Milk thistle for your kidney's ?? Never heard of that. I thought it helps repair the liver by restoring liver enzymes. It is supposed to protect your liver from toxins while it stimulates liver cell synthesis. You will want to get milk thistle containing Silymarin which helps to blockage of toxins entering the liver cells, it increases the antitoxidant activity in the liver cells and stimulates protein synthesis.
Never tried the Liver Detox Factor but I have heard great feed back on it. Plus, if you have to get a prescription for it, chances are its the real deal....