How do you know if you need a Liver Flush?!

What is the point of doing a liver flush...How do you know if you need to do one? and how do you go about it? is there something you buy, what do you eat, do you tell your doctor about this? is it recommended by your doctor? I'm really clueless about liver flushing, but would like to know more because I recently read that it's smart to do a Liver Flush before going on a water fast... which is my main focus.
Any help would be appreciated :) thanks & good luck to all... Tweet