Clinicopathological Spectrum and Outcomes in Patients with Acute Interstitial Nephritis

Background Acute interstitial nephritis (AIN) is an important cause of AKI, with significant variation in the etiology between low- and middle-income countries (LMICs) and high-income countries (HICs). The study aimed to analyze the etio-pathological factors and long-term outcomes of AIN over the past 10 years. Materials and Methods This retrospective study included 55 patients with biopsy-proven AIN admitted from February 2014 to February 2024. Patients with solid organ/bone marrow transplants, primary glomerular lesions, or <3 months of follow-up were excluded. Clinical data, histopathology, and renal function outcomes were collected. Recovery was categorized into complete recovery (CR), partial recovery (PR), or non-recovery (NR) based on serum creatinine and eGFR. Results AIN constituted 1.6% of kidney biopsies. Drugs (44%) and envenomation (29%) were the most common causes. At presentation, 34.5% required dialysis, and systemic features were infrequent. At three months, CR was observed in 29%, PR in 18%, and NR in 53%. Envenomation and immunological causes had better outcomes compared with drug-induced AIN. Underlying chronicity significantly correlated with poor recovery. Conclusion AIN's etiological spectrum differs in LMICs, with envenomation contributing substantially. Despite corticosteroid therapy, >50% of the patients exhibited incomplete recovery, emphasizing the need for early diagnosis and timely intervention to improve outcomes.