Severe Asymptomatic Acute Kidney Injury due to Acute Interstitial Nephritis Following Use of Non-Steroidal Anti-Inflammatory Drug

We describe a 7-year-old boy who had a mild fever lasting only a few hours and who only received two doses of ibuprofen (5 mg/kg). He became afebrile quickly but was brought for evaluation in view of transient red urine. Evaluation revealed serum creatinine of 1.7 mg/dl with normal urine tests and complements. Even after 72 h, the serum creatinine remained elevated at 1.7 mg/dl. His urinary beta-2 microglobulin was markedly elevated at 3162 ng/ml (normal <300). He underwent a kidney biopsy that showed acute tubulointerstitial nephritis (AIN). He received prednisolone at 2 mg/kg/day, and 6 weeks later, the serum creatinine was normal at 0.6 mg/dl (estimated glomerular filtration rate: 82 ml/min). He had received ibuprofen occasionally for fever earlier. AIN associated with nonsteroidal anti-inflammatory drug can cause severe acute kidney injury with no symptoms, and the only clue in such cases is a raised urinary beta-2 microglobulin in the urine.