Evaluation of disintegration in prevesical ureteral calculi by 3-dimensional endo-ultrasound with surface rendering

Lower ureteral calculi are accessible by transrectal endo-ultrasound, including 3-dimensional image processing with surface rendering. We analyzed the efficiency of this innovative technology compared with that of standard radiographic examinations with respect to the outcome of extracorporeal shock wave lithotripsy (ESWL) (Dornier Medical Systems, Marietta, Georgia).

In patients with prevesical or intramural calculi we performed excretory urography and transrectal endo-ultrasound using a Combison 530 device (Kretz Technik, Zipf, Austria) with integrated optional 3-dimensional image processing and surface rendering. A total of 102 ESWL cases (108 radiopaque stones, 145 ESWL sessions) were included in the study. One day after ESWL an evaluation was independently performed by a radiologist (plain x-ray) and a urologist (transrectal endo-ultrasound). Results were compared to the outcome determined during further followup.

All stones were evaluable by endo-ultrasound with surface rendering, whereas in 27 cases the stone was hidden by extraureteral processes on followup radiography. Immediately after endo-ultrasound 8 calculi were passed. In 7 of the remaining 110 cases (6.4%) radiographic examination did not confirm sonographic findings. In these cases evaluation by surface rendering proved to be correct on followup.

Endo-ultrasound with surface rendering proved to be highly effective for evaluating ESWL success in cases of prevesical ureteral stones. This technique is independent from bowel gas or other factors that impede radiological imaging. It is safe, easy to learn, well tolerated by patients and does not expose them to radiation.