What steps should I take if my kidney function is deteriorating, indicated by rising serum creatinine or decreasing estimated glomerular filtration rate?

What to Do When Kidney Function is Deteriorating

Immediately identify and eliminate reversible causes of rising creatinine, particularly nephrotoxic medications (NSAIDs, contrast agents), volume depletion, and urinary obstruction, while recognizing that a creatinine increase up to 20% may occur with antihypertensive therapy initiation and should not automatically trigger medication discontinuation. 1

Initial Diagnostic Assessment

Determine if this represents acute kidney injury (AKI) versus chronic kidney disease (CKD) progression:

• AKI is defined by: creatinine increase ≥0.3 mg/dL within 48 hours, OR creatinine increase ≥1.5 times baseline within 7 days, OR urine output <0.5 mL/kg/h for 6-12 hours 1
• CKD requires: abnormalities in kidney structure or function persisting for ≥3 months, OR eGFR <60 mL/min/1.73 m² for ≥3 months 1, 2
• Check urine albumin-to-creatinine ratio (ACR) immediately from a spot urine sample to assess kidney damage severity and guide treatment intensity 3
• Obtain urinalysis with microscopy to look for proteinuria, hematuria, cellular casts, or acanthocytes indicating intrinsic kidney disease 4

Eliminate Reversible Causes

Systematically address modifiable factors:

• Discontinue nephrotoxic medications immediately: NSAIDs, aminoglycosides, contrast agents, and certain supplements 1, 4
• Withdraw diuretics and provide volume challenge: albumin 20-25% at 1 g/kg/day for 2 days to exclude volume depletion as the cause 1
• Rule out urinary obstruction: obtain renal ultrasound to ensure normal findings 1
• Assess for hypotension or shock: both are reversible causes requiring immediate correction 1

Important Caveat About Medication-Induced Creatinine Changes

A slight creatinine increase up to 20% may occur when antihypertensive therapy is instituted or potentiated, but this should not be taken as progressive renal deterioration. 1 Similarly, ACE inhibitors or ARBs may cause creatinine increases up to 30% from baseline in the absence of volume depletion, which should not prompt medication discontinuation. 4

Stage the Severity

Use KDIGO staging to determine urgency:

• Stage 1 AKI: 1.5-1.9 times baseline creatinine OR ≥0.3 mg/dL increase within 48h 1
• Stage 2 AKI: 2.0-2.9 times baseline creatinine 1
• Stage 3 AKI: ≥3.0 times baseline OR creatinine ≥4.0 mg/dL OR initiation of renal replacement therapy 1

For CKD staging:

• Stage 3: eGFR 30-59 mL/min/1.73 m² 1
• Stage 4: eGFR 15-29 mL/min/1.73 m² 1
• Stage 5: eGFR <15 mL/min/1.73 m² 1

Initiate Nephroprotective Therapy

If ACR ≥30 mg/g, start ACE inhibitor or ARB immediately, even with normal blood pressure, as these are first-line nephroprotective agents. 3 ACR ≥300 mg/g strongly indicates the need for renin-angiotensin system blockade and nephrology referral. 3

Add SGLT2 inhibitor (empagliflozin, canagliflozin, or dapagliflozin) if eGFR 30 to <90 mL/min/1.73 m², as these reduce risk of renal endpoints and cardiovascular events. 3

Monitoring Strategy

Establish appropriate surveillance intervals:

• For AKI: Monitor serum creatinine and urine output to stage severity; individualize frequency based on patient risk and clinical course 1
• For Stage 3b CKD (eGFR 30-44 mL/min/1.73 m²): Monitor renal function every 3-6 months 4
• Evaluate patients 3 months after AKI for resolution, new onset, or worsening of pre-existing CKD 1

Nephrology Referral Criteria

Refer to nephrology when:

• ACR ≥30 mg/g (especially ≥300 mg/g) 3
• Uncertainty about etiology of kidney disease 3
• Rapid decline in eGFR or progressive disease 3
• Difficulty managing complications (anemia, mineral bone disease, acidosis) 3
• eGFR <30 mL/min/1.73 m² 4
• Renal function continues to decline despite addressing reversible causes 4

Blood Pressure Management

Target systolic blood pressure to 130 mmHg and <130 mmHg if tolerated, but not <120 mmHg, using ACE inhibitor or ARB as first-line agent. 3 This is particularly important if albuminuria or left ventricular hypertrophy is present. 3

Common Pitfalls to Avoid

Do not rely on serum creatinine alone: Normal creatinine does not exclude significant kidney dysfunction, as it is affected by muscle mass, age, gender, and nutritional status independent of GFR. 3, 4 Always calculate eGFR using the CKD-EPI equation. 3

Do not use eGFR formulas in acute settings: eGFR calculations assume steady-state conditions and are invalid when creatinine is acutely elevated from non-renal causes such as creatine supplementation, intense exercise, or high meat intake. 4

Consider cystatin C measurement as an alternative marker of kidney function that is not affected by muscle mass or diet when diagnostic uncertainty exists. 4