Kidney stones grow and dissolve much like geological crystals

It took a close look at crystal formation in Yellowstone’s hot springs to understand stones much closer to home. Growth and dissolution patterns found in rocks there mirror what’s going on with stones in our kidneys, says Bruce Fouke, a geobiologist at the University of Illinois at Urbana-Champaign, contradicting the medical dogma that kidney stones don’t dissolve.

Fouke, who usually travels to hot springs and coral reefs for his research on minerals and crystals, had never seen a stone that “doesn’t grow and dissolve, grow and dissolve.” He teamed up with an interdisciplinary research group for “a good, geological look at a kidney stone.”

Kidney stones are usually composed of calcium and oxalate, which is found in nuts, rhubarb, beets and other foods. Shining ultraviolet light on thin sections of the stones revealed colorful mineral strata and collections of what look like gems. “You actually go from thin layers to these great, big — I know it’s weird to use this word — beautiful crystals,” Fouke says.

The array of hues comes from organic materials — microbes, kidney cells and the chemicals they produce — trapped within the mineral layers, the team explains September 13 in Scientific Reports. Bursts of shape and color map the history of the stone. Bigger crystals dissolve and leave voids that are then filled by new crystals. Fouke suspects that, like the microbes in Yellowstone’s hot springs, kidney microbes may jump-start crystal growth.

It’s unknown why an estimated one in 10 people end up with large, painful kidney stones. But Fouke thinks a better understanding of the stone’s structure and chemistry may lead to treatments to “help a kidney go back to its normal mode of growing tiny stones, but then dissolving them and not flipping back to growth mode.”