Changing Tides of Acute Interstitial Nephritis: A Retrospective Observational Study from South India

[Image: see text] INTRODUCTION: The incidence of acute interstitial nephritis (AIN) has been increasing in recent years. The causes and outcomes of AIN have been changing with time and vary widely based on geographical region. METHODS: A retrospective observational study was conducted in a tertiary care center. All (n = 6234) native kidney biopsies were reviewed from January 2016 to December 2021. All biopsy-proven AIN cases were included in the study. AIN associated with systemic diseases (such as SLE, Sjogren’s, sarcoidosis, plasma cell dyscrasias), proliferative glomerulonephritis, and allograft biopsies were excluded. RESULTS: Among 6234 biopsies analyzed, there were 156 biopsy-proven AIN cases. The majority were in the 6(th) decade of life (24.4%) and males (80.8%). 50% of the patients had a history of drug intake, the most common being tenofovir (12.3%) followed by alternate forms of medications (10.3%). The majority (96.2%) presented with acute kidney injury (AKI). At the end of six months, 79.5% recovered completely, 19.2% progressed to chronic kidney disease. The presence of nephrotic range proteinuria at presentation was associated with progression to chronic kidney disease. CONCLUSION: AIN is an important cause of AKI, especially in the elderly population. Drugs are the most common cause, especially HAART follwed by alternate forms of medication. The presence of nephrotic range proteinuria was associated with increased risk of progression to chronic kidney disease.