What is the next step in treatment for a 47-year-old female with uncontrolled but improving diabetes, recent onset of impaired renal function, and hypertension, currently on lisinopril (angiotensin-converting enzyme inhibitor)/hydrochlorothiazide (diuretic) 40/25 mg daily?

Management of Acute Kidney Injury in a Diabetic Patient on ACE Inhibitor/Diuretic

The next step in management should be to discontinue the lisinopril/hydrochlorothiazide combination and evaluate for volume depletion, as this is likely a case of ACE inhibitor-induced acute kidney injury exacerbated by diuretic therapy. 1

Assessment of Current Situation

This 47-year-old female presents with:

• Doubling of serum creatinine (0.57 to 1.14)
• Elevated BUN (33, normally 9)
• History of microalbuminuria and hypertension
• Currently on lisinopril/hydrochlorothiazide 40/25 mg daily
• Improving but still uncontrolled diabetes (A1c 7.4)
• Asymptomatic
• Normal calcium levels

This clinical picture is consistent with acute kidney injury likely related to ACE inhibitor therapy combined with diuretic use.

Immediate Management Steps

1. Discontinue lisinopril/hydrochlorothiazide

   • The doubling of creatinine (>30% increase) in the setting of ACE inhibitor and diuretic therapy warrants immediate discontinuation 1
   • The elevated BUN-to-creatinine ratio suggests a pre-renal component, likely volume depletion from the hydrochlorothiazide

2. Assess and correct volume status

   • Evaluate for signs of volume depletion
   • Consider gentle volume repletion if clinically indicated
   • Avoid NSAIDs (patient already denies use)

3. Monitor renal function

   • Repeat serum creatinine, BUN, and electrolytes in 3-5 days
   • Check urinalysis to assess for proteinuria and hematuria

Further Diagnostic Workup

After discontinuation of the offending medications:

1. Evaluate for other causes of acute kidney injury

   • Urinalysis with microscopy
   • Urine protein-to-creatinine ratio
   • Renal ultrasound to rule out obstruction

2. Assess for diabetic nephropathy progression

   • Quantify albuminuria (spot urine albumin-to-creatinine ratio)
   • Calculate estimated GFR

Alternative Antihypertensive Strategy

Once renal function stabilizes:

1. Consider alternative antihypertensive regimen

   • If renal function returns to baseline, consider reintroducing ACE inhibitor at a lower dose without the diuretic 1
   • If ACE inhibitor is not tolerated, consider an ARB as an alternative 1
   • For patients with diabetes and albuminuria, RAS blockade remains first-line therapy but requires careful monitoring 1

2. Monitoring after medication adjustment

   • Check serum creatinine and potassium within 2-4 weeks after restarting any RAS blocker 1
   • Continue RAS blocker unless creatinine rises by more than 30% 1

Common Pitfalls to Avoid

1. Continuing ACE inhibitor despite significant creatinine elevation

   • A rise in creatinine >30% warrants discontinuation of the ACE inhibitor 1

2. Failure to recognize volume depletion

   • Diuretics can cause intravascular volume depletion, which is the most common avoidable reason for creatinine rise with ACE inhibitors 1

3. Ignoring other potential nephrotoxins

   • While the patient denies NSAID use, other medications or exposures should be reviewed

4. Overlooking bilateral renal artery stenosis

   • ACE inhibitor-induced acute kidney injury can unmask underlying renovascular disease 1

5. Inadequate follow-up

   • Close monitoring of renal function is essential after medication changes

By following this approach, you can effectively manage this case of acute kidney injury while developing an appropriate long-term strategy for blood pressure control and renoprotection in this patient with diabetes and microalbuminuria.