Kidney diseases with chronic renal failure in the Italian renal biopsy registries

The prevalence of chronic renal failure (CRF) at the time of kidney biopsy ranges between 5% and 37% in different renal biopsy registries. This wide variability is mainly dependent on the different definitions of CRF. In the period 1998-2006, the Triveneto Renal Biopsy Registry recorded 816 cases with CRF (defined as serum creatinine persistently > or =1.5 mg/dL), accounting for a prevalence of 27%. At the time of biopsy, the average age and glomerular filtration rate were 54 years and 41 mL/min, respectively; 70% of CRF patients are men and the prevalence of CRF increases with age. IgA nephropathy (IgAN) is the main histological form of glomerulonephritis, accounting for 23% of all cases of CRF. However, in subjects older than 65 years, membranous glomerulonephritis (MG) exceeds IgAN, thus becoming the main diagnosis in elderly patients with renal impairment. With a cutoff value for proteinuria of 3 g/day, the main diagnoses in cases with proteinuria below and above the cutoff are IgAN and MG, respectively. IgAN remains the main histological form of nephropathy throughout all levels of renal failure. These data confirm the findings of the Italian Registry of Renal Biopsies, but correspond only in part with data from other registries. The differences can to a certain extent be explained by the different criteria for the definition of renal impairment, patient selection, and differences in diagnosis among registries.