What organ filters waste?
The kidney filters waste.
The correct answer is twofold. The liver filters some substances and metabolizes or breaks them down into byproducts. These byproducts or waste will then be filtered by the kidneys in varying degrees. Which means that not everything that passes through the kidneys comes out in the urine. A percentage of necessary things are needed by the body such as proteins, sodium, potassium and other elements which are essential to the running of the body.
The kidneys are the "filters" of the human body. First, the blood caries Oxygen and glucose to the cells and takes waste materials away from them. In the next step the kidneys filter out(in there nephrons) all the waste the blood carries from the cells. The waste(urine) is stored in the bladder and when full, gives you the "I gotta pee" feeling.