The voltage delivering 1 watt depends on how many amps are present. We use watts to measure power (P), and amps (I) times volts (E) equals watts.
The urea and water that make up urine are removed from the blood in  the kidney. This is then passed on to the bladder which will be  excreted as urine.
The urea and water are released from the liver cells to the bloodstream and transported to the kidneys where the blood is filtered and the urea is passed out of the body in the urine.