The kidneys' function is to remove the waste in our blood by acting as filters.
These filters (called glomeruli) prevent the excretion of the protein in the blood. Normal kidneys excrete very small amounts of protein in the urine.
Albumin is the most common protein in the urine.
Persistent increased amount of albumin in the urine (high ACR) is a sensitive early marker of kidney disease. It reflects damage to the glomeruli which causes them to become more “leaky” with subsequent loss of albumin from the blood into the urine - albuminuria.