What is the estimated glomerular filtration rate (eGFR) for a 78‑year‑old Hispanic male with a serum creatinine of 1.68 mg/dL and a blood urea nitrogen of 41 mg/dL?

Estimated GFR for a 78-Year-Old Hispanic Male

For this 78-year-old Hispanic male with serum creatinine 1.68 mg/dL, the estimated GFR is approximately 40 mL/min/1.73 m² using the CKD-EPI equation, placing him in Stage 3B chronic kidney disease with moderately to severely decreased kidney function.

Calculation Method and Result

• The 2021 CKD-EPI equation without race is the current standard for adult GFR estimation, offering superior accuracy over older formulas and eliminating race-based adjustments. 1

• Using the MDRD equation as an alternative (when CKD-EPI is unavailable), the formula is: eGFR = 175 × (serum creatinine)^-1.154 × (age)^-0.203 × (0.742 if female) × (1.212 if Black). 1

• For this patient:

  • Age: 78 years
  • Serum creatinine: 1.68 mg/dL
  • Sex: Male (no adjustment)
  • Hispanic ethnicity (no race adjustment in modern equations)

• The calculated eGFR is approximately 40 mL/min/1.73 m², which represents Stage 3B CKD (GFR 30-44 mL/min/1.73 m²). 1, 2

Clinical Significance

• An eGFR < 60 mL/min/1.73 m² represents loss of half or more of normal adult kidney function and is associated with increased risk for cardiovascular events and CKD complications. 1, 2

• At this level of renal function, all renally cleared medications require dose adjustment to prevent toxicity and adverse drug reactions. 1, 3

• The BUN of 41 mg/dL (elevated, normal ~7-20 mg/dL) combined with the elevated creatinine confirms significant renal impairment and suggests possible uremia or volume depletion. 3

Critical Clinical Actions Required

• Calculate creatinine clearance using the Cockcroft-Gault formula for medication dosing decisions, as this provides absolute clearance (mL/min) rather than normalized values and aligns with most drug package inserts. 1

• Review all current medications immediately for renal appropriateness and adjust doses or discontinue nephrotoxic agents (NSAIDs, certain antibiotics, contrast agents). 1, 3

• Assess for uremic symptoms including nausea, fatigue, pruritus, altered mental status, and volume overload, as these may indicate need for urgent nephrology referral. 3

• Measure urine albumin-to-creatinine ratio to complete CKD staging and assess cardiovascular risk, as albuminuria significantly impacts prognosis. 1, 2

Important Caveats

• Serum creatinine alone should never be used to assess kidney function in elderly patients, as age-related muscle mass loss causes creatinine to significantly underestimate renal impairment. 1, 2

• A "normal-appearing" creatinine of 1.68 mg/dL in a 78-year-old actually represents severe renal dysfunction that would be missed without GFR calculation. 1

• For narrow-therapeutic-index drugs (vancomycin, aminoglycosides, digoxin, lithium, chemotherapy), consider cystatin C-based equations or direct GFR measurement for higher precision. 1, 3

• If eGFR continues to decline toward < 30 mL/min/1.73 m², urgent nephrology referral is required to plan for potential renal replacement therapy. 3