The Pisa experience of renal biopsies, 1977-2005

Although several registries collecting data of patients with kidney diseases exist, only a few specifically collect data relating to renal biopsy. Kidney biopsy has been performed routinely in Pisa since 1977; the aim of this study was to report the relative frequency of nephropathies according to gender, age at time of biopsy, clinical presentation and renal function, based on histological diagnoses during the years 1977 through 2005. During this time, 3,810 kidney biopsies were performed, of which 89.3% were from native (n=3,446) and 10.7% from transplant kidneys. Throughout this period, 5% of renal biopsies were not diagnostic, so in this paper we report data regarding 3,269 native kidney nephropathies.

During the years 1977 through 2005, data for renal biopsies were collected on specific registers filled out by clinicians. Information collected in the database included a variety of indicators, such as clinical anamnesis, creatinine clearance, daily proteinuria, hemoglobin levels, blood pressure, height and weight, clinical presentation, and current medications. Clinical presentation was defined as urinary abnormalities (UA), nephrotic syndrome (NS) and acute nephritic syndrome (ANS). Renal diseases were divided into 4 major categories: primary glomerulonephritis (GN), secondary GN, tubulointerstitial nephropathies (TIN) and vascular nephropathies (VN).

From 1977 up to 1987, a mean of 95 +/- 18 renal biopsies/year were performed; this number significantly increased to 185 +/- 22 renal biopsies/year (range 138-200) (p<0.001) in the following period (1988-2005). Renal biopsy was more frequently performed in males (59%) compared with females (41%). Of all diseases of the native kidney, primary GN was the most frequent (66%), followed by secondary GN (25.6%), TIN (4.2%) and VN (4.2%). The type of primary GN with the highest frequency was mesangial GN (both IgA and non-IgA) (45.7%), followed by membranous GN (23%), focal segmental glomerulosclerosis (19.8%), minimal change disease (5.3%), crescentic GN (4.2%) and postinfectious GN (2%). In terms of age, renal biopsy was more frequently performed in patients aged 20 to 60 years, and nearly 60% of patients presented a glomerular filtration rate (GFR) >60 ml/min at the time of biopsy. The main clinical reason for performing renal biopsy was UA, in all the types of nephropathies.

We confirm data that renal diseases are more frequent in men, with the exception of secondary GN. The mean age at diagnosis was 42 years resulting from the tendency not to perform renal biopsies in children and in elderly patients. Renal biopsy was mainly performed in patients with GFR >60 ml/min and asymptomatic urinary abnormalities suggesting concern on the part of clinicians regarding glomerular diseases. The tendency to perform renal biopsies has been significantly increasing throughout our follow-up period.