A New Quantitative Classification of Diabetic Nephropathy by Morphometric Analysis

Accessible online at: www.karger.com/journals/nef Dear Sir, The pathological stage of diabetic nephropathy had been traditionally evaluated using Gellman’s criteria [1], on the basis of 4 grades according to the severity of diffuse glomerular lesions. It is generally accepted that the histopathological staging ensures the reliable diagnostic criterion of diabetic nephropathy. However, a wide discrepancy remains among pathologists as to on which basis they discriminate the degree of mesangial area expansion. Therefore, a new quantitative classification of diabetic nephropathy is needed. We attempted to clarify a new histopathological staging of diabetic nephropathy using 30 patients with type 2 diabetes mellitus who underwent renal biopsy (19 males and 11 females, serum creatinine concentrations 0.3–1.8 mg/dl). Tissue specimens obtained by percutaneous renal biopsy were processed for morphometric evaluation by light microscopy. Serial sections 3 Im thick were cut and stained with periodic acid Schiff. The severity of diffuse glomerular changes was graded on a scale of D1 through D4 according to Gellman’s criteria [1] by a single consultant pathologist as follows: D1 (local lesion present within each glomerulus and focal lesion present within the kidney); D2 (mesangial thickening is diffuse within the glomerulus and generalized throughout the kidney); D3 (capillary lumina are narrowed and obliterated only locally); and D4 (the lumen is generally narrowed and the entire glomerulus is ischemic and appears to be hyalinized). The severity of glomerular lesions was also estimated by quantitative morphometric studies [2]. Briefly, PASstained specimens were analyzed using a color image processor (SPICCA-II, Olympus Co., Tokyo, Japan) measuring glomerular area (GA) and mesangial area (MA). The GA was defined as inner area of glomerular tuft outline, and the mesangial rate (MR%) was defined as the ratio of MA to GA. The mean value of MR% was 14.4 B 2.1% in D1, 19.7 B 3.0% in D2, 25.3 B 2.3% in D3, and 35.2 B 2.5% in D4. There Fig. 1. Correlation between the grades of diffuse glomerular lesions evaluated by Gellman’s criteria and mesangial rate (MR%) estimated by computer-assisted quantitative morphometric analysis.