[Incidental finding of proteinuria].

A positive signal when testing urine for proteinuria is a frequent finding, either in the context of a routine medical check-up or when searching for a specific renal disorder. This brief overview aims to provide assistance in the classification of proteinuria and to provide guidance to the next diagnostic and therapeutic steps. The normal urine protein loss of a healthy adult is less then 150 mg/day. Higher rates of proteinuria should be confirmed as this is often a sign of glomerular or tubular damage. In addition, proteinuria is a strong prognostic factor for cardiovascular and total mortality. Principally, proteinuria is 1) a symptom of renal diseases, 2) a progression factor for renal diseases and 3) a risk factor for cardiovascular diseases and total mortality. In this article proteinuria is defined, the correlation to various renal diseases is described and the relevance for progression of renal diseases and total mortality is shown. Finally, diagnostic procedures are described and a perspective on therapeutic measures is provided.