A practical approach to proteinuria.

Proteinuria is defined as urinary protein excretion exceeding 150 mg/day. It may result from nonpathological (posture, fever, exercise) or pathological (glomerular or tubular) processes. Glomerular proteinuria is an early sign of kidney disease and may also play a role in the progression of glomerular damage. Asymptomatic proteinuria is common; it may be transient or persistent. Transient proteinuria is a benign condition and requires no evaluation. Persistent proteinuria can be the first sign of kidney disease. Persistent proteinuria commonly results from disorders associated with increased glomerular permeability such as nephrotic syndrome, glomerulonephritis (e.g., post-infectious, membranous, membranoproliferative, lupus, IgA), and genetic defects (Alport syndrome, mesangial sclerosis). Tubular disorders should also be considered. Evaluation for the underlying cause is traditional. Whether the early detection and evaluation of proteinuria prevents progressive disease is unknown.