58-year-old man with fatigue and creatinine of 2.8 mg/dL
A 58-year-old retired history teacher presents to the emergency department with two weeks of progressive fatigue and nausea. Three weeks ago, he was hospitalized for community-acquired pneumonia. During that admission, he was started on pantoprazole and was discharged on a 7-day course of levofloxacin, which he completed two weeks ago. He continues to take the pantoprazole. His chronic medications include lisinopril and atorvastatin. His temperature is 37.1°C (98.8°F), blood pressure is 138/84 mmHg, and pulse is 88/min. Physical examination is unremarkable; there is no rash or dependent edema. Laboratory studies show: Sodium: 137 mEq/L Potassium: 4.8 mEq/L Bicarbonate: 21 mEq/L BUN: 60 mg/dL Creatinine: 2.8 mg/dL (baseline 1.0 mg/dL one month ago) WBC count: 8,200/mm³ with 6% eosinophils Urinalysis shows 1+ protein, 20-30 WBCs/hpf, and no bacteria. Urine culture is pending. Which of the following is the most appropriate next step in management?
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B
Explanation
Clinical Pearl:
Drug-induced acute interstitial nephritis (AIN) is a common cause of AKI and should be suspected in patients with a new rise in creatinine and sterile pyuria, even without the classic triad of fever, rash, and eosinophilia. The first step in management is always discontinuation of the offending agent.
Explanation:
This patient's presentation of acute kidney injury with sterile pyuria and mild eosinophilia, occurring weeks after the initiation of a new medication (pantoprazole), is highly suggestive of drug-induced acute interstitial nephritis (AIN). The most critical first step in managing suspected drug-induced AIN is to identify and discontinue the offending agent; in this case, the ongoing pantoprazole is the most likely cause. Administering intravenous saline would be appropriate for pre-renal AKI, but this patient is euvolemic on examination and has urinalysis findings indicative of an intrinsic renal process. Initiating prednisone is premature, as corticosteroids are typically considered only after the offending drug is stopped and if renal function does not spontaneously improve. While a renal ultrasound can rule out obstruction, it is not the most immediate and impactful intervention given the strong evidence for AIN. A renal biopsy, while definitive, is an invasive procedure reserved for cases where the diagnosis is uncertain or when there is no recovery after withdrawal of the suspected drug.
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