does the kidney filter blood
Basically, the liver does most of the biochemistry in your body, and since it uses the blood stream as a means of transporting things with the rest of the body, must filter it in order to grab all of the things it needs to work with. The kidneys filter blood in a drastically different way. They let small stuff fall out of the blood randomly into them. Then, they decide whether the randomly fallen-out molecule is useful or not. If it is, they pull it back into the blood.