ORLANDO—Even multiple shock wave lithotripsy (SWL) treatments have negligible impact on global renal function, Canadian researchers reported at the American Urological Association 2014 annual meeting.

Stephanie Tam, MD, and collaborators at the University of Toronto retrospectively analyzed data from 324 patients who underwent at least 1 SWL treatment and 2 or more 24-hour urine collections at Toronto’s St. Michael’s Hospital from 2002-2013.

The investigators divided patients into 3 groups based on the number of SWL treatments. 1, 2-5, and more than 5. As a marker of renal function, they used estimated glomerular filtration rate (eGFR) as calculated using the Modification of Diet in Renal Disease study equation.

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Of the 324 patients, 90% had normal renal function or mild chronic kidney disease (CKD) at baseline. Forty-four had 1 SWL treatment, 227 had 2-5 treatments, and 44 had more than 5 treatments. The researchers found no significant difference in baseline renal function in patients requiring more treatments (82.7 vs. 84.9 vs. 81.8 mL/min/1.73 m2).

In multivariate analysis, age was the only predictor of final eGFR. Additionally, results showed no difference in change in eGFR among patients treated with a single SWL treatment compared with those who had multiple treatments. While CKD class deteriorated in 8.7% of patients, it improved in 4.3%, and the number of SWL treatments did not impact change in CKD class.

“There has been a growing body of evidence that stone formers are at a higher risk of developing kidney disease in the long run, and there have been some animal studies to suggest that shock wave lithotripsy may result in renal fibrosis, which could obviously impact renal function down the road,” said Dr. Tam, a urology fellow.

“Overall, there was a slight decrease in renal function after shock wave [lithotripsy], but when we looked at it based on the number of treatments the patients received, there was no correlation between shock waves and deterioration of renal function.”