Percutaneous kidney biopsies in children: a 24-year review in a tertiary center in northern Portugal

Introduction: Percutaneous kidney biopsy (KB) is crucial to the diagnosis and management of several renal pathologies. National data on native KB in pediatric patients are scarce. We aimed to review the demographic and clinical characteristics and histopathological patterns in children who underwent native percutaneous KB over 24 years. Methods: Retrospective observational study of patients undergoing native percutaneous KB in a pediatric nephrology unit between 1998 and 2021, comparing 3 periods: period 1 (1998- 2005), period 2 (2006-2013), and period 3 (2014-2021). Results: We found that 228 KB were performed, 78 (34.2%) in period 1, 91 (39.9%) in period 2, and 59 (25.9%) in period 3. The median age at KB was 11 (7-14) years. The main indications for KB were nephrotic syndrome (NS) (42.9%), hematuria and/ or non-nephrotic proteinuria (35.5%), and acute kidney injury (13.2%). Primary glomerulopathies were more frequent (67.1%), particularly minimal change disease (MCD) (25.4%), IgA nephropathy (12.7%), and mesangioproliferative glomerulonephritis (GN) (8.8%). Of the secondary glomerulopathies, lupus nephritis (LN) was the most prevalent (11.8%). In group 1, hematuria and/ or non-nephrotic proteinuria were the main reasons for KB, as opposed to NS in groups 2 and 3 (p < 0.01). LN showed an increasing trend (period 1-3: 2.6%- 5.3%) and focal segmental glomerular sclerosis (FSGS) showed a slight decreasing trend (period 1-3: 3.1%- 1.8%), without statistical significance. Conclusions: The main indication for KB was NS, which increased over time, justifying the finding of MCD as main histological diagnosis. LN showed an increase in incidence over time, while FSGS cases did not increase.