Dr. David Wartinger is one of the researchers who led the study, which involved bringing a silicone model packed with kidney stones and urine on Walt Disney World's Magic Kingdom Big Thunder Mountain Railroad ride.
Yes, it is as fascinating as it sounds.
Wartinger, an osteopathic urological surgeon and professor at Michigan State University, said he got the idea from a patient who said he passed three kidney stones while riding the Orlando coaster.
"It's hard to ignore that kind of a story, no matter how much of a cynic you are," Wartinger said.
To be fair, you can't pin this one on Disney magic. "We have been hearing stories for years from people who went on vacation, gone to amusement parks, and ended up passing a kidney stone," he said.
First, get a kidney
In order to test this theory, Wartinger and his research partner, Dr. Marc A. Mitchell, had to somehow get a kidney onto an amusement park ride. Since brandishing actual organs for this purpose would probably be frowned upon, they decided on an anatomically accurate silicone mold.
"Our model duplicates the hollow spaces that are in the human kidney," Wartinger said. "The human kidney is the size of a fist and has passageways like branches on a tree. It's in these passageways that kidneys form stones."
Wartinger and Mitchell then inserted urine and kidney stones into the passageways, put the whole thing in a backpack and strapped it in, kidney-height, between the two of them on the ride.
(For the record, while the study was not supported by Disney in any way, the pair got full permission from park officials to do the tests. "We were two grown men carrying a backpack, riding a ride over and over again," Wartinger said. "We definitely wanted to make sure we presented ourselves to park officials beforehand.")
Then, get a thrill
By marking where the stones originally were in the clear kidney model, Wartinger and Mitchell could see how the stones traveled during the ride. In their initial study, they found that seats near the back of the coaster produced better results, where about 64% of the stones successfully passed through the kidney.
The original study featured results from 20 turns on the ride. However, Wartinger says he and Mitchell have conducted an expanded study during which they and their silicone kidney endured the ride more than 230 times. The findings held up, and they observed nearly a 70% overall pass rate.
Why it could work
"There's nothing fancy, nothing difficult to understand," Wartinger said when asked how the whole thing works. "This is just a very mechanical phenomenon. Basically, a kidney stone is a rock. And it is lodged in the physical passageways inside the kidney. It's simply about finding the right amount of shaking and rattling to get it through" to the bladder.
As brutish as it may seem, this is actually in line with some common non-surgical treatments.
"We have tried to suspend people, invert them, pound on their back, administer very high volumes of fluid" to get the stones to pass, Wartinger said. "All have worked with variable amounts of success."
For larger or more stubborn stones, Wartinger says, breaking up or removing the stone through surgery is sometimes necessary.
"Sometimes, when a kidney stone gets stuck, we need to reach up through the urethra and manually grab the stone and pull it out."
To anyone who's ever passed a kidney stone, we apologize for the flashbacks.
Who it could help
Wartinger says he and Mitchell have collected enough data that they are comfortable recommending this "roller coaster therapy," if you will, in certain situations.
Wartinger says it would especially help people with smaller stones. "The idea is, you want to pass them when they are little, not when they are big. If you have a stone that's 4 millimeters or smaller, it should be able to pass without needing surgery and without too much discomfort."
Similarly, those who have had lithotripsy, a procedure to break up kidney stones, may find the jostling helpful in passing fragments that are left behind.
Dr. John G. Pattaras, director of Emory urology services and chief of urology at Emory Saint Joseph's Hospital, said it makes sense that sudden movements can shift kidney stones to help them pass. "Stones commonly lie in the lower pole of the kidney and have to move up to the middle of the collecting system in order to attempt to pass."
There is a precedent. "I have had patients on roller coasters, elevators and hit speed bumps all have acute renal colic (pain) as the stone is moved into a location where it can work its way down the ureter (drainage tube)," Pattaras said.
That doesn't mean roller coasters are going to become part of standard treatment.
Dr. Elizabeth Kavaler, a urology specialist at Lenox Hill Hospital in New York City, said the idea makes sense conceptually, "but practically, no." Roller coaster rides have never been on her list of patient to-dos.
"It's an amusing article, but I can't really tell how it's going to impact my practice or help me with patients. I think it's pretty crazy," Kavaler said. "Whether or not they need to go on a roller coaster seems a little extreme to me."
What else it can tell us
For the researchers, the experiment had significance far past just rattling kidney stones out like a pinball. "Passing a kidney stone is no joy," Wartinger said. "You can't imagine the pain we're trying to prevent through something that's fun."
Not to mention, each kidney stone that's shaken out is one less stone left to grow and possibly pose more complex health problems. "We try to get our (medical) students to think about prevention as opposed to what medicine we can give or what procedure we can do," Wartinger says.
It is also a great parable of doctor-patient communication. After all, Wartinger and Mitchell got the idea from simply listening to their patients' stories.
"If we hadn't talked to our patients, we never would have discovered this," he said.