Ten years ago this fall, two Michigan doctors rode Big Thunder Mountain Railroad at Walt Disney World again and again with a 3D-printed kidney hidden in a backpack, testing whether the rattling ride could knock kidney stones loose. In their model, it often did, especially from the back of the train.
The experiment drew laughs and, eventually, an Ig Nobel Prize. But the idea behind it, that small stones and fragments can sometimes be nudged free before they cause trouble, has since taken a more clinical form. In 2024, the FDA authorized an ultrasound device built to push leftover stone fragments toward the exit, and its maker has since won clearance for a second device that breaks stones apart with sound.
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