Can a patient have Chronic Kidney Disease (CKD) with normal estimated Glomerular Filtration Rate (eGFR) and Creatinine Clearance (CrCl) but elevated Microalbuminuria (MAC)?

From the Guidelines

Yes, a patient can have Chronic Kidney Disease (CKD) with normal estimated Glomerular Filtration Rate (eGFR) and Creatinine Clearance (CrCl) but elevated Microalbuminuria (MAC). CKD is defined as abnormalities of kidney structure or function present for more than 3 months with implications for health. While decreased GFR (less than 60 ml/min/1.73m²) is one criterion for CKD, persistent albuminuria (albumin-to-creatinine ratio ≥ 30 mg/g) is another independent marker of kidney damage, as stated in the 2023 standards of care in diabetes 1. This is particularly common in early diabetic nephropathy, where increased urinary albumin excretion often precedes any decline in filtration function.

Key Points to Consider

• The presence of albuminuria indicates damage to the glomerular filtration barrier and is associated with increased cardiovascular risk and progression to more advanced kidney disease.
• Regular screening for albuminuria is recommended in high-risk populations such as those with diabetes or hypertension, even when eGFR is normal, as emphasized by the Kidney Disease: Improving Global Outcomes (KDIGO) controversies conference in 2021 1.
• Early detection of this marker allows for interventions like ACE inhibitors or ARBs that may slow disease progression.
• The 2022 standards of medical care in diabetes also highlight the importance of considering albuminuria in the diagnosis and management of CKD, noting that UACR is a continuous measurement and differences within the normal and abnormal ranges are associated with renal and cardiovascular outcomes 1.

Implications for Management

• Prompt referral to a nephrologist is recommended for uncertainty about the etiology of kidney disease, difficult management issues, and rapidly progressing kidney disease.
• Management should include assessment of both eGFR and albuminuria to guide treatment decisions, as these are critical for effective risk stratification of persons with CKD, according to the 2023 standards of care in diabetes 1.
• Interventions aimed at reducing albuminuria, such as ACE inhibitors or ARBs, can be beneficial in slowing disease progression, even in patients with normal eGFR.

Conclusion is not needed as per the guidelines, the above statement is the final answer.

From the Research

Definition and Diagnosis of Chronic Kidney Disease (CKD)

• CKD is characterized by damage to the renal glomeruli, vascular supply, and/or tubulointerstitium, and is typically asymptomatic but may be detected incidentally via urinalysis showing proteinuria or blood test results showing an elevated creatinine level 2.
• CKD is defined as a GFR less than 60 mL/min/1.73 m2 or persistent evidence of kidney damage on imaging, biopsy, or urinalysis that persists for longer than 3 months 2.

Estimated Glomerular Filtration Rate (eGFR) and Creatinine Clearance (CrCl)

• The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most accurate creatinine-based method for estimating GFR in routine practice 2, 3.
• Cystatin C level measurement can be considered if patients have factors that might make creatinine-based equations inaccurate 2.
• The urinary CrCl method has poor precision for assessment of GFR in critically ill patients with early AKI, and should not be used as a reference method when validating new methods for assessing kidney function in this patient population 4.

Microalbuminuria (MAC) and CKD

• Proteinuria adds value to GFR estimation, and microalbuminuria is a marker of early kidney damage 3.
• A patient can have CKD with normal eGFR and CrCl but elevated microalbuminuria, as CKD is defined by persistent evidence of kidney damage, not just decreased GFR 2, 3.
• The presence of microalbuminuria can indicate early kidney damage, even if eGFR and CrCl are within normal limits 3, 5.