A Case of Omeprazole-Associated Acute Interstitial Nephritis.

Acute interstitial nephritis (AIN) is characterized by an inflammatory infiltrate of the interstitium of the kidney, typically causing a decline in kidney function. Drug-induced AIN (also called allergic AIN) is a type of AIN. Common drugs associated with AIN are antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), and proton pump inhibitors (PPIs). A 59-year-old male with a history of recent laparoscopic robotic sleeve gastrectomy presented to the emergency department with five weeks of progressively worsening fatigue, nausea, and lightheadedness. Postoperatively, he was prescribed omeprazole 20 mg daily for gastric ulcer prophylaxis. His other home medications were amlodipine, atorvastatin, ursodiol, and budesonide-formoterol fumarate nebulizer. His physical examination was normal. Laboratory studies revealed elevated creatinine of 4.19 mg/dL from a baseline of 0.9 mg/dL two months ago and the presence of urine eosinophils. The etiology of this elevated creatinine was unclear, prompting CT-guided left renal biopsy. The biopsy showed diffuse interstitial inflammatory infiltration with numerous lymphocytes, a large number of neutrophils, and scattered eosinophils, consistent with the allergic type of AIN. Omeprazole was discontinued and the patient received a seven-day course of prednisone. Despite treatment, permanent renal damage occurred, and the patient's new baseline creatinine was 2.3 mg/dL. AIN caused by PPIs should be considered in the differential diagnosis of acute kidney injury (AKI). AIN can be difficult to diagnose, presenting with nonspecific symptoms, such as oliguria, malaise, nausea, and vomiting. An accurate and timely diagnosis can help prevent and treat worsening renal failure.