Thanks for the reply! My dad had stones made of calcium oxalate. The Dr told him to increase his water intake and lower salt in food, which he followed prudently only for a few months. I have done some research regarding how I could prevent them and I've found that, apart from drinking copious amounts of water and lowering salt, I should avoid vegetables that are high in oxalate. Vegetables like spinach, rhubarb, sweet potatoes are what I'm trying to avoid. What I'm afraid about is the hereditary risk.