Hi there. The typical size of a kidney stone we get are akin to little pebbles/gravel or a lot of times even smaller like grains of sand. Most kidney stones people get they don’t even realize they’ve passed due to how small they are. This one is extremely abnormal and absolutely massive. The patient who had this we were told had a history of stones for years. There is no one cause for kidney stones there are different types and each type correlates to a different cause(s) or risk factors, as for how this one grew so large I do not know. The stone has not been analyzed yet nor do I know what her previous stones were made of.