#1254 Renal biopsy in diabetic patients—25 years of a single center experience

Abstract Background and Aims A significant part of patients with CKD and diabetes mellitus especially of type 2 (DM2T) may have a nephropathy of non-diabetic origin, and renal biopsy (RB) is needed in a differential diagnostics. The aim of this study was to evaluate clinical and laboratory data and the results of RB performed in diabetic patients in our department during a period of 2000–2024. Method Diabetic patients with clinical suspicion of a non-diabetic nephropathy were indicated for RB. In all patients, RB was performed by a biopty gun with ultrasonography control. Obtained specimens were analyzed by the light, immunofluorescence and electron microscopy. Results were evaluated by descriptive statistics and unpaired t-test. Results From 883 of all patients indicated for RB during a period of 2000–2024, there were 131 diabetics (14.8%) including 112 with DM2T, 16 with DM1T and 3 with secondary diabetes. Among them, 77 men and 54 women were present with a median age (range) 58 (20–74) years, duration of diabetes 9.0 (0–33) years, duration of nephropathy 8 (1–264) months, serum creatinine in time of RB 150 (56–1000) μmol/l, and proteinuria 7.8 (0.5–34) g/24 h. Nephrotic range proteinuria was present in 110 (84.0%), hematuria in 79 (60.3%) and hypertension in 118 (90.1%) diabetics. Histological diagnosis was established in 125 (95.4%) patients and a mean amount of glomeruli in a specimen (for all 3 methods of analysis) was 30 (0–83). In 47 (37.6%) patients, a typical diabetic nephropathy (DN) was diagnosed, while in 78 (62.4%) other nephropathies were present either alone in 59 (47.2%) patients or in combination with DN in 19 patients (15.2%). Among single non-diabetic nephropathies, membrane glomerulonephritis (GN) in 23, systemic lupus or vasculitis associated GN in 10 and IgA nephropathy in 6 patients were the most common. In combination with DN, nephroangiosclerosis in 5, IgA nephropathy in 4 and membrane GN as well as minimal change disease in 3 patients were the most frequent. Patients with typical DN did not differ from others in terms of duration of nephropathy, serum creatinine, proteinuria or hematuria, but were of significantly lower age (53.1 vs 58.5 years, p<0.02), longer diabetes duration (14.3 vs 7.6 years, P < 0.001) and had a diabetic retinopathy more frequently (26 vs 3 patients, P < 0.001). Diabetic retinopathy had a high specificity (96.2%) and positive predictive value (89.3%) as a marker of DN. In one patient with a combination of DN and nephroangiosclerosis of stage G4A3, RB was complicated with a large hematoma and nephrectomy. Conclusion Up to 62.4% of diabetic patients indicated for RB had a nephropathy of non-diabetic origin (either alone or combined with DN). Clinical and laboratory data were of no value in differential diagnostics except for age, diabetes duration and diabetic retinopathy. Properly indicated RB is a valuable tool for the assessment of precise diagnosis, prognosis and focused therapy in these patients.