How to manage a patient with impaired renal function (elevated creatinine) and normal estimated glomerular filtration rate (eGFR)?

Management of a Patient with Elevated Creatinine and Normal eGFR

For a 56-year-old patient with elevated creatinine (117 μmol/L) and normal eGFR, the most appropriate management is to assess for non-GFR determinants affecting creatinine levels, including diet, supplements, and medications, while maintaining routine monitoring without immediate intervention for kidney disease. 1

Initial Assessment

Interpret the Laboratory Values

• Creatinine of 117 μmol/L (approximately 1.3 mg/dL) is at the upper limit of normal range for men (62-115 μmol/L) and elevated for women (53-97 μmol/L) 1
• Normal eGFR with elevated creatinine represents a discrepancy that requires investigation

Evaluate for Non-GFR Determinants of Creatinine

• Diet factors:
  • High-protein diet or creatine supplements can increase serum creatinine without affecting actual kidney function 1, 2
  • Vegetarian diets may lower creatinine levels
• Muscle mass considerations:
  • Higher muscle mass can lead to higher creatinine production
  • Age-related muscle loss may affect creatinine levels
• Medications:
  • Review medications that may affect creatinine levels without affecting GFR
  • Some antibiotics (trimethoprim, cimetidine) can interfere with tubular secretion of creatinine

Diagnostic Approach

Confirmatory Testing

1. Repeat testing:

   • Confirm the discrepancy between creatinine and eGFR
   • Single abnormal values should not be assumed to indicate kidney disease 1

2. Enhanced GFR assessment:

   • Consider cystatin C measurement and calculate eGFRcr-cys for more accurate assessment 1
   • KDIGO guidelines recommend using eGFRcr-cys when eGFRcr may be inaccurate 3

3. Assess for kidney damage markers:

   • Measure urine albumin-to-creatinine ratio (UACR) to detect early kidney damage 3
   • Normal UACR (<30 mg/g) with normal eGFR suggests absence of kidney disease

Management Plan

If No Evidence of Kidney Disease

• Routine monitoring:
  • Annual assessment of kidney function (creatinine, eGFR, UACR) 3
  • No specific kidney-directed interventions needed

If Mild Kidney Dysfunction Suspected

• Modify risk factors:
  • Optimize blood pressure control (target <130/80 mmHg) 3
  • Manage diabetes if present (target HbA1c individualized based on patient factors) 3
  • Address cardiovascular risk factors (lipids, smoking, weight) 3

If Creatinine Elevation Due to Non-Renal Factors

• Address modifiable factors:
  • Discontinue creatine supplements if used 2
  • Adjust diet if contributing to elevated creatinine
  • Review and modify medications that may affect creatinine levels

Special Considerations

Medication Management

• No dose adjustments needed:
  • Normal eGFR generally does not require medication dose adjustments
  • For ACE inhibitors/ARBs: No dose adjustment required with normal eGFR 4

Monitoring Recommendations

• Follow-up testing:
  • Repeat creatinine and eGFR in 3-6 months
  • If values remain stable, continue annual monitoring
  • If creatinine increases or eGFR decreases, more frequent monitoring is warranted

Common Pitfalls to Avoid

1. Overdiagnosis of CKD:

   • Avoid labeling patients with CKD based solely on a single elevated creatinine value with normal eGFR 5
   • Remember that serum creatinine alone is an inadequate measure of GFR 6

2. Unnecessary nephrology referral:

   • Referral to nephrology is not indicated for isolated creatinine elevation with normal eGFR unless other concerning features are present 3

3. Overlooking non-renal causes:

   • Failing to consider supplements, diet, and muscle mass as causes of isolated creatinine elevation 2

4. Medication errors:

   • Unnecessarily adjusting medication doses based on creatinine alone when eGFR is normal

By following this approach, you can appropriately manage a patient with elevated creatinine but normal eGFR, avoiding unnecessary interventions while ensuring proper monitoring for any true kidney dysfunction.