A simple mechanism to understand Stone Formation
Imagine a glass of water containing little salt .If you add some more salt, it dissolves. When you add more and more salt, a stage is reached when the water is no longer able to dissolve the salt added to it. This is because the solution is supersaturated with the salt.Above this point , any little amount of salt added to the solution will start precipitating. This is exactly the mechanism by which stones form except that the solution is urine and the chemical composition of the salt is different. There are 3 main ways by which stones form in the urinary tract.
First a crystal has to form, then it has to grow and then a large number of such grown - up crystals has to aggregate to each other before it becomes large enough to block the urinary passage.
It would be comforting to know that nature has it own protective mechanisms to prevent stone formation. Yes ! there are certain substances in urine which interfere with the growth and aggregation of crystals which are responsible for stone formation.It is because of the presence of these substances in urine that most of us do not form stones. The stone forming substances are kept in a dissolved state in our urine.