#2265 The challenge of renal biopsy in diabetic patients: evaluation of a single center large cohort from North-West Italy
Authors: Fenoglio Roberta , Careddu Andrea , Rabajoli Gianluca , Marchisio Martina , Geraci Giovanni , Morrone Marco , De Simone Emanuele , Roccatello Dario 
Published: May 2024

Abstract

Background and Aims
Diabetic kidney disease is one of the most severe long-term complications of diabetes. Currently, the international guidelines suggest diagnosis of diabetic nephropathy to be achieved on a clinical ground only. However, in the heterogeneous cluster of different conditions putatively co-existing with diabetes, renal biopsy is a unique tool for an accurate diagnosis and a guide for patient management. The aim of the study was to retrospectively analyze monocentric case history of kidney biopsies performed in diabetic patients over a period of 10 years. Patient's data were collected both at the time of histological examination and during follow-up.

Method
Data of renal biopsies (RB) performed in patients with diabetes mellitus from 1st January 2014 to 31th July 2023, were collected. Patient identification was performed by reviewing clinical histories and histopathological charts. Data on the indication for RB were collected from the medical report of the hospitalisation when the procedure was performed or from the visit when the indication was given. Atypical features were categorized according to an adaptation of the 2007 KDOQI guidelines for diabetes and chronic kidney disease.
The significance of baseline differences was determined by the chi-squared test, Fisher's exact test or the unpaired t-test, as appropriate. Significance of univariate analysis were confirmed through the use of multivariate analysis. Correlation analysis, linear regression and Cox regression were also performed. A two-sided P-value &lt;0.05 was statistically significant. All statistical analyses were performed using SPSS version 26.0 (IBM, Armonk, NY, USA).

Results
Among 1990 patients (pts) who underwent kidney biopsy during the study period, 297 had type 1 or type 2 DM (14.9%) and were therefore included in the study, regardless of diagnostic suspicion and histological findings. Histological examination revealed diabetic nephropathy (DN) in 112 cases (group 1), DN associated with another kidney disease in 56 cases (group 2) and nondiabetic renal diseases alone in the remaining 129 cases (62%) (group 3). In group 2 the kidney disease most frequently associated with DN was focal and segmental glomerulosclerosis, FSGS (24/56 pts) followed by IgA nephropathy, IgAN (14/56 pts). In this population the histological examination led to specific therapeutic indications in 22 patients. In group 3 the most frequently observed kidney disease was FSGS (37/112 pts) followed by ANCA-vasculitis (14/112 pts), membranous nephropathy (14/112 pts) and IgAN (10/112). In this population, histological examination led to a specific therapeutic indication in 67 pts. To determine predictors for histopathological diagnosis of DKD, we ran a logistic regression model. The covariates used in this model were the duration of diabetes, presence of retinopathy, hypertension, serum creatinine values, eGFR values and 24-hours proteinuria. None of them was found to be statistically significant. It should also be noted that 47 out of 112 pts (42%) with diabetic nephropathy had no retinopathy. In contrast, 9 pts (7%) with histological evidence of NDRD had diabetic retinopathy. 215 out of 297 pts had a follow-up of at least 6 months. During a mean follow up of 41.6±31.8 months, 53 pts (24 in group 1, 15 in group 2 and 14 in group 3) reached end stage kidney disease (16.5 months). In our population the presence of DN associated with another biopsy-proven nephropathy was especially prevalent. Having double nephropathy conferred a relative risk-RR for dialysis of 1.8089 (95% CI 1.0094 to 3.2415, P = .0464).

Conclusion
To our knowledge this is the largest cohorts of diabetic patients receiving renal biopsy even reported in a Western country. Our data proved kidney biopsy not to be an academic exercise in diabetic pts. Clinical and laboratory features do not predict histologic findings. Renal biopsy allowed the identification of unsuspecting nondiabetic kidney injuries and double nephropathies, which could be susceptible to different outcomes, and paved the pathway for treatment of potentially manageable histological changes.