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

To compare the outcome of two different targeting strategies for treating radiolucent ureteric calculi by extracorporeal shock wave lithotripsy (ESWL), focusing the shock waves either at the end or 5 mm beyond the column of contrast medium visible in the ureter.

A total of 156 patients undergoing ESWL for a radiolucent ureteric stone were randomized into two groups. Group 1 comprised 74 patients in whom the shock waves were focused on the end of the contrast medium column, and group 2 comprised 82 patients in whom the shock waves were focused 5 mm beyond the end of the column.

Both groups had comparable distributions of age, gender, treatment methods and stone characteristics. There were no adverse reactions to the contrast medium. The stone-free rate after 2 months was 17% greater in group 2 (91%) than in group 1 (74%; P < 0.05).

The administration of intravenous contrast medium for ESWL of radiolucent ureteric calculi is effective and safe. We recommend that the shock waves are focused 5 mm beyond the end of the column of contrast medium, except where a stone becomes clearly visible within the column.