The role of kidney biopsy in deciphering diabetic versus non-diabetic origin of kidney disease among patients with type 2 diabetes mellitus and nephrotic range proteinuria: A retrospective study.

ABSTRACT

Background: Diabetes mellitus (DM) is tightly associated with the increased prevalence of diabetic kidney disease (DKD). Nonetheless, severe renal function impairment and/or nephrotic range-proteinuria could also result from non-diabetic renal disease (non-DRD) among patients with DM. The 'Gold standard' for the differential diagnosis between DKD and non-DRD is kidney biopsy, although no real consensus exists. Thus, this study intends to associate the clinical and biochemical profile of patients with DM and renal disease with the histopathological data of kidney biopsy.In addition, we aimed to evaluate the role of kidney biopsy, especially when other causes, other than DM, are highly suspected among patients with DM and kidney disease. Methods: Thirty two patients with T2DM and nephrotic range levels of proteinuria or with co-existing factors pointing towards a non-diabetic origin of kidney disease were studied, retrospectively. All 32 patients underwent kidney biopsy and were classified according to histopathological findings into 3 groups a) isolated diabetic kidney disease (DKD), b) non-diabetic kidney disease (NDKD) and c) mixed kidney disease (MKD). Results: Fifteen out of the 32 patients had findings of an isolated DKD, while 17 out of 32 patients suffered from NDKD (13 patients) or MKD (4 patients). DKD patients were younger (p = 0.016) and had a higher HbA1c value (p = 0.069, borderline statistical significance), while the NDKD patients had significantly shorter disease duration (p = 0.04). Furthermore, the incidence of diabetic retinopathy (DR) was lower among the NDKD patients (p < 0.001), who had also significantly less interstitial fibrosis (p = 0.02). Finally, the presence of DR, higher levels of interstitial fibrosis and longer T2DM duration were recognized as factors, which were positively associated with DKD. Conclusion: This study advocates the usefulness of kidney biopsy in patients with T2DM and nephrotic range levels of proteinuria, especially when DR is absent and shorter disease duration is observed.