Every year around Spring Break there is a mass migration in which flocks of families from mid-Michigan flee the winter cold and head South, down to Orlando, Florida and the many theme parks there. They return a week later, satiated with fun and sun, cleansed of their worries by the vacation and their kidney stones by the roller coasters.
Yes, riding a moderately intense roller coaster for just a few minutes might be enough to dislodge those pesky kidney stones before they turn into an even bigger problem. In a paper published today in The Journal of the American Osteopathic Association, researchers showed that riding the Big Thunder Mountain Railroad at Disney World’s Magic Kingdom helped kidney stones dislodge.
Kidney stones are small mineral deposits that form in the kidney and can be very painful to pass through the urinary tract. They can result in about 300,000 emergency room visits in the United States each year, with annual costs of treating kidney stone patients at about $2.1 billion.
Urologist David Wartinger told Popular Science that the idea for the study came about eight years ago, after a patient came to see him after a spring break vacation down to Disney World. The patient had gone on a ride, the Big Thunder Mountain Railroad in Disney World’s Magic Kingdom three times in a row. That, in itself was not unusual. What caught Wartinger’s attention was the fact that after each ride the patient passed a small kidney stone, passing three stones in less than an hour.
“That really caught my attention, there was something going on here with roller coasters and renal calculi [kidney stones]” Wartinger says. “The problem was, how do you study something like that?”
Wartinger and his colleague, Marc Mitchell, tested the idea by using a silicone model kidney filled with urine and real kidney stones, then carrying it onto the ride in a backpack, positioned to align with the actual location of the kidneys. The silicone mold was 3D printed using a CT scan of an actual kidney. The silicone was chosen after thought was given to other options, including ballistic gel (which fell apart after use) and cow and pig kidneys, which the authors note in the paper would have been poor choices “owing to ambient temperature and the inappropriate display of such material in a family-friendly amusement park.”
For the purposes of this study, they rode the Big Thunder Mountain Railroad 60 times with the fake kidney, noting the position of the kidney stones and re-positioning any that had become dislodged after each ride, and standing in line along with everyone else at Disney to determine where on the ride they would sit. They found that sitting in the front part of the ride resulted in a passage rate of 16.67 percent, while sitting in the back resulted in passing a kidney stone 63.89 percent of the time.
The exact mechanisms by which roller coasters help dislodge a kidney stone are still unknown, but Wartinger does have some ideas as to what’s going on. “We know that the moderate intensity coaster worked. 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.” Wartinger says.
But before everyone rushes to Disney World with doctor’s notes, it’s important to note that this was only one model with one set of kidney stones. The interior of kidneys are unique to each person, and kidney stones also grow in many different shapes and sizes, so this isn’t a one-size-fits-all roller coaster solution.
“The recommendation isn’t go to Disney World and ride this one coaster” Wartinger says. “Amusement theme park rides of moderate intensity have the potential to dislodge stones. So whatever coaster or park catches your fancy, you can probably benefit from attending.”
Wartinger says that three types of people could probably benefit the most from a roller coaster prescription: people that have small kidney stones, people that have had an operation to break a larger kidney stone into smaller pieces, and women who have small kidney stones and are trying to get pregnant (vitamin supplements taken with pregnancy can cause kidney stones to grow larger).
If he can get more cooperation from other theme parks, Wartinger hopes to expand the study to look at how other roller coasters affect kidney stones. And it’s not just people here on the ground that might benefit.
Kidney stones are a huge problem for astronauts on long-term missions in micro-gravity environments. While building a roller-coaster in space might be impossible, Wartinger says that it might be possible to build a device that could spin people around, jarring the stones loose, no roller-coaster required.