Kidney stones are made of salts and minerals in the urine that stick together to form small "pebbles." They may form when the normal balance of water, salts, minerals, and other substances found in urine changes. How this balance changes determines the type of kidney stone you have. Most kidney stones are calcium-type-they form when the calcium levels in your urine change.
Current as of: May 1, 2026
Author: WebMD Ignite Staff
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