A few years ago, two Michigan urologists noticed a curious pattern among their patients: Upon returning from a Disney World vacation, patients would report they had passed a kidney stone after riding Big Thunder Mountain Railroad. (Yes, seriously.) Now the doctors are actually studying the phenomenon — complete with their own, um, interesting trip to Disney World — and they've turned up some surprising results, The Atlantic reports. Approximately 10% of people will get kidney stones (small mineral deposits in the kidneys) at some point. Although most people pass them through the urinary tract without any noticeable issues, some stones become large enough to cause a ton of pain when they exit. (The pain of passing stones is often compared to that of childbirth.) That, plus the unpleasantness of bloody urine and also nausea, often sends people with kidney stones to the ER. So, being able to prevent these stones (usually by drinking enough water every day) — or at least getting them through your system before they get that big — could save you pain as well as money spent on healthcare. It could even preserve your sanity. For the study, forthcoming in the October issue of the Journal of the American Osteopathic Association, the researchers managed to take a model of a kidney (tucked safely into a backpack) that was full of real, diluted pee on Walt Disney World's Big Thunder Mountain in Orlando, FL. The researchers decided that if the fake kidney's fake kidney stone was dislodged and made it to the fake ureter (where urine normally passes from the kidney to the bladder), that would count as "passing" the stone.
After 20 rides, they found that the coaster could, indeed, send the stones on their way. However, the results were significantly different depending on where they sat on the coaster. If they were near the back, where the coaster's twists and turns may be a bit stronger, 64% of the stones were dislodged. But if the researchers were up front, only 17% of stones were passed. Of course, the next step for the researchers is an actual clinical trial, which may someday down the road lead to some exciting new treatments for kidney stones. Right now, though, there's no reason to go out of your way to hop on a coaster if you're worried about those stones — and this definitely doesn't apply to the ones that are already causing pain. But it does suggest that your next trip to Space Mountain could come with an unexpected surprise.