Clinicopathologic correlations of renal pathology in the adult population of Poland.

Background: This is the first report on the epidemiology of biopsy-proven kidney diseases in Poland.

Methods: The Polish Registry of Renal Biopsies has collected information on all (n = 9394) native renal biopsies performed in Poland from 2009 to 2014. Patients' clinical data collected at the time of biopsy, and histopathological diagnoses were used for epidemiological and clinicopathologic analysis.

Results: There was a gradual increase in the number of native renal biopsies performed per million people (PMP) per year in Poland in 2009-14, starting from 36 PMP in 2009 to 44 PMP in 2014. A considerable variability between provinces in the mean number of biopsies performed in the period covered was found, ranging from 5 to 77 PMP/year. The most common renal biopsy diagnoses in adults were immunoglobulin A nephropathy (IgAN) (20%), focal segmental glomerulosclerosis (FSGS) (15%) and membranous glomerulonephritis (MGN) (11%), whereas in children, minimal change disease (22%), IgAN (20%) and FSGS (10%) were dominant. Due to insufficient data on the paediatric population, the clinicopathologic analysis was limited to patients ≥18 years of age. At the time of renal biopsy, the majority of adult patients presented nephrotic-range proteinuria (45.2%), followed by urinary abnormalities (38.3%), nephritic syndrome (13.8%) and isolated haematuria (1.7%). Among nephrotic patients, primary glomerulopathies dominated (67.6% in those 18-64 years of age and 62.4% in elderly patients) with leading diagnoses being MGN (17.1%), FSGS (16.2%) and IgAN (13.0%) in the younger cohort and MGN (23.5%), amyloidosis (18.8%) and FSGS (16.8%) in the elderly cohort. Among nephritic patients 18-64 years of age, the majority (55.9%) suffered from primary glomerulopathies, with a predominance of IgAN (31.3%), FSGS (12.7%) and crescentic GN (CGN) (11.1%). Among elderly nephritic patients, primary and secondary glomerulopathies were equally common (41.9% each) and pauci-immune GN (24.7%), CGN (20.4%) and IgAN (14.0%) were predominant. In both adult cohorts, urinary abnormalities were mostly related to primary glomerulopathies (66.8% in younger and 50% in elderly patients) and the leading diagnoses were IgAN (31.4%), FSGS (15.9%), lupus nephritis (10.7%) and FSGS (19.2%), MGN (15.1%) and pauci-immune GN (12.3%), respectively. There were significant differences in clinical characteristics and renal biopsy findings between male and female adult patients.

Conclusions: The registry data focused new light on the epidemiology of kidney diseases in Poland. These data should be used in future follow-up and prospective studies.