Non-Diabetic Kidney Disease in Type 2 Diabetic Patients: Prevalence, Clinical Predictors and Outcomes.

ABSTRACT

BACKGROUND/AIMS: Diabetic kidney disease (DKD) is one of the most frequent microvascular complications of diabetes and is the leading cause of end-stage kidney disease worldwide. In patients with diabetes, non-diabetic kidney disease (NDKD) can also occur. NDKD can be either alone or superimposed with the DKD. In this study, we aimed to investigate the utility of kidney biopsy in patients with type 2 diabetes mellitus (T2DM) and the predictability of diagnosing DKD versus NDKD from clinical and laboratory data. We also evaluated the prevalence and etiology of NDKD in patients with T2DM. METHODS: We retrospectively reviewed type 2 diabetic patients who had kidney biopsy in the last 10 years for diagnosing possible NDKD in our center. In all patients kidney biopsies were performed because of atypical clinical features and biopsy samples were examined by light and immunofluorescence microscopy. Clinical parameters, laboratory workup and office blood pressures were recorded for each patient at the time of biopsy. RESULTS: Eight patients were excluded due to missing data. A total of 48 patients (female/male 26/22 and mean age 59±8 years) were included in the study. According to the biopsy findings, 24 (50%) patients had NDKD alone, 20 (41.7%) had DKD alone and 4 (8.3%) had coexisting DKD and NDKD. The most common NDKD diagnoses were membranous nephropathy (29.2%), tubulointerstitial nephritis (20.8%) and IgA nephropathy (12.5%). There were no significant differences in three groups with respect to the duration of diabetes, proteinuria, hematuria and glycated hemoglobin A1c levels. Diabetic retinopathy (DR) was the most significant finding, which was associated with DKD. Positive and negative predictive values of DR for DKD were 88 and 81%, respectively. CONCLUSION: This study demonstrated a high prevalence of NDKD in patients with T2DM. The absence of DR strongly predicted NDKD. Clinical decision alone can lead to wrong diagnosis and delay in appropriate therapy. Clinicians should consider the kidney biopsy more liberally when there is uncertainty on the exact etiology of the kidney disease. However, prospective multicenter studies are needed to clarify the prognosis and outcomes of patients with diabetics.