We all leak tiny amounts of albumin (a protein which has a small molecular size and is water-soluble) into our urine. If the filters in our kidneys are damaged, increased amounts of albumin and other larger proteins from our blood can pass through and escape into the urine.
Definition of aftertaste. : persistence of a sensation (as of flavor or an emotion) after the stimulating agent or experience has gone.
to excrete is to get rid of something from your body. In this case you are probably referring to the end of the gastrointestinal system and possibly the urinary system. Either way, they get rid of wastes in the body that if built up would cause harm to the rest of the body.