Multiple studies support safety of extracorporeal shock wave lithotripsy

Orlando, FL-Results from a series of studies presented at the 2008 AUA annual meeting fail to confirm prior evidence that extracorporeal shock wave lithotripsy (ESWL) treatment increases the risks of diabetes mellitus and hypertension.

These safety issues were examined by four groups of investigators in studies with different methods and durations of follow-up. Three of the four studies found no evidence of an association between new onset of diabetes and prior treatment with ESWL. In the fourth study, the prevalence of diabetes was higher among patients treated with ESWL 20 years earlier compared with the population average, although a multivariate analysis was not performed to control for other diabetes risk factors that differed in the patients and controls. Two studies examined the risk of hypertension and found no significant association with ESWL.

Researchers at the University of Tennessee undertook a retrospective case-control study using data from patients treated at the Memphis Veterans Administration Medical Center to investigate risks of both diabetes and hypertension. They compared patients treated for stone disease between 2002 and 2007 using ESWL (712 patients; median follow-up, 54 months) and those undergoing ureteroscopy ([URS] 146 patients; median follow-up, 47 months).

"Based on our study, we believe ESWL is a safe option for the treatment of urinary stone disease compared to ureteroscopy," Dr. Kincade said.

Researchers at the University of California, San Francisco also investigated risks of diabetes and hypertension associated with ESWL using a contemporaneous control group of stone patients consisting of those treated by URS or percutaneous nephrostolithotomy (PNL). A total of 948 patients treated between 1985 and 1989 were contacted by mail, but data for the study were obtained from only 76 patients. There was no significant difference between the ESWL and URS/PNL groups in the incidence of either diabetes (p=.57) or hypertension (p=.16). Side of treatment also did not correlate with development of diabetes or hypertension, nor did the number of shocks or intensity.

"Our poor response rate is a major limitation of our study," said first author Kirsten Greene, MD, assistant professor of urology, who conducted the study with Marshall Stoller, MD and colleagues. "Considering its limited power to detect a difference, if it exists, perhaps further investigation of an association between ESWL and hypertension is warranted. However, based on the p-value and absence of an effect of laterality of treatment on risk, the finding of a lack of association between ESWL and diabetes may be more real."

Population control studies

Two other studies examining diabetes risk after ESWL used population controls. Urologists at the University of Minnesota, Minneapolis conducted a mail survey of about 7,500 patients who had been treated for stone disease between 1999 and 2002. Of that group, 1,861 patients with complete data were included in the analysis. Median follow-up after ESWL was about 6 years.

The incidence of new-onset diabetes in the ESWL patients was compared with that in a control group derived from the National Health and Nutrition Examination Survey database matched by age, sex, and body mass index. The incidence of diabetes at baseline was similar in the ESWL patients and controls (8.7% vs. 8.3%), and was nearly identical in the two groups at study conclusion (13.9% vs. 14%). In a Kaplan-Meier analysis plotting absence of diabetes over time and including only ESWL patients and controls without diabetes at baseline, the curves for the two groups were nearly super-imposable.