Lets start at the beginning. The so-called Kidney Stones are not always located inside the kidneys. In fact, most of them are outside it, either in the ureteropevic (that's the junction area between kidney and ureter), in the middle of the ureter tract, just as the ureter is crossing the iliac artery, or just before entering the bladder. Why? Because those three areas are where the diameter of the ureter are smallest.
Now, if you read on the article title, you'l probably wondering "but those aren't how kidney stones are formed!" Well OK, kidney stones are in fact made from the itty bitty things that are contained in your urine. More specifically, there are several causes to a kidney stone, such as increased urine calcium or uric acid concentration, infections, and lack of magnesium in the urine. Normally all those doesn't cause any trouble, but when something cause them to precipitate into crystal, things begin to get interesting. Now I can't write all the contents of the textbook, they'll expect me to pay for it. But I can tell you that the crystal serve as the nidus, or core, of the stone. Therefore when you have to have one of those PNL (percutaneus nephro litholapaxy), they will cut the stone to see what is the nidus is composed of, and therefore knowing what kind of diet you are to go on, either low calcium, low protein, hi magnesium etc. But we don't need to know too much about that. Just know that adequate intake of water (that's drinking water, kids), and regular voiding (and that's peeing, isn't it fun?) is what most people need to do to avoid the unwanted stones.
