A 66-year-old man comes to the office for a follow-up visit. The patient was hospitalized 3 months ago for an upper gastrointestinal bleed. A duodenal ulcer with oozing hemorrhage was found on endoscopy and treated with thermal coagulation. Testing for infection with Helicobacter pylori was negative. The patient had taken nonsteroidal anti-inflammatory drugs frequently before the bleed but no longer uses them. His hemoglobin at discharge was 9.2 g/dL. Since this hospitalization, the patient has not noticed any melena, hematochezia, lightheadedness, changes in urine appearance or output, or abdominal pain. However, over the last 3 days, he has developed subjective fever, nausea, and malaise. Other review of systems is negative. The patient's other medical history includes hypertension, chronic kidney disease (baseline creatinine 1.3-1.5 g/dL), osteoarthritis, and hyperlipidemia. Medications include lisinopril, amlodipine, carvedilol, omeprazole, and atorvastatin. He has no known drug allergies.
Temperature is 38.1 C (100.6 F), blood pressure is 142/82 mm Hg, pulse is 85/min, and respirations are 16/min. Examination shows moist mucous membranes, no jugular venous distension, normal breath sounds, and no peripheral edema. The patient's abdomen is soft and nontender. Laboratory results are as follows:
Which of the following is the most appropriate next step in management of this patient?

Question

A 66-year-old man comes to the office for a follow-up visit.  The patient was hospitalized 3 months ago for an upper gastrointestinal bleed.  A duodenal ulcer with oozing hemorrhage was found on endoscopy and treated with thermal coagulation.  Testing for infection with Helicobacter pylori was negative.  The patient had taken nonsteroidal anti-inflammatory drugs frequently before the bleed but no longer uses them.  His hemoglobin at discharge was 9.2 g/dL.  Since this hospitalization, the patient has not noticed any melena, hematochezia, lightheadedness, changes in urine appearance or output, or abdominal pain.  However, over the last 3 days, he has developed subjective fever, nausea, and malaise.  Other review of systems is negative.  The patient's other medical history includes hypertension, chronic kidney disease (baseline creatinine 1.3-1.5 g/dL), osteoarthritis, and hyperlipidemia.  Medications include lisinopril, amlodipine, carvedilol, omeprazole, and atorvastatin.  He has no known drug allergies.
Temperature is 38.1 C (100.6 F), blood pressure is 142/82 mm Hg, pulse is 85/min, and respirations are 16/min.  Examination shows moist mucous membranes, no jugular venous distension, normal breath sounds, and no peripheral edema.  The patient's abdomen is soft and nontender.  Laboratory results are as follows:
 Which of the following is the most appropriate next step in management of this patient?

Quizplus · Accepted Answer

11ec193a_990e_20a8_853d_79dce88ca859_MD0002_00 This patient has developed a rapid decline from his baseline chronic renal dysfunction 3 months earlier, likely following initiation of a proton pump inhibitor (PPI) in the setting of gastrointestinal bleed. He has fevers and eosinophilia, and urinalysis shows sterile pyuria, hematuria, mild proteinuria, and white blood cell casts. This should raise concern for acute interstitial nephritis (AIN). AIN is characterized by inflammatory infiltration of the renal interstitium with resultant kidney injury; 75% of cases are drug-related. Common offenders include PPIs, antibiotics, and nonsteroidal anti-inflammatory drugs. Onset generally occurs weeks to months after first exposure; however, symptoms occur more rapidly (days) after second exposure. Classically, drug-induced AIN causes fever, rash, and eosinophilia, although all 3 symptoms occur together in only 10% of cases. Characteristic urinalysis findings include hematuria, sterile pyuria, and white blood cell casts; proteinuria may be present in varying degrees. Urine eosinophils are relatively common (up to 40% of patients) but occur in a multitude of diseases (eg, prostatitis, atheroemboli); therefore, their presence is supportive but nondiagnostic (Choice D). Offending medications should be discontinued immediately. Renal biopsy is diagnostic but is not required in patients whose renal function improves after medication withdrawal (Choice B). Glucocorticoids are often used in patients who fail to improve after medication withdrawal, although the benefits remain unclear (Choice E). (Choice C) Urine protein electrophoresis is used for the workup for multiple myeloma, which can cause worsening renal function, anemia, and proteinuria on urinalysis but would not be expected to cause pyuria or white blood cell casts. This patient's hemoglobin is improving after his gastrointestinal bleed, his calcium level is not elevated, and he has no back pain, all of which make multiple myeloma unlikely. Educational objective: Acute interstitial nephritis is a common cause of renal dysfunction and is frequently caused by proton pump inhibitors, antibiotics, and nonsteroidal anti-inflammatory drugs. Characteristic presentation can include fever, rash, and eosinophilia; urinalysis often shows pyuria, hematuria, and white blood cell casts. Offending medications should be stopped immediately. __________

A 66-Year-Old Man Comes to the Office for a Follow-Up