In a female patient with serum potassium 4.0 mmol/L, urinalysis within normal limits, estimated glomerular filtration rate 72 mL/min/1.73 m², and no use of angiotensin‑converting enzyme inhibitors or angiotensin receptor blockers, how should I manage her likely prerenal azotemia?

Management of Prerenal Azotemia in This Patient

In this patient with normal potassium (4.0 mmol/L), normal urinalysis, eGFR 72 mL/min/1.73 m², and no ACE inhibitor or ARB use, cautiously reduce diuretic dosing if she is on diuretics, assess volume status clinically, and address any reversible causes of prerenal azotemia such as volume depletion, NSAIDs, or intercurrent illness.

Initial Assessment and Diagnosis

The clinical picture suggests prerenal azotemia in the context of Stage 3a CKD (eGFR 72 mL/min/1.73 m²). The key is determining whether this represents:

• Acute kidney injury (AKI) superimposed on CKD
• Chronic stable kidney disease
• Acute kidney disease (AKD) - the transitional state between AKI and CKD

Check for volume depletion first. Assess:

• Orthostatic vital signs
• Mucous membrane moisture
• Skin turgor
• Recent weight changes
• Fluid intake/output history

Medication Review

Immediately review and address nephrotoxic exposures 1:

• NSAIDs: Stop if present - these cause diuretic resistance and renal impairment
• Diuretics: If the patient is on loop or thiazide diuretics, assess for hypovolemia/dehydration and consider dose reduction 1
• Over-the-counter medications: Ask specifically about purchased medications that may contain NSAIDs
• Herbal/complementary medicines: Document all non-prescribed substances 2

Management Algorithm

If Volume Depleted:

1. Stop or reduce diuretics temporarily 1
2. Encourage appropriate fluid intake - avoid excessive hypotonic fluids which can cause hyponatremia 1
3. Recheck creatinine in 1-2 weeks after correcting volume status 3

If Euvolemic:

1. Exclude obstruction with renal ultrasound (preferably after correcting any hypovolemia) 2
2. Review for intercurrent illness: infections, diarrhea, vomiting, excessive sweating 1
3. Monitor closely - check renal function and electrolytes in 1-2 weeks 3

When to Consider ACE Inhibitor or ARB Initiation

Do NOT start ACE inhibitors or ARBs during acute prerenal azotemia 4. These agents can worsen kidney function in volume-depleted states by reducing glomerular filtration pressure through efferent arteriolar dilation 4.

After stabilization, if she develops:

• Proteinuria (ACR ≥30 mg/mmol or PCR ≥50 mg/mmol)
• Hypertension requiring treatment
• Evidence of progressive CKD

Then ACE inhibitor or ARB would be indicated 5, 6.

Monitoring Strategy

Recheck within 1-2 weeks 3:

• Serum creatinine and eGFR
• Electrolytes (potassium remains normal, but monitor)
• Volume status assessment

If creatinine rises >20% after correcting reversible causes, consider nephrology referral 7. While eGFR 72 doesn't mandate automatic referral, an abrupt sustained decrease warrants specialist input 7.

Common Pitfalls to Avoid

• Don't start ACE inhibitors/ARBs in prerenal azotemia - they will worsen kidney function in volume-depleted states 4
• Don't over-diurese - excessive diuresis causes prerenal azotemia, hypotension, and arrhythmias 8, 1
• Don't ignore medication reconciliation - NSAIDs are frequently the culprit and may be over-the-counter 1, 2
• Don't assume chronicity based solely on eGFR 72 - this could represent AKI or AKD requiring different management 2

Follow-Up Care

Once prerenal azotemia resolves:

• Annual monitoring of eGFR and albuminuria 6
• Blood pressure control to <130/80 mmHg if hypertensive 6
• Avoid nephrotoxins - counsel on NSAID avoidance 1
• Medication dose adjustments as needed for eGFR <60 9, 6