While healthy kidneys do not allow a significant amount of protein to pass through their filters (glomeruli), filters damaged by kidney disease may let proteins such as “albumin” leak from the blood into the urine. Normally, blood passing through the kidneys has its waste products filtered out and excreted in the urine, while important proteins are retained. Unless the kidneys have been damaged, most proteins are too large to pass through the glomeruli. Albumin, which is smaller than many other proteins, is much more likely to escape through the glomeruli, making it the major type of protein detected in the urine. Abnormal amounts of protein in the urine, referred to as “proteinuria,” may indicate diabetes, hypertension, or a kidney disorder.
P.S. When large amounts of protein escape through your urine, you may notice symptoms such as foamy, frothy, or bubbly-looking urine as well as swelling in your hands, feet, abdomen, or face.