They also help keep water inside tiny blood vessels. Proteinuria is the name of a medical condition. It means protein is in the urine. As blood moves through the kidneys, the kidneys filter out waste products, excess fluid and salts. The clean blood cycles back through the body.
Most proteins are too big to go through the kidneys, so usually no protein is found in urine.
Sometimes infection or toxic chemicals damage the kidneys, and this makes protein show up in the urine. Dipping a special strip of paper into a sample of urine tells your doctor if protein is in it. Your doctor might do a few other tests to make sure. Your doctor may ask you to collect a 24-hour urine sample from your child. Directions for doing this are at the end of this handout.