Different patterns of renal damage in type 2 diabetes mellitus: a multicentric study on 393 biopsies

The frequency of various types of renal changes in patients with type 2 diabetes is not clearly defined in the literature. Reported discrepancies likely are caused by ethnic and geographic factors. However, policies used in nephrological centers for the selection of patients to undergo renal biopsy also may have an influence. The present study reports 393 renal biopsies in patients with type 2 diabetes performed in a group of centers in northwestern Italy using different (restricted [CRPs] or unrestricted [CUP]) biopsy policies. On the basis of light microscopic, immunofluorescence, and ultrastructural findings, cases were subdivided into three classes characterized by the presence of diabetic glomerulosclerosis (class 1), prevailing vascular (arterioarteriolosclerotic) and ischemic glomerular changes (class 2), other glomerulonephritides superimposed on diabetic glomerulosclerosis (class 3a), or glomerulonephritides without the presence of diabetic glomerulosclerosis (class 3b). Although no significant differences were found for class 2 (detected in 15% and 16% of patients from CRPs and the CUP, respectively), the frequency of the other two classes was strongly biased by the biopsy policy. Class 1 was found in 29% and 51% of cases, and class 3 in 57% and 33% of cases from CRPs and the CUP, respectively. Moreover, class 3a was more common (67%) in the CUP, and class 3b (78%) in CRPs. Our findings may explain conflicting data from the literature and the influence that type of adopted biopsy policy may have on an epidemiological evaluation. This study helps clarify the frequency of renal changes in patients with type 2 diabetes and suggests more extensive use of renal biopsy to obtain reliable prognostic indications and plan a rational therapeutic approach.