Laboratory Tests for Patients with One Kidney
For patients with one kidney, comprehensive laboratory monitoring should include serum creatinine with eGFR calculation, urinalysis with protein quantification, and electrolyte panel to assess kidney function and prevent progression to chronic kidney disease. 1
Core Laboratory Tests for Kidney Function Assessment
Essential Tests (Baseline and Regular Monitoring)
- Serum creatinine with eGFR calculation using CKD-EPI equation 2
- Urinalysis with protein assessment 2, 1
- Complete electrolyte panel including:
- Sodium (Na+)
- Potassium (K+)
- Calcium (Ca2+)
- Magnesium (Mg2+)
- Chloride (Cl-)
- Bicarbonate levels 2
- Blood urea nitrogen (BUN) 2, 1
Additional Recommended Tests
- Complete blood count (CBC) to assess for anemia 2, 1
- Serum phosphate levels to monitor mineral metabolism 1
- Parathyroid hormone (PTH) if GFR is reduced 1
- Lipid profile for cardiovascular risk assessment 1, 3
Frequency of Monitoring Based on Kidney Function
The frequency of laboratory monitoring should be determined by the patient's current kidney function status:
| GFR (mL/min/1.73 m²) | Monitoring Frequency |
|---|---|
| ≥60 (with normal UACR) | Annually |
| 45-59 | Every 6-12 months |
| 30-44 | Every 3-6 months |
| 15-29 | Every 3 months |
| <15 | Monthly |
Special Considerations for Single Kidney Patients
- More frequent monitoring may be warranted initially after kidney loss (donation, nephrectomy) 2
- Cystatin C measurement should be considered for more accurate GFR assessment, as muscle mass variations can affect creatinine-based estimates 2, 1
- Measured GFR using exogenous filtration markers may be necessary in cases where precise GFR determination is critical for clinical decisions 2
Interpreting Results in Single Kidney Patients
- A mild reduction in GFR (60-89 mL/min/1.73 m²) is common and often expected in patients with a single kidney 2
- Any albuminuria (≥30 mg/g creatinine) should prompt closer monitoring and potential intervention 2, 1
- Rapid GFR decline (>5 mL/min/1.73 m² per year) warrants immediate nephrology referral 1
Common Pitfalls to Avoid
- Relying solely on serum creatinine without calculating eGFR can lead to underestimation of kidney dysfunction 2, 4
- Failing to repeat abnormal tests - confirmation of abnormal values over 3 months is required for CKD diagnosis 2, 1
- Not adjusting medication dosages based on reduced kidney function 1
- Overlooking non-albumin proteinuria which may indicate tubular rather than glomerular damage 2
- Missing early signs of kidney dysfunction by not performing regular urinalysis 2
By implementing comprehensive laboratory monitoring, patients with a single kidney can be appropriately assessed for kidney function, allowing early intervention to prevent progression to advanced kidney disease and its associated complications.