Your kidneys are located near the middle of your back, on either side of your backbone (spine). They are protected from physical injury by a large layer of fat, along with your lower ribs and back muscles.They are bean-shaped, and each one is the size of an adult fist (about 150 grams). Most people are born with two kidneys, but around one in every 750 people are born with just one. The good news is that you can still lead a healthy life with just one. One kidney alone can provide up to 75 percent of normal kidney function.The entire organ is not one big filter. Each kidney is made up of about one million tiny filters called nephrons. Blood enters your kidneys through the renal artery and goes back into your body by the renal vein.