Causes and consequences of proteinuria following kidney transplantation.

Proteinuria is common following kidney transplantation and affects more than 40% of kidney transplant patients per year. In general, the level of proteinuria is low (<500 mg/day) but even those levels significantly reduce graft and patient survival. This is why it is of vital importance to detect proteinuria quickly following transplantation and to investigate its cause. During the same year of the transplant, proteinuria may be caused by multiple factors, including glomerular disease, effects of anti-HLA class II antibodies and drugs such as mTOR inhibitors, tubulointerstitial disease of the graft, and significant functional discrepancy between the graft and the recipient. The relationship between proteinuria and graft survival is likely to be due to the factors that cause proteinuria. It is unknown why proteinuria and patient survival are related, but it could be due to a relationship between proteinuria and traditional cardiovascular risk factors or a relationship between proteinuria, endothelial function and inflammation. To treat proteinuria, three aspects should be considered: the cause of proteinuria, the non-specific reduction of proteinuria, and the reduction of the cardiovascular risk.