EDIT: Please read my Nearly 3 Years Later: 3 Broken Bones & 200+ Pounds - The Long-Term Effects of Juice Fasting update before considering juice fasting. I hope that my experience will provide you with real-world information about long-term juicing.
Liver/gallbladder flushes are one of the hottest trends for those who do detoxes, and I must admit that I tried it. Yes, I did expel what looked like "stones". However, since I never leave a stone unturned (tacky, I know), I used a tool to place one onto something to examine it. I used the tool to press it, and what do you know? It completely disintegrated and was very oily.
Here's what I know: The Epsom salt flush was a horrendous experience for me. My kidneys took a beating and they were sore for a day or two. Do not do this "flush"!
For a more scientific explanation of this trendy flush, read Why You Should Never Do a Liver Flush.