Piezoelectric extracorporeal shockwave lithotripsy of distal ureteric calculi: assessment of shockwave focusing with unenhanced spiral computed tomography

Objective To assess the effects of the interposition of pelvic bones and abdominal gas in the shockwave pathway during piezoelectric extracorporeal shock wave lithotripsy (ESWL) of distal ureteric stones. Patients and methods The study included 35 patients who were evaluated with unenhanced spiral computed tomography (CT), used according to their positioning during ESWL. The shockwave pathway was simulated on the sagittal and coronal views crossing the ureteric calculi, allowing a theoretical evaluation of the effective shockwave focusing (with no bone or gas interference). Vertical and oblique approaches were statistically compared for bone and gas interposition. Results Overall, the effective shockwave focusing during in situ piezoelectric ESWL of distal ureteric stones was 71% of the theoretical area. The interposition of bone and gas was significantly lower for an oblique access than for a vertical approach in the sagittal plane (P