Kidney Week

Abstract: FR-PO0085

Acute Interstitial Nephritis in a Tertiary Care Center: A Retrospective Study with Emphasis on Immune Checkpoint Inhibitors

Session Information

• AKI: Epidemiology and Clinical Trials
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 102 AKI: Clinical, Outcomes, and Trials

Authors

• Ogrotis, Ioannis, Panepistemiako Geniko Nosokomeio Attikon, Athens, Attica, Greece

Ioannis Ogrotis, MD

• Nikolopoulos, Petros, Panepistemiako Geniko Nosokomeio Attikon, Athens, Attica, Greece

Petros Nikolopoulos, PhD

• Tsotsorou, Ourania, Panepistemiako Geniko Nosokomeio Attikon, Athens, Attica, Greece

Ourania Tsotsorou, MD

• Pantzopoulou, Evangelia, Panepistemiako Geniko Nosokomeio Attikon, Athens, Attica, Greece

Evangelia Pantzopoulou, MD

• Drouzas, Konstantinos, Panepistemiako Geniko Nosokomeio Attikon, Athens, Attica, Greece

Konstantinos Drouzas, MD, MPH

• Liapis, Georgios, Ethniko kai Kapodistriako Panepistemio Athenon, Athens, Attica, Greece

Georgios Liapis

• Lionaki, Sophia, Panepistemiako Geniko Nosokomeio Attikon, Athens, Attica, Greece

Sophia Lionaki, MD, PhD

Background

Acute interstitial nephritis (AIN) is a recognized but underdiagnosed cause of acute kidney injury (AKI), often due to limited clinical suspicion and the infrequent use of kidney biopsy. With the increasing use of immune checkpoint inhibitors (ICIs), AIN has emerged as a notable immune-related adverse event. This study aimed to assess the frequency, etiology, and outcomes of biopsy-proven AIN in a tertiary care setting.

Methods

We retrospectively reviewed kidney biopsies performed between February 2021 and February 2025. Cases with a histopathologic diagnosis of AIN were identified. Clinical data, including demographics, etiologic factors, treatment, and outcomes, were extracted from medical records.

Results

Among 260 biopsies performed , 13 cases (5%) were diagnosed with AIN. The mean age was 62.3 ± 10.9 years; 84.6% were male. At presentation, mean serum creatinine was 3.24 ± 1.04 mg/dL and eGFR was 24.9 ± 17 ml/min/1.73 m². ICIs were implicated in 10 cases (76.9%), infections in 2 (15.4%), and warfarin in 1 (7.7%). All patients had sterile pyuria (mean: 11.7 ± 4.9 WBCs/hpf); mean 24-hour proteinuria was 706.2 ± 1590.8 mg. Three patients (23.1%) required temporary hemodialysis. All received corticosteroids; one also received mycophenolate mofetil. After a mean follow-up of 10.5 ± 8 months, 7 patients (53.8%) had full renal recovery, and 4 (30.7%) had partial recovery. No patient progressed to end-stage kidney disease. Three patients (23.1%) died due to underlying malignancy.

Conclusion

AIN accounted for 5% of biopsies in our center, with ICIs as the predominant etiology. These findings highlight the need for increased clinical awareness and routine renal monitoring in patients receiving immunotherapy.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025pzmmq8dm