The general wisdom is that it takes 5 or 6 before seeing any results but be prepared to do at least a dozen or so before you stop passing stones. It took me 18 flushes before the all clear.
For me it's hard to judge what was doing what after my first 40 day MC. I was a man on a mission and was doing all kindsa things including exercising 5 to 7 days a week and eating a pristine diet of nothing but raw organic foods and lots of fresh made veggie juices.