MONTREAL—New findings challenge the need for universal antibiotic prophylaxis prior to shock wave lithotripsy (SWL), investigators reported at the Canadian Urological Association annual meeting.

The findings come from a study of 526 patients undergoing SWL for renal and ureteral stones at St. Michael’s Hospital of the University of Toronto, which has a policy of targeted antibiotic prophylaxis prior to SWL.

Joshua D. Wiesenthal, MD, and colleagues at St. Michael’s, noted that the American Urological Association’s Best Practice Policy Statement on Urological Surgery Antimicrobial Prophylaxis uses level 1A evidence to indicate universal antibiotic prophylaxis and the European Association of Urology’s Guidelines on Urological Infections uses level 1A evidence to indicate prophylaxis only in patients with urinary drainage tubes, ureteral stents, or infected stones.

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In the St. Michael’s study, all patients underwent urine dipstick analysis, microscopy, and culture prior to treatment. Antibiotic prophylaxis was administered only to patients with nephrostomy tubes, a history of infected stones, or urine dipstick findings showing nitrites and leukocytes. The presence of ureteral stents was not an indication for prophylaxis. All patients had a urine culture performed three days prior to SWL if they did not undergo antibiotic prophylaxis or two days after finishing their course of antibiotic prophylaxis.

Of the 526 patients, 78 (15.1%) underwent SWL with previously placed ureteral stents. Ten patients (2.2%) were given antibiotic prophylaxis (six of whom had ureteral stents) and 14 (2.7%) were given antibiotics post-treatment. Post-SWL, a urinary tract infection developed in only one patient (0.2%) and asymptomatic bacteriuria developed in four (0.8%).

“This study contradicts the premise behind the AUA’s Best Practice Policy Statement by demonstrating an extremely low incidence of de novo urinary tract infections in patients treated without universal antibiotic prophylaxis prior to SWL,” Dr. Wiesenthal told Renal & Urology News. “By eliminating the need for universal antibiotic prophylaxis at the time of SWL, there is a huge potential cost savings to both the patient and health care system.”

He added: “Hopefully this study will add to the body of literature on this topic, and might serve to change the recommendations from the AUA such that they align more with the European’s guideline recommendation of targeted prophylaxis only.”

The new findings generally are in line with those of a study led by Mordechai Duvdevani, MD, Director of Endourology and Lithotripsy at Hadassah Ein-Kerem University Hospital, The Hebrew University, Jerusalem, Israel. The study, which looked at 11,500 SWL treatments, found that only 1.4% of patients had fever following treatment. “Therefore, we concluded that it is irrational to treat every patient who is undergoing SWL with prophylactic antibiotics,” he said. “We suggested that treating these patients selectively can decrease the amount of antibiotics use in these procedures and decrease the risk for development of fever after SWL.”

In addition, he noted that the study by Dr. Wiesenthal and colleagues suggests that urine dipstick tests for both nitrites and leukocytes are not good predictors for concurrent UTI, he noted.