Kidney biopsy and pathological evaluation
Indications for kidney biopsy in a diabetic patient were active urinary sediment such as dysmorphic erythrocyte, hematuria, erythrocyte, and leucocyte cylinders, the rapid loss of GFR, sudden onset nephrotic syndrome, severe proteinuria, diabetic retinopathy and proteinuria in the absence of other microvascular diseases. A kidney biopsy was performed with a tru-cut needle percutaneously with ultrasonography after obtaining the written consent of the patient.
Kidney biopsy samples were evaluated with light and immunofluorescence (IF). Paraffin-embedded tissues were cut at 3 µm for light microscopy evaluation and routine staining. All samples were stained with hematoxylin and eosin (H&E), Jones methenamine silver, Masson trichrome and periodic acid-schiff, crystal violet, and congo red dyes.
For direct immunofluorescence, the renal tissues were quickly frozen in liquid nitrogen and cut into 3 µm sections. In biopsy samples, antibodies against IgG, IgA, IgM, C3, C4, C1q, fibrinogen, kappa, and lambda were examined. All biopsy samples contained at least ten glomeruli. Glomerular basement membrane (GBM) thickening, mesangial expansion, nodular glomerulosclerosis, arteriolar hyalinosis, and arteriosclerosis were evaluated in renal biopsy specimens for the diagnosis of DN1. Specific histopathological diagnostic criteria were used in kidney biopsy of patients with PGN11. Electron microscopy was used for differential diagnosis only in suspected cases.
Chronic damage in the renal parenchyma was evaluated with interstitial fibrosis and tubular atrophy. Renal parenchymal interstitial fibrosis was expressed as a percent and tubular atrophy as yes/no. All biopsy samples were evaluated by experienced nephropathologist.
Ethical Approval All procedures performed in the study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The ethics committee has approved this study at our university.