The kidneys normally filter out large molecules from the urine, so albuminuria can be an indicator of damage to the kidneys. It can also occur in patients with long-standing diabetes especially type 1 diabetes.
The amount of protein being lost in the urine can be quantified by collecting the urine for 24 hours, measuring a sample of the pooled urine, and extrapolating to the volume collected. Causes of albuminuria can be discriminated between by the amount of protein excreted. The nephrotic syndrome usually results in the excretion of about 3.0 to 3.5 grams per 24 hours. Nephritic syndrome results in far less albuminuria.
Microalbuminuria can be a forerunner of diabetic nephropathy.