I'm no expert on this, but will share my own experience. I was doing a lot of fasting/bowel cleansing, but I think I did some a little too fast (or not enough colonics?) and after felt some strain on my kidneys. So, given my experience, I would start with bowel cleansing. If you're colon is not clean, the excess toxins can end up in other organs...in your friend's case, that could cause serious complications!
I'd check out the Richard Schultze link at the top of the page.
That's my experience, maybe others have better input.