Syag, i am pretty sure that there is a difference between liver and kidney because the liver is a regenerating organ so if you remove part of the liver it will regenerate and grow back. It is NOT an easy procedure but it is not a procedure that leaves you without an organ.
On another note, I am truly sorry for your loss, you certainly did everything humanly possible on her behalf. I would also like to wish your husband an Refuah Sheleima. May you have only simcha and nachas in the future.