Any dude who's ever had to pass a kidney stone out of his body has probably thought to himself: There's gotta be a better way. (You would too, if you had to pee out a jagged rock that collected in your kidney.)
It turns out there might be a better way, but there's a catch: It involves throwing your hands in the air, having your body whipped side to side as the Big Thunder Mountain Railroad roller coaster careens through "a haunted gold-mining town"—an oddly fitting detail, as people's kidney stones (less charming but still hard mineral deposits) travel down urinary tracts via some heady combination of gravity, hydraulics, and that unsettling stomach-drop sensation.
Okay, maybe a roller coaster isn't a perfect solution. But still, that's sort of what happened in a particularly thrilling study on kidney stones and roller coasters published in The Journal of the American Osteopathic Association.
Study authors Marc Mitchell, D.O., and David Wartinger, D.O., were intrigued by reports from patients who said they'd passed kidney stones right after riding the roller coaster at Walt Disney World’s Magic Kingdom theme park in Orlando, Florida. One particular patient passed a stone after three consecutive rides; others said theirs were dislodged within hours of leaving the park. Coincidence? Researchers thought not.
To put the coaster's capabilities to the test, they didn't subject men and women with kidney stones to countless go-arounds on the roller coaster. Instead, Mitchell and Wartinger 3-D printed a model silicone kidney using a CT scan of an actual organ, and filled it with urine and real kidney stones. (They tried ballistic gel, but it fell apart too easily; cow and pig kidneys didn't seem the appropriate choice for a family-friendly park.) So they carried their mock kidney in a backpack and brought it onto the ride, positioning it to align with the actual location of someone's kidneys. Then, the researchers subjected themselves to 60 rounds (of, no doubt, unbridled fun), waiting in line after each, and letting staff members seat them randomly on the Big Thunder Mountain Railroad.
During each round, researchers noted the position of the kidney stones and re-positioned any that had become dislodged after each ride. After five dozen tests were completed, the researchers crunched numbers. They found sitting in the front part of the coaster resulted in a passage rate of about 17 percent, while sitting in the back enabled their model kidney to pass a kidney stone about 64 percent of the time. Not bad.
The researchers aren't exactly sure why the roller coaster facilitates kidney stone passage—or if coasters, like buses, subject riders to more force and a rougher ride toward the back. “We know that the moderate-intensity coaster worked," study author David Wartinger told Popular Science. "You don’t need 70-mile-an-hour coasters, you don’t need precipitous drops, you don’t need inversions, you don’t need high speed turns. What I think is happening is we’re vibrating the stones loose."
You don't need to plan a trip to Disney, either. Any roller coaster can do the trick, the researchers say. In fact, once you've passed a kidney stone, regular riding on a moderate-intensity roller coaster may help prevent future stones from forming by helping very small—like, grain of sand-sized—minerals pass through before they get problematically large. This can help the approximately 300,000 patients who seek emergency care for kidney stones in the U.S. each year, the researchers say. And while a guy has only an 11% chance of acquiring kidney stones in his lifetime, getting to an amusement park now and again for a little excitement won't hurt.