Clinical implications of pathologic diagnosis and classification for diabetic nephropathy
Introduction
Diabetic nephropathy (DN) is one of the most common causes of end stage renal disease (ESRD) worldwide [1], [2]. Among type I diabetic patients with typical presentation of long duration of diabetes mellitus (DM), the presence of retinopathy, previous microalbuminuria without sudden onset of heavy proteinuria, no hematuria, and non-small-sized kidney, the nephropathy is usually diagnosed as DN in more than 95% of patients [3], [4]. However, the nature of kidney disease in type II DM is more complex. The prevalence of non-diabetic renal disease (NDRD) with or without pure DN is reported as up to 27–79% in type II diabetic patients with nephropathy [5], [6], [7], [8], [9], although it is much lower in studies with unselected protocol based biopsy [10], [11]. Diabetic patients undergo diagnostic renal biopsies only when the clinical course is not typical for DN, and therefore a wide range of NDRD may be present [12]. There are few reports about the influence on renal survival of renal pathologic diagnosis of type II DM with nephropathy, especially in Asian populations [9], [13]. Therefore, challenges remain in the differentiation of NDRD from DN and the verification of the usefulness of pathologic diagnosis to predict renal prognosis in type II DM.
Recently, a uniform and easily applied classification for DN to discriminate various prognostic severities was proposed by the Research Committee of the Renal Pathology Society [12]. Pathologic classifications lead to better communication between renal pathologists and clinicians, provide a logical structure for prognostic and interventional studies, and improve clinical management and efficiency [14]. The results of previous studies [15], [16], [17], [18] that tried to classify DN are useful for research biopsies but are not practical for clinical use [12].
In this study, therefore, we try to determine the prognostic role of the pathologic discrimination of DN and NDRD and the classification system of DN proposed by Tervaert et al. [12] in type II DM with renal biopsy.
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Patients and clinical parameters
This study was approved by the institutional review board of Seoul National University Bundang Hospital (IRB approval number: B-0409/012-003). The study subjects were type II DM patients, as defined by the American Diabetes Association [19], with renal biopsy performed in Seoul National University Hospital and Seoul National University Bundang Hospital between January 2000 and December 2007. Of 142 patients with the absence of keto-acidosis who were identified, 16 diagnosed with DM prior to 30
Pathologic diagnosis of nephropathy in DM
We enrolled 126 diabetic patients having renal biopsy from January 2000 to December 2007. Their mean age at biopsy was 59.9 ± 10.8 (33–81) years and the number of male patients was 86 (68.3%). The mean duration from diagnosis of DM to renal biopsy was 8.3 ± 7.2 (0.1–35.0) years and the mean age at diagnosis was 51.6 ± 10.9 (30–75) years. The pathologic diagnosis was 50 DN, 65 NDRN, and 11 Mixed. IgA nephropathy (IgAN) was the most frequent form except DN. IgAN was present in 9 NDRD patients and in 7
Discussion
The study results revealed that NDRD with or without DN was identified in 60.9% of type II diabetic patients with nephropathy by renal biopsy. The well-known predictors for the presence of DN were also evident in this study but we could not fully discriminate between DN and NDRD with the factors of diabetic retinopathy, DM duration, and age at renal biopsy. Pathologic diagnosis of NDRD was an important prognostic factor for ESRD progression. For pure DN, the pathologic classification correlated
Conflict of interest
The authors declare that they have no conflict of interest.
Acknowledgment
The results presented in this paper have not been published previously in whole or part, except in abstract format.
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