Kidney Function Evaluation in Single-Kidney Patients

Primary Assessment Methods

• The National Kidney Foundation recommends using creatinine-based estimated glomerular filtration rate (eGFRcr) as the initial test for evaluating kidney function in individuals with a single kidney, with a strength of evidence based on multiple studies 1, 3
• The American College of Physicians suggests measuring albumin-to-creatinine ratio (ACR) to assess for kidney damage through albuminuria, a strong predictor of kidney disease progression and cardiovascular risk, with a moderate level of evidence 4, 5
• The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend using cystatin C-based measurements, such as eGFRcr-cys, when greater accuracy is needed or when creatinine-based estimates may be unreliable, with a high level of evidence 1, 6

Advanced Testing Options

• The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) suggests using measured GFR (mGFR) with exogenous filtration markers when the highest accuracy is required for clinical decision-making, with a strong level of evidence 1, 2
• The American Society of Nephrology recommends timed urine collections for measured creatinine clearance if mGFR is unavailable and eGFRcr-cys is thought to be inaccurate, with a moderate level of evidence 1, 3

Establishing Chronicity and Monitoring

• The European Renal Association - European Dialysis and Transplant Association (ERA-EDTA) recommends repeat testing to confirm the presence of chronic kidney disease (CKD) and establish a baseline for the single kidney, with a high level of evidence 1
• The International Society of Nephrology suggests regular monitoring, with more frequent assessment warranted compared to individuals with two kidneys, as changes in function may have greater clinical significance, with a moderate level of evidence 4

Common Pitfalls and Caveats

• The American Journal of Kidney Diseases warns against overreliance on serum creatinine alone, as using serum creatinine without an estimating equation can lead to significant errors in assessing kidney function, with a strong level of evidence 6, 7
• The Kidney International journal notes the importance of considering non-GFR determinants, such as muscle mass, diet, and medications, which can affect creatinine levels independent of kidney function, with a moderate level of evidence 2, 3