WEDNESDAY, April 12, 2006 (HealthDay News) -- Doctors are reacting cautiously to a report linking a popular shock wave therapy that breaks up kidney stones to an increased risk of diabetes and hypertension.
Mayo Clinic researchers report in the April issue of the Journal of Urology that patients who undergo the procedure, called lithotripsy, are nearly four times more likely to develop diabetes and face a nearly 50 percent higher risk of high blood pressure over the following decades than those getting alternative treatment.
However, that has not changed the use of lithotripsy at the Mayo Clinic, said study author Dr. Amy Krambeck, a urology resident.
"We continue to use lithotripsy," Krambeck said. She said it has a "definite role" in helping patients get rid of the painful stones.
The study is far from definitive, Krambeck pointed out. "If we could say for certain we found an exact cause, it would be different."
Dr. Philip Mosca, an Oklahoma City physician who is also president of the Urology Society of America, echoed those sentiments. He noted that the Mayo Clinic study was "retrospective," meaning that it looked at historical results rather than being a prospective, controlled trial. "Retrospective studies are always suspect," he said.
According to the U.S. National Institutes of Health, 10 percent of men and 5 percent of women can expect to develop a kidney stone before the age of 70, and Mayo Clinic experts say that about 1 million Americans have undergone lithotripsy so far.
In the study, the first to look at long-term effects of lithotripsy, the Mayo team sent questionnaires to 630 people who got the shock wave treatment at the clinic in 1985. Their outcomes were compared to a matched set of patients who received an alternate therapy to deal with their kidney stones.
The researchers found an increased incidence of diabetes and high blood pressure in the 60 percent of lithotripsy patients who responded to the questionnaire.
But Mosca said lithotripsy has changed a lot since 1985, so the results may not be relevant for individuals undergoing the procedure today. "At that time, people were probably overtreating a bit," he said. "Also, they used the HM3 machine, which produces the highest energy of any lithotripsy machine."
Another reason for caution was the use of questionnaires, Mosca said. "If you interview people [face to face] you get different results," he said.
And there's another reason to doubt the findings, a least as they pertain to diabetes: insulin is produced in the pancreas, which is unaffected by lithotripsy. "Usually the path of the beam is not through the pancreas," Mosca said.
True, said Krambeck, but that assumes perfect aim on the part of the practitioner. "The pancreas could be hit by shock waves if not correctly focused," she said.
Mosca said he has no plans to reduce or stop using lithotripsy. "At this moment, no," he said. "Not until I saw something that was prospective and a little less uncontrolled."
Prospective studies, aimed at following patients carefully after treatment, are in the planning stages, Krambeck said.
Meanwhile, little has changed at the Mayo Clinic, she said. Urologists there are still using the HM3 machine, which Krambeck called "the gold standard."
"Most of our patients have been receptive to shock wave therapy," she said, even after being told about the potential long-term risks. Many prefer it to alternative treatments such as surgery, Krambeck added.
For more on kidney stones and their treatment, head to the Mayo Clinic.