The radiolucent ureteric calculus at the end of a contrast-medium column: where to focus the shock waves

Objective To compare the outcome of two different targeting strategies for treating radiolucent ureteric calculi by extracorporeal shock wave lithotri psy (ESWL), focusing the shock waves either at the end or 5 mm beyond the c olumn of contrast medium visible in the ureter. Patients and methods A total of 156 patients undergoing ESWL for a radioluc ent ureteric stone were randomized into two groups. Group 1 comprised 74 pa tients in whom the shock waves were focused on the end of the contrast medi um column, and group 2 comprised 82 patients in whom the shock waves were f ocused 5 min beyond the end of the column. Results Both groups had comparable distributions of age, gender, treatment methods and stone characteristics. There were no adverse reactions to the c ontrast medium. The stone-free rate after 2 months was 17% greater in group 2 (91%) than in group 1 (74%; P < 0.05). Conclusions The administration of intravenous contrast medium for ESWL of r adiolucent ureteric calculi is effective and safe. We recommend that the sh ock waves are focused 5 mm beyond the end of the column of contrast medium, except where a stone becomes clearly visible within the column.