Trends in biopsy-confirmed kidney disease in the adult population of Central Poland: a single-region cohort of 13-year duration (2011-2023).
INTRODUCTION Demographic, socioeconomic and environmental factors, including infections, vaccination and healthcare availability, may influence the spectrum of renal diseases. OBJECTIVES This study examines trends in biopsy-confirmed kidney disease in adult Polish population (2011-2023), with emphasis on shifts during and after the COVID-19 pandemic. PATIENTS AND METHODS We retrospectively analyzed 1,662 first native kidney biopsies performed in residents of the Lodz voivodeship (population: 2 million). Clinical and histopathological data were stratified by age, sex, and time period (pre-COVID, COVID, post-COVID) and compared with those reported by the same center in 1990-2010. RESULTS Between 2011 and 2023, biopsy frequency increased from 43.9 to 102.2 per million population, with a temporary decline during COVID and a significant rise afterwards. The proportion of older patients increased, while nephrotic-range proteinuria became a less common biopsy indication. During COVID, patients presented with poorer renal function, and had higher rates of acute kidney disease. IgA nephropathy (IgAN) was the most frequent diagnosis (17.4%), with its proportion increasing during and after COVID, followed by focal segmental glomerulosclerosis (FSGS, 16.3%), membranous nephropathy (9.4%) and diabetic kidney disease (DKD, 8.0%). Minimal change disease frequency declined, other nephropathies remained stable, and a relative rise in tubulointerstitial disorders was observed. Compared with 1990-2010, the annual number of biopsies more than tripled, with a markedly older patient population and increased frequencies of FSGS, DKD and crescentic glomerulonephritis or necrotizing vasculitis. CONCLUSIONS Over three decades, biopsy frequency in the Lodz Voivodeship has increased, particularly among older adults, with IgAN becoming the most common diagnosis.