Objective: To determine whether roller coaster riding facilitates kidney stone passage using a pyelocalyceal model.

Design: Prospective model study.

Methods: Renal calculi of 4.5, 13.5, and 64.6 mm³ were suspended in urine in the model and taken for 20 rides on the Big Thunder Mountain Railroad roller coaster at Walt Disney World’s Magic Kingdom theme park in Orlando, Florida. The effects of the rides were analyzed according to stone size, calyceal location, position on roller coaster, and renal calculi passage.

Results: 60 renal calculi rides were examined. Front seating in the roller coaster resulted in 4 of 24 stone passages (16.7%), whereas rear seating on the roller coaster resulted in 23 of 36 passages (63.9%). For rear-seated passengers, upper, middle, and lower calyceal locations had 100.0%, 55.6%, and 40.0% passage rates, respectively.

Conclusions: The pyelocalyceal renal model was used to demonstrate that roller coaster riding may be an activity to facilitate stone passage. Rear seating on the roller coaster led to the most renal calculi passages.

Reviewer’s Comments: This article received a lot of lay press when it was published. It showed that the rigors of riding a roller coaster may facilitate stone passage.

Even though it led to a lot of discussion, the study itself is essentially a joke.

The model used is a simple silicone model of a kidney with stone passage defined as a stone getting to the ureteropelvic junction area of the model. It does not simulate real-life kidney stones in that in vivo kidney stones may be attached to papilla, have peristaltic forces of the renal pelvis and ureter, and the kidney itself does not shift as much in the human body as a plastic model in a backpack. The authors go on to even suggest that individuals who may be at risk for developing kidney stones ride a roller coaster to pass small flakes, which would not be as painful. I don’t think telling our patients to ride roller coasters is sound medical advice. All this model shows us is that roller coasters cause things to move or bounce around if unsuspended – I do not think it takes a study to prove that to us.(Reviewer–David A. Duchene, MD).