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SYFY WIRE Bad Astronomy

Passing a Kidney Stone Can Be a Real Roller Coaster Ride

By Phil Plait

Update, Oct. 3, 2016: Well, as I feared (and wrote about at the bottom of this article), the research I cover below is pretty shaky. As my editor Susan Matthews here at Slate wrote, this research is interesting, but at best preliminary, and could use a lot more work to be anywhere near rigorous. It's certainly worth following up on (as I also note), but it's nowhere close to being a "cure" for kidney stones as some outlets wrote. I tried to be as noncomittal as possible when I wrote this article, and I hope I didn't lead anyone astray. Next time, when I cover a new medical story that sounds too good to be true, I'll run it by Susan first!

I am not a doctor. Well, I am, but not the doctor doctor kind. So I don’t usually report on medical stuff (with the exception of vaccines, of course) … but when I read this headline from a press release about a particular research paper, I knew right away I simply had to write about it:

“Researchers Find Certain Roller Coasters May Help Small Kidney Stones Pass”

I know, right? And the story itself is pretty wonderful.*

I’m not sure I can write it better than the press release did:”

The foundational study was designed to validate the effectiveness of a 3D printed model kidney used in the research, led by a Michigan State University College of Osteopathic Medicine professor of urology. Dr. David D. Wartinger, currently professor emeritus, initiated the study when a series of patients reported passing kidney stones after riding the Big Thunder Mountain Railroad roller coaster at Walt Disney World in Orlando. In one case, a patient said he passed one kidney stone after each of three consecutive rides on the roller coaster.

OK, first, and again, I’m not a doctor so I’m not really in a position to analyze the accuracy of the research (though see the note at the end of this article). But, let’s assume for the moment that it’s good; the paper makes the usual caveats about preliminary findings supporting the anecdotal evidence.

But that’s what I like straight away about this: A doctor listened to his patients, heard their stories, got curious, and decided to look into the situation. That right off the bat is something I like to hear.

But then it’s how he tested things that slays me. Wartinger and a colleague used 3-D printing to make a silicone model of one of the patient’s kidneys (based on tomographic scans). They then—and get this—filled it with urine and put actual kidney stones of various sizes into it, placing one each in the upper, middle, and lower passageways.

Right? But it gets better:

The researchers, who had permission from the park, kept the kidney model concealed in a backpack during 20 rides on the Big Thunder Mountain Railroad roller coaster at Walt Disney World in Orlando. Researchers then analyzed those 60 ride outcomes to determine how the variables of kidney stone volume, location in the kidney and model position in the front versus rear of the roller coaster impacted kidney stone passage.

It’s OK if you want to read that again. To wit: They got permission from the park, stuffed the kidney model into a backpack, and then, unbeknownst to any other park celebrants, rode with the kidney on a roller coaster.

I hope they bought it some cotton candy first.

I love the idea of medical researchers going on a roller coaster with a fake silicone kidney filled with urine and actual crystals, probably enjoying the ride and screaming at the fun parts, getting off, checking the model, rotating and squeezing the model to reposition the stones … and riding the coaster again.

And then doing it again 18 more times.

And yes, they got some results: 64 percent of the time a stone passed if they sat in the back of the coaster, and about 17 percent of the time one passed if they sat in the front. That result was independent of the size of the stone or where it was in the fake model silicone kidney.

Mind you, from the writeup, this sounds like real science. They observed something, hypothesized an explanation, tested it, and varied their tests to measure the results better. They then conclude their results support the observations, though they don’t say it’s proof. But all in all this doesn’t sound too bad, and if these results pan out, it could prove pretty useful to people who have small to moderate sized stones. At the very least, it does seem to indicate further testing would be useful, including using actual kidneys for the experiment (silicone is not a perfect representative of tissue, after all; and in fact the purpose of this research was to see how well the model behaved in the first place).

So I guess I really only have one question: When they got their results, did they exclaim, “Urea!”?

*NB: The research described was done by an osteopath and will appear in the Journal of the American Osteopathic Association. Osteopathy is a form of alternative medicine, and while some of it uses rigorous medical procedure, there is a lot of quackery involved in the field as well. A whole lot. In the U.S., where this research was done, there appears to be higher scientific standards for osteopathy, though some is still suspect. Caveat lector et emptor. I’ll note that the research described seems legit; the careful mention of preliminary results supporting the anecdotal evidence gives me some degree of relief that this is not too extraordinary a claim. If there’s a doctor or other expert out there who disagrees, please let me know. You can reach me at

UPDATE (Sep. 27, 2016 at 14:30 UTC): Well, nuts. In this post I noted that the research described may not hold water, and I am now hearing word that this may very well be the case. I will update again when I get more information. For now, please keep that in mind while reading.

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