Long-Term Outcomes and Role of Corticosteroids in Biopsy-Proven Acute Interstitial Nephritis

Background The causes of Acute Interstitial Nephritis (AIN) vary in different parts of the world, and data on long-term outcomes from corticosteroid use are limited. We conducted a study to determine causes, treatments, and outcomes of biopsy-proven AIN at our center. Materials and Methods We included all biopsy-proven cases of AIN between June 2013 and June 2023. Cases of AIN, biopsy findings, and follow-up outcomes were evaluated. Results Out of 4267 biopsies screened, 235 patients had AIN, and after excluding 65 patients, 170 (4%), mean age 53.5 ± 15.5 years, and 129 (75.9%) males were included in the analysis. The causes of AIN included drugs (73.5%), infection-induced AIN (14.1%), crystal-associated AIN (5.8%), unknown causes (4.1%), and snake bites (1.2%). Among drugs, alternative medications (n=40; 23.5%), non-steroidal anti-inflammatory drugs (NSAIDs) (n=33; 19.4%), proton pump inhibitors (n=20; 11.8%), and antibiotics (n=15; 8.8%) were the most frequent causes. Corticosteroid use was documented in 121 (71.2%) patients, with 98 (57.6%) showing kidney function recovery and 30 (17.6%) exhibiting self-kidney recovery without corticosteroid ( p= 0.01) over a median follow-up of 13 months (IQR=3, 44). Median eGFR at 3 months, dialysis dependency, and short and long-term outcomes were better in the corticosteroid treatment group than in the non-treatment group. Conclusion AIN is most frequently associated with drugs, with alternative medicines being the most common. Corticosteroid use impacts short and long-term outcomes of AIN.