The Incidence and Correlation of Renal Pathologies Based on 14-Year Kidney Biopsy Material: A Retrospective Single-Centre Study in Poland

<b>Background:</b> In recent years, Poland has observed fluctuations in kidney biopsy frequency and shifts in diagnostic patterns. These trends likely reflect evolving clinical practice, diagnostic advancements, and changing disease epidemiology. This study aimed to analyse these changes, assess biopsy-based diagnoses across age groups, and examine sex-related variability. <b>Methods:</b> We conducted a single-centre, retrospective study at a university hospital in southwestern Poland, covering 2010-2024. Data from 1969 kidney biopsies were collected, within 1291 native kidney cases analysed after excluding transplant recipients. Diagnoses were correlated with patients' age, sex, presence of diabetes, and temporal trends, and compared with previous studies. <b>Results:</b> Biopsy numbers increased over time, peaking in 2021 (154 procedures). Most were performed in patients aged 40-64 years (46.1%), followed by 18-39 years (39.1%) and ≥65 years (14.8%), with a rising proportion of elderly patients. Repeated biopsies occurred in 7.7% (second) and 0.6% (third biopsy). The most frequent diagnoses were IgAN (16.9%), FSGS (14.7%), and lupus nephritis (11.4%). In patients ≥65 years, amyloidosis (13.6%), FSGS (13.1%), vasculitis (13.1%), and membranous nephropathy (12%) predominated. The most marked sex-related difference involved lupus nephritis, accounting for 20.3% of diagnoses in women, who made up 82.3% of lupus nephritis cases. While most diseases showed male predominance, this was not evident for several, including IgAN and diabetic nephropathy. <b>Conclusions:</b> Given CKD's underdiagnosis and frequent late detection in Poland, updated multicentre studies are needed to better recognise disease patterns and raise public awareness.