INCIDENCE OF PRIMARY GLOMERULONEPHRITIS IN A LARGE NORTH-EASTERN ITALIAN AREA: A 13-YEAR RENAL BIOPSY STUDY

Introduction and Aims: The reported biopsy-proven glomerulonephritis (GN) incidence varies according to population characteristics. Published biopsy series have shown geographical and temporal variations in the pattern of GN. Therefore, the development of national or regional registries may help clinicians to learn more about epidemiology and distribution of this important clinical feature. Methods: To better understand the epidemiology of GN in a large north-eastern Italian area (including: Veneto, Friuli Venezia Giulia and Trentino Alto Adige regions; comprising approximately 4 millions inhabitants), we retrospectively analyzed data included in the “Triveneto” Register of Renal Biopsies (TVRRB). In particular, we evaluated kidney biopsy records, available from 1998 to 2010, of 4387 adult patients (male: 2734, female: 1653, mean patient age: 50.4 ± 17.7 years). No renal graft biopsies were included. During the study time, the criteria for renal biopsy were unchanged. The overall clinical indications to perform renal biopsy were: 38% nephrotic syndrome (NS), 23% chronic renal failure (CRF), 21% urinary abnormalities (UA), 15% acute renal failure (ARF) and 3% macroscopic hematuria (MH). Kidney diseases were divided in 5 groups: primary glomerulonephrities (PGN), secondary glomerulonephrities (SGN), tubulo-interstitial nephritis (TIN), vascular diseases and miscellaneous. For our study, we focused on PGN. Results: Demographic data showed that the mean age of biopsy has significantly and progressively increased from 1998 to 2010 (from 15% to 30% patients aged > 65 years, respectively). Older patients ( > 65 years) have been primarily biopsied for NS and ARF, while younger ( < 40 years) for UA. We found a significant increase in the number of biopsy for ARF (R2=0.44, p < 0.01) over time. According to the histological features: PGN was documented in the 61% of all biopsies and the leading types were: IgA nephropathy (31%), followed by membranous GN (25%), Focal Segmental Glomerulosclerosis (16%), mesangial proliferative GN without IgA deposition (9%), minimal change disease (7%), membrano-proliferative GN (6%), extracapillary proliferative GN (4%) and other (2%). Additionally, although we did not observe any difference in the overall number of biopsy-proven PGN during the study period, we found a significant increase in the incidence of minimal change disease (R2=0.28, p = 0.04) and extracapillary proliferative GN (R2=0.25, p = 0.03) over time. Conclusions: Our data clearly show that, in our large study area, the number of PGN has been substantially unchanged during the 13 years study period. However, we have assisted to an increment of the mean age of patients undergoing renal biopsy and to a significant enhancement of the incidence of some PGN types (minimal change disease and extracapillary proliferative GN). Therefore, our report represents a valuable contribution to better understand the GNP distribution in our country