What should I do since my kidney function tests are abnormal for the first time?

What to Do When Kidney Function Tests Are Abnormal for the First Time

You must repeat the abnormal kidney function tests within 3 months to confirm chronic kidney disease, as a single abnormal result is insufficient for diagnosis. 1

Immediate Next Steps

Confirm the Abnormality

• Repeat serum creatinine with calculated eGFR within 1-3 months to determine if the abnormality persists, as CKD requires abnormalities present for >3 months. 1, 2
• Obtain urinalysis with microscopy to detect cells, casts, and crystals—this is critical for differentiating causes of kidney dysfunction. 1
• Measure urine albumin-to-creatinine ratio (ACR) from a spot urine sample to quantify proteinuria, ideally using a first morning void to minimize variability. 1, 3
• Avoid testing during urinary tract infection, as this can cause false positive results for proteinuria. 3

Essential Baseline Workup

While awaiting repeat testing, complete the following to identify reversible causes and assess severity:

• Complete blood count to evaluate for anemia and infection. 1
• Serum electrolytes including sodium, potassium, calcium, magnesium, chloride, and phosphorus to identify life-threatening imbalances. 1
• Blood urea nitrogen (BUN) with calculation of BUN-to-creatinine ratio (>20:1 suggests prerenal cause, <10:1 suggests intrinsic renal disease). 1
• Renal ultrasound as the initial imaging study to assess kidney size, echogenicity, and rule out obstruction. 1

Risk Stratification Based on Repeat Testing

If Abnormality Persists (Confirming CKD)

The severity determines your monitoring frequency and need for specialist referral:

• eGFR ≥60 mL/min/1.73 m² with normal albuminuria (ACR <30 mg/g): Annual monitoring of eGFR and ACR. 3, 2
• eGFR 45-59 mL/min/1.73 m² (Stage G3a): Monitor eGFR and ACR twice yearly. 2
• eGFR 30-44 mL/min/1.73 m² (Stage G3b): Monitor eGFR and ACR three times yearly. 2
• eGFR <30 mL/min/1.73 m²: Monitor four times yearly and refer to nephrology immediately. 2, 3

Additional Referral Triggers

Refer to nephrology regardless of eGFR if:

• ACR >300 mg/g (severely increased albuminuria) on repeat testing. 3
• Unexplained hematuria with proteinuria. 2
• Rapid decline in eGFR (>5 mL/min/1.73 m² per year). 4
• Uncertain diagnosis or atypical presentation. 2

Special Considerations for Specific Populations

High-Risk Groups Requiring More Intensive Monitoring

If you have diabetes, hypertension, cardiovascular disease, or are African American, you need more frequent monitoring even with mild abnormalities:

• Annual screening is mandatory for high-risk patients even if initial values normalize. 2
• Diabetes patients should have more frequent monitoring due to higher risk of eGFR decline. 3

Drug-Related Kidney Dysfunction

If you are taking bisphosphonates (pamidronate or zoledronic acid):

• Hold the medication immediately if serum creatinine increases by ≥0.5 mg/dL or reaches an absolute value >1.4 mg/dL (if baseline was normal). 2
• Reassess kidney function every 3-4 weeks until it returns to baseline before cautiously restarting. 2
• This renal dysfunction is often reversible if detected early. 2

Critical Actions to Avoid Further Kidney Damage

• Avoid iodinated contrast unless absolutely necessary for diagnosis, as it can worsen kidney function. 1
• Review all medications for nephrotoxins, particularly NSAIDs, and adjust dosing for antibiotics and other renally cleared drugs. 4
• Ensure adequate hydration but avoid indiscriminate fluid administration without assessing volume status. 5

What the Repeat Testing Will Tell You

If Values Normalize on Repeat

• This suggests acute kidney injury (AKI) rather than CKD, which has resolved. 1
• Identify and address the precipitating cause (dehydration, medications, infection). 1
• Continue annual monitoring as you remain at higher risk for future kidney problems. 3

If Values Remain Abnormal

• This confirms chronic kidney disease requiring ongoing management and monitoring as outlined above. 2, 4
• The pattern of abnormality (reduced eGFR vs. albuminuria vs. both) guides treatment strategy. 2

Common Pitfalls to Avoid

• Relying on a single measurement can lead to misdiagnosis, as eGFR and ACR values fluctuate due to various factors including hydration status, recent protein intake, and exercise. 3
• Assuming normal kidney size excludes CKD, as diabetic nephropathy and infiltrative disorders can present with normal-sized kidneys. 1
• Delaying nephrology referral when eGFR is <30 mL/min/1.73 m², as early specialist involvement improves outcomes. 2, 4