Use of the Echo Locator for In Situ Treatment of Ureteral Calculi with an Ultrasound-Based Lithotripter

Abstract

An experimental catheter (Echo Locator™) has been developed to facilitate ultrasonic localization of ureteral calculi. The Echo Locator consists of a small spherical piezoelectric crystal mounted on the tip of a 6F or 9F catheter, which is placed adjacent to the stone under fluoroscopic guidance. When activated by a frequencymatched ultrasound imaging probe, the Echo Locator generates a signal that is seen on the B-scan image and can be used to assist targeting of the shock wave focus for in situ lithotripsy. We used the Echo Locator successfully in five patients with ureteral stones that measured 6 to 20 mm. Four of the five patients were stone free at 30 days after a single lithotripsy treatment. Only one patient required a post-treatment ureteral stent. The Echo Locator is a valuable adjunct to renal lithotripters that incorporate ultrasound imaging, as it permits successful treatment of ureteral calculi without the potential sequelae of stone manipulation.