A novel, ultra-low X-ray protocol can reduce fluoroscopy use and ionizing radiation exposure during ureteroscopy (URS) for 10 to 20 mm single kidney stones located within the renal collecting system, according to a new study published in Urology.

Two highly trained endourological surgeons at the University of Freiburg in Freiburg, Germany, followed a standardized, step-by-step retrograde intrarenal surgery (RIRS) technique designed to minimize radiation control while employing ultra-low fluoroscopy. Generally, fluoroscopy was not used to guide stent placement prior to RIRS. Surgeons used endoscopy instead of a retrograde ureter study, placing guidewires without radiologic control. They placed a ureteral access sheath without fluoroscopy. Accessible calyces precluded additional fluoroscopy. Finally, surgeons inserted a JJ stent without continuous X-ray exposure. The procedures were adapted to suit the patient and circumstances.

Radiation exposure fell over time, possibly due to the protocol and growing surgeon experience. Over the course of 174 specific procedures performed from 2009 to 2015, average fluoroscopy time dropped from 167.7 to 7.4 seconds and dose area product from 318.4 to 6.4 cGy/cm2. Stone-free rates improved from 66.7% to 100%. The investigators noted that pre-stenting was used in nearly a third of procedures and may have facilitated passage. Intraoperative complications graded Satava 1 and 2 dropped from 28.5% to 4.8% over the study period. Operations also took less time to perform (91 vs 65 minutes). Retreatment was required in just 2.9% of cases.

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The novel protocol is as effective as current methods, according to Simon Hein, MD, and fellow investigators at the University of Freiburg. “Exposure to ionizing radiation can be significantly reduced if the presented protocol is followed strictly,” they emphasized.

Ureteral stones and renal calculi larger and smaller than 10 to 20 mm were excluded from the study, so the results may not be generalizable. Additional prospective studies testing the protocol are warranted to confirm the findings.

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Hein S, Schoenthaler M, Wilhelm K, Schlager D, Vach W, Wetterauer U, Miernik A. Ultra-Low Radiation Exposure during Flexible Ureteroscopy in Nephrolithiasis Patients – How Far Can We Go? Urol. doi: 10.1016/j.urology.2017.06.016