Association of diabetic retinopathy and renal function in patients with Types 1 and 2 diabetes mellitus

Aims: It takes years for microvascular complications in diabetes mellitus such as diabetic retinopathy (RP) and nephropathy (NP) to develop. Since retinlal and renal vessels are exposed to the diabetic milieu, it is often assumed that progression of 1 diabetic RP and NP occurs at the same time. However, smaller studies have demonstrated that this may not always be the case. The present study was undertaken to correlate dial etic retinopathy with parameters of renal function in a tients with large ambulatory collective of pa Types 1 and 2 diabetes. Methods. The study design was cross-sectional. Ambulatory patients from a large university out-patient clinic were studied (323 patients wit Type 1, 906 patients with Type 2 diabetes 1). P status was obtained through retinal photography by an experienced opthalmologist and was grouped into no RP, RP Stages 1 - 3, or blind. Retinal pathology was correlated with clinical parameters of renal function (proteinuria, estimated glomerular filtration rate according to the MDRD formula, presence of urinary sediment abnormalities, hyperte I nsion). Results- No patient showed urinary sediment abnormalities (e.g. presence of h. 6aturia or acanthocytes) or increased urinary excretion of inummoglobulin light chainsi suggesting the absence of other nondiabetic renal diseases. The majority of Type I di abetes patients with macroalburninuria (>= 200 mg/l) had some signs of RP independent of the presence I elation beof hypertension. There was a cov tween RP and microalburninuria (r = 0. 164, p < 0.01). In contrast, up to 47.5% of the hypertensive patients with Type 2 diabetes and overt proteinuria had no signs 0 RR There was also discordance of microalburninuria and RP in patients with Type 2 diabetes. Stratification according to K/DOQI States 2 - 5 (MDRD formula) showed that the majority of patients with Type 1 diabetes in states 3 - 5 had signs of RP, albeit the absolute number of patients in these K/DOQI stage's was very small. In contrast, up to 40% of dialysis-de-pendent Type 2 diabetics (K/DOQI State 5) showed no evidence of RP. Conclusions: This study revealed that many patients with Type 2 diabetes and renal abnormalities (proteinuria and/or renal insufficiency) showed, in contrast to Type 1 diabetics, no signs of RP. Our study was, however, limited by the lack of renal biopsies. Although urinary sediment analysis was normal in these patients, other causes for renal insufficiency (e.g. vascular nephropathy), especially in Type 2 diabetics, cannot be excluded. Nevertheless, we believe that absence of RP in patients with Type 2 diabetes does not imply that renal abnormalities including diabetic nephropathy, are also absent. It is recommended that these patients undergo renal biopsy.