#1495 5 and 10 year kidney outcomes in acute interstitial nephritis: a retrospective single-centre cohort study

Abstract

Abstract Background and Aims Acute interstitial nephritis (AIN) is a common cause of acute kidney injury (AKI), histologically characterized by an interstitial inflammatory cell infiltrate. Data regarding long term kidney outcomes is lacking. We performed a retrospective cohort study to evaluate the long-term kidney and mortality outcomes in patients with biopsy-proven AIN between 2011-2018. Method We serve as a tertiary referral centre and sole nephrology provider for a population of over 650,000 people. We identified biopsy-proven AIN cases from the years 2011-2018 from our pathology database. Demographic data, creatinine, eGFR (calculated using CKD-EPI 2021 formula), dialysis and mortality data were collected from our electronic medical record. Ethical approval was obtained. Results Between 2011 – 2018, 576 native kidney biopsies were performed in our centre. 66 (11.5%) cases had pathologically confirmed AIN as the primary kidney diagnosis. Long-term outcome data was available for 90.9% (60). The median age at time of biopsy was 52.5 years (IQR 41.5 - 68.3). 68% of patients were male. The aetiology of AIN was medication in 42%, autoimmune in 15% and infection-associated in 3%. Of the cases of drug-induced AIN the predominant culprits agents were non-steroidal anti-inflammatories 28%, proton pump inhibitors in 24%, antibiotics 20%, with other medications in 8%. The median eGFR at the time of biopsy was 13.6 (IQR 7.9 -25.4) mls/min/1.73 m2. The median eGFR at year 1 was 47.8 (IQR 30.7 - 72.7) mls/min/1.73 m2, 54.4 (IQR 31.2 -79.6) mls/min/1.73 m2 at year 5 and 69.4 (IQR 19.9 - 86.1) mls/min/1.73 m2 at year 10. See Table 1 for results. At one year 64.3% of cases had eGFR < 60 mls/min/1.73 m2 (CKD III or higher). Interestingly the rate of CKD was lower at years 5 and 10 (54.7% and 50% respectively). GFR <30 mls/min (CKD IV or higher) were present in 25% at year 1, 26% at year 5 and 37% at year 10. 23% (14/60) people had dialysis-requiring AKI at the time of biopsy. Of these 21.4% (3) remained dialysis dependent at one year. In this group, no additional cases of ESKD were seen between years 1 through 5, one additional case of ESKD occurred by year 10. A composite outcome of kidney failure (GFR <15, dialysis or kidney transplantation) occurred in 48.2% at year 1, 54.7% at year 5 and 56.2% at year 10. Mortality data was available on 58 patients. 18.9% (11) people had died at 10 years follow-up. 8 out of the 11 deaths were within 5 years, 2 of which were within 1 year of diagnosis. Conclusion In this single centre study, kidney failure occurred in 48% of people at 10 years of follow up. 78% of dialysis-requiring cases recover independent renal function.