Cardiovascular disease remains one of the major cause of mortality in renal transplant recipients, with the rate of cardiac death 10-times higher than that of the general population. An independent association between post-transplant proteinuria and cardiovascular risk has been previously reported. Diseased native kidneys with residual urine output or the transplanted kidney could be the source of proteinuria following renal transplantation. A clear differentiation of the source of proteinuria (native kidneys versus allograft) could be important for appropriate management. Proteinuria from native kidneys falls rapidly after renal transplantation, and persistent or worsening proteinuria is usually indicative of allograft pathology. The mechanisms behind the resolution of proteinuria of native kidney origin in the early post-transplant period are not well described. An association between vascular parameters of the macrocirculation and post-transplant proteinuria has been described. To the best of our knowledge no data is available describing a link between post-transplant proteinuria and vascular parameters of the microcirculation. In this study our goal is to analyze in a clinical trial in patients with end stage renal disease and residual urine output the relationship between proteinuria and renal perfusion of native kidneys before and after renal transplantation. In addition the investigators analyse if pre or post-transplant proteinuria is associated vascular and circulatory changes in the retinal circulation. Our hypothesis is that renal perfusion of native kidneys correlates with early post-transplant proteinuria. Moreover the investigators hypothesize that post-transplant proteinuria is associated with vascular remodeling processes of the microcirculation 2 and 4 to 12 months after transplantation. To prove this hypothesis the investigators aim to include 25 pre kidney transplant patients of our living donor kidney transplantation program. Total duration of this study for each patient is 5-12 months with total 4 visits, of which all are performed at the Clinical Research Center of the Department of Nephrology and Hypertension, University of Erlangen-Nuremberg. This study is important to better understand the mechanisms behind the fall of proteinuria after renal transplantation and the association between post-transplant proteinuria and cardiovascular risk.