Could riding roller coasters help you pass kidney stones?

"Got kidney stones? Ride a roller coaster! Study shows it is the most pain-free cost-efficient way to pass them," says the Mail Online of a study carried out in the US which tested riding roller coasters as a way of passing kidney stones.

The study came about after a number of people with kidney stones claimed riding on Walt Disney World's Big Thunder Mountain Railroad ride had helped them pass their stones. In particular, one person with kidney stones reported passing a stone after each of three consecutive rides. This prompted a research team from Michigan State University, led by Dr David Wartinger, to investigate further.

The researchers rode the Big Thunder Mountain Railroad ride a total of 60 times carrying a 3D printed model kidney made from silicone. The kidney contained urine and kidney stones of three different sizes.

They found that the rides caused the kidney stones to be passed from the kidney, and that the position on the ride made a big difference to the number of stones passed. Sitting at the back of the ride produced the best results.

A key limitation of the study is that the research was carried out on a model kidney rather than on the kidneys of real people. This method can never truly replicate the behaviour of the stones in a real kidney. However, the findings may support the case for further research into what it is about the ride that might cause stones to pass.

Where did the story come from?

The study was carried out by researchers from Michigan State University, who reported no source of funding for the study. 

The report was published in the peer-reviewed Journal of the American Osteopathic Association.

The Mail Online and The Telegraph presented the main findings of the study but fail to mention any of the limitations of the research.

What kind of research was this?

This was an experimental study which aimed to assess roller coaster rides as a method of passing kidney stones.

Kidney stones are formed when certain chemicals, usually calcium, or uric acid, build up in the body. Some medical conditions can contribute to high levels of these substances being in the body. They are more likely if you don't drink enough fluids.

This study is able to provide possible links for further investigation but can't provide any conclusive evidence that would be applicable to all. The study team appreciate this limitation and were reported in the Mail Online as saying: "The purpose of this initial study was to validate the effectiveness of the model and support the case for further research."

What did the research involve?

The researchers aimed to assess the effectiveness of roller coaster rides for passing kidney stones by creating an anatomical model of the kidney and taking this on a number of rides to test various scenarios of stone position within the kidney and different seating positions on the ride.

The roller coaster, Walt Disney World's Big Thunder Mountain Railroad ride, had a maximum speed of 35mph, took sharp turns and had quick drops. The ride did not go upside down and lasted for two and a half minutes.

The model itself was made of clear silicone to allow direct inspection of the stone location after each ride and was based on the kidney scan of the patient providing the kidney stones for the test.

The stones were suspended in urine within the model and were of three different volumes:

• 4.5 mm3
• 13.5 mm3
• 64.6 mm3

The model was placed in a padded backpack that was positioned at kidney height at the back of the seat on the roller coaster, between the researchers. Data was gathered 20 times for each of the kidney chambers, eight rides in the front seating and 12 in the rear seating. 

What were the basic results?

Sixty roller coaster rides were taken and the effect on the kidney stones analysed.

When the model was carried in the front seating of the roller coaster fewer kidney stones were passed (16.7%) than when sat in the rear seating (63.9%).

The position of the stone also appears to make a difference to the rate of passage. If the stone is in the upper chambers (calyces) of the kidney it is passed more frequently than when it is in the middle or lower chambers. In fact, when the model was carried in the rear of the roller coaster, stones in the upper chamber were passed 100% of the time. 

The size of the stone did not appear to influence the proportion of stones passed.

How did the researchers interpret the results?

The researchers concluded that their model served as a functional patient surrogate to evaluate activities that facilitate the passing of kidney stones. In other words, they could expect the kidneys and kidney stones of real people to behave in the same way as the model. They state that the rear seating position on the roller coaster led to the most kidney stones being passed.

Conclusion

This experimental study assessed going on roller coasters as a means of passing kidney stones.

Prior to this study there had been a number of reports that riding on roller coasters had caused people to pass their kidney stones, with one person claiming to have passed three kidney stones after three consecutive rides on the Big Thunder Mountain Railroad roller coaster at Disney World in Florida.

The researchers found a similar effect using their model, and also saw that the seating position on the ride made a big difference, with almost four times the number of stones passing in the rear of the ride compared to the front.

There are a number of limitations to this research:

• The study used an anatomical model of the kidney rather than actual people. This will never truly replicate the behaviour of the stones in a real kidney.
• The model was based on a single person with kidney stones. The anatomy of this person's kidney will not be the same as other peoples' because the anatomy of an individual's kidneys is unique, much like a fingerprint.
• Only a single roller coaster was used. The same effect may not be seen on other rides with different characteristics.

However, as the research team told the media, this was an initial study to validate the effectiveness of the model and support the case for further research.

Some symptoms of kidney stones to be aware of are:

• a persistent ache in the lower back
• periods of intense pain in the back or side of your abdomen
• feeling sick
• needing to urinate more often than normal
• pain when you urinate
• blood in your urine 

To prevent kidney stones make sure you avoid becoming dehydrated. Drinks such as tea, coffee and fruit juice can count towards your fluid intake, but water is the healthiest option and is best for preventing kidney stones developing. Make sure you drink more when it is hot or when you are exercising, to replenish fluids lost through sweating.