What does proteinuria indicate in kidney disease?

Proteinuria, the presence of excess protein in the urine, is a significant clinical indicator of kidney damage or disease. In healthy individuals, the kidneys filter out waste while retaining essential proteins; however, when the kidney's filtering units, known as glomeruli, are damaged, they may allow proteins to leak into the urine. This can occur due to various conditions affecting the kidneys, including glomerulonephritis, diabetic nephropathy, and hypertension, among others.

The presence of proteinuria typically suggests that there is an abnormality in the kidneys, reflecting an underlying pathological process that needs to be investigated further. Therefore, in the context of kidney disease, proteinuria is a critical marker prompting healthcare professionals to evaluate kidney function more thoroughly and assess potential damage sustained by the renal structures.