Radiographic prognostic criteria for extracorporeal shock-wave lithotripsy: a study of 485 patients

We studied 485 patients treated by extracorporeal shock-wave lithotripsy (ESWL) using an ultrasound electrohydraulic apparatus in an effort to define radiographic criteria for better patient selection for ESWL.

Results were assessed according to plain x-ray nephrotomography and ultrasound. The criteria for measuring success (stone free [SF]) excluded all residual fragments. After per-criteria analysis of the results, a multivariate analysis as well as an analysis of stone composition by infrared spectroscopy were performed.

The SF rate was 57.5% (279 of 485). Calculi that were smooth, denser than bone, located in the lower calyx, and larger than 15 mm had less satisfactory results despite a greater number of impulses. A correlation was established between the radiographic appearance of the calculus, its composition, and ESWL results. Rough, less dense calcium oxalate dihydrate yielded satisfactory results (65%), whereas smooth, dense calcium oxalate monohydrate led to less conclusive results (41%). Multivariate analysis demonstrated the predominant influence of radiographic calculus profile on the results: rough, less dense calculi yielded a 79.4% SF rate, whereas smooth, dense calculi yielded a 33.6% SF rate.

We propose that patients with dense, smooth calculi located in the lower calyx and larger than 15 mm be treated by other techniques, such as percutaneous nephrolithotomy. This would not only increase the ESWL effectiveness rate, but would also reduce the cost of treating kidney stones.