A study was done by doctors on the effects of roller coaster rides and kidney stones after a patient claimed that the rides were an aid in passing his stones. According to an article published in The Journal of American Osteopathic Association, roller coaster rides may help patients pass stones 5 millimeters or less in diameter. The study was conducted on the Big Mountain Railroad roller coaster at Disney world. The sensations of a drop in the gut, pang in the back, kick to the lower abdomen, urgency in the bladder are common in both riding a coaster and in passing a stone. To test their theory, a 3-D model was constructed of a kidney with stones and doctors proceeded to see the effects of movement as they rode the coasters. There was definite movement from what would have been the outer ducts of the kidney to the ureter. Another reason to spend a day at an amusement park.