing for dialysis or kidney transplantation, managing other associated conditions, and adjusting treatment protocols that are appropriate for patients with very limited renal function. The other eGFR values, while indicative of decreased kidney function, do not specifically capture the advanced stages of chronic kidney disease where nephrology input is particularly beneficial. Therefore, an eGFR of 20 mL/min/1.73 m² is the most suitable threshold for referring these patients to a nephrologist for further evaluation and management.