Do Histopathological Findings of Kidney Biopsies Performed in Patients with Acute Kidney Injury Differ with Age?

Objective: Acute kidney injury (AKI) occurs in various conditions with different clinical presentations. Kidney biopsy (KB) is recommended when pre-renal and post-renal causes have been excluded, and the cause of AKI is unclear. We aimed to determine the histopathological features in patients with AKI and compare the frequency of the underlying causes in patients with different age groups. Methods: This retrospective study was performed on all patients who underwent KB for AKI at our institution between January 2006 and April 2021. Demographic, clinical, and laboratory data and histopathological results were retrieved from the patients' files. Patients aged 60 years and older were regarded as elderly. The distribution of renal diseases was compared between the age groups. Results: Overall, 767 kidney biopsies were performed at our institution for 15 years. Of these, 171 (22.2%) had unexplained AKI, of whom 35% were elderly. Males were predominated in both groups. The most common diagnosis was glomerular diseases (71.9%), followed by tubulointerstitial diseases (21.7%) and vascular lesions (5.3%). Immunoglobulin A nephropathy was the most frequent diagnosis in adults, whereas pauci-immune glomerulonephritis was the most frequent cause of AKI in the elderly. Conclusion: Our data documents the different patterns of biopsy-confirmed causes of AKI according to the age groups and points the value of biopsy since most of the pathologic diagnoses are entities that are both difficult to diagnose without biopsy and are treatable.