Definition: Proteinuria literally means "protein in the urine." When kidneys are healthy, protein molecules can't pass through the delicate filtration system. When that filtration system becomes damaged, protein can move through the kidneys and shows up in the urine.
Two common causes of proteinuria are diabetes and high blood pressure. Often proteinuria is the first indicator of kidney damage. There are usually no symptoms in the early stages.
A simple urine test can detect proteinuria.
