Diabetic kidney disease is the main cause of end-stage kidney disease. However, the clinical manifestations of diabetic kidney disease are diverse. Therefore, the clinical classification of diabetic kidney disease is clinically important and valuable. In Japan, two clinical staging systems divided by the estimated glomerular filtration rate (eGFR) and albuminuria can be used for diabetic kidney disease: the chronic kidney disease (CKD) risk classification and the Japanese classification of diabetic nephropathy. The Japanese classification of diabetic nephropathy and the CKD risk classification are similar; however, these two classification systems show different frequencies of outcomes. For example, the frequency of the kidney outcomes in stage 4 of the Japanese classification of diabetic nephropathy was found to be higher than that in the red stage of the CKD risk classification (composite kidney events: stage 4=32.0/100 person-years, red =14.5/100 person-years). However, there were no marked differences in the speed or rate of decline in the kidney function (speed: stage 4=6.8 mL/min/1.73 m2/year, red =5.8 mL/min/1.73 m2/year; rate: stage 4=38.8%/year, red =34.3%/year) or in the pathological changes between the two classifications. These data indicate that each stage of these clinical classification systems has characteristic clinical and pathological features. Therefore, it is important to understand each characteristic feature and use each classification system appropriately.
Keywords: Japanese classification of diabetic nephropathy; biomarker; biopsy; chronic kidney disease; diabetic nephropathy.