It seems so far no one has an answer. I can only guess, it used to say on Master-Cleanse that you could get gallstones, it might not be there anymore. Though the Master-Cleanse also seems to be an Ayurvedic cleanse Andreas Moritz told me not to do it because of my body type (Pita). As far as flushing you should not do just one but up till to 8 at least. I would suggest to go to Ask Andreas Moritz archived forum and search yellow eyes. Also try Liver Flushing there is a lot of information on that forum.
When you are there you can click at the bottom of Andreas post and scan all his messages. Also search Oxypowder because you can do a Bowel Cleanse at the same time between flushes.