Is a patient with impaired renal function, as indicated by an eGFR of 56, but normal creatinine and BUN levels, considered to have kidney disease?

Is This Kidney Disease?

Yes, with an eGFR of 56 mL/min/1.73 m², this patient has Stage 3a chronic kidney disease (CKD), regardless of the normal creatinine and BUN values. 1, 2

Understanding the Diagnosis

The key principle here is that eGFR below 60 mL/min/1.73 m² alone is sufficient to diagnose CKD Stage 3 or higher—no additional markers of kidney damage are required. 1, 3 This represents loss of approximately half or more of normal adult kidney function. 1, 2

Why Normal Creatinine Doesn't Rule Out CKD

• Your creatinine of 1.12 mg/dL appears "normal" by laboratory reference ranges, but serum creatinine alone is an unreliable indicator of kidney function because it doesn't account for age, sex, muscle mass, or body size. 1
• The eGFR calculation adjusts creatinine for these factors, revealing the true functional status of the kidneys. 1
• Many patients maintain seemingly normal creatinine levels despite significantly declining kidney function—this is a well-recognized clinical pitfall. 1, 4

CKD Stage 3a Classification

• Stage 3a CKD is defined as eGFR 45-59 mL/min/1.73 m², which your value of 56 falls within. 1, 2
• At this stage, the prevalence of CKD complications increases substantially. 1, 2
• Stage 3 CKD can be diagnosed based on reduced eGFR alone without requiring additional evidence of kidney damage like proteinuria. 3

Critical Next Steps Before Confirming Diagnosis

Establish Chronicity (Essential)

CKD requires proof that the abnormality has persisted for at least 3 months. 3 A single abnormal eGFR should never be assumed to represent chronic disease, as it could result from acute kidney injury. 3

You must:

• Review any past eGFR or creatinine measurements from the last 3+ months 3
• If no prior values exist, repeat the eGFR measurement in 3 months to confirm persistence 3
• Once CKD is legitimately established with documented chronicity, the diagnosis persists even if kidney function subsequently improves 3

Measure Urine Albumin-to-Creatinine Ratio (UACR)

Albuminuria assessment is mandatory to complete risk stratification, as this determines true CKD risk category independent of eGFR. 1, 3

• An albumin-to-creatinine ratio ≥30 mg/g in a spot urine sample indicates kidney damage. 1
• The presence and severity of albuminuria dramatically affects prognosis and treatment intensity. 1, 3
• Patients with Stage 3a CKD and no albuminuria have substantially better outcomes than those with albuminuria. 1

Consider Confirmatory Testing with Cystatin C

For patients with eGFR 45-59 mL/min/1.73 m² who do not have other markers of kidney damage (like albuminuria), measuring cystatin C can confirm the CKD diagnosis. 1

• Approximately two-thirds of persons with creatinine-based eGFR <60 will have cystatin C-based eGFR <60, confirming CKD. 1
• Those with confirmed CKD by both markers have markedly elevated risks for death, cardiovascular disease, and end-stage renal disease. 1

Clinical Implications

This Patient Requires:

• Annual monitoring at minimum: serum creatinine, eGFR calculation, UACR, and blood pressure at every visit 1, 3
• Medication review for nephrotoxic agents and dose adjustments based on eGFR 1, 3
• Blood pressure control with target <130/80 mmHg 3
• Cardiovascular risk reduction, as decreased eGFR is an independent predictor of cardiovascular disease and death, even in elderly patients 1, 2

Age Considerations

The definition of CKD is the same regardless of age. 1, 2 Although GFR naturally declines with aging, decreased eGFR in elderly patients remains an independent predictor of adverse outcomes and requires the same diagnostic approach and medication adjustments. 1

Common Pitfalls to Avoid

• Don't rely on creatinine or BUN alone—they grossly overestimate kidney function in many patients 1, 4
• Don't dismiss reduced eGFR as "normal aging"—it carries real clinical consequences 1, 2
• Don't diagnose CKD from a single measurement—chronicity must be established 3
• Don't forget to check for albuminuria—it's essential for complete risk assessment 1, 3