Extracorporeal shock wave lithotripsy for distal ureteral calculi: Improved efficacy using low frequency

Abstract

To compare low versus high frequency for lithotripsy in the management of distal ureteral calculi. A total of 154 patients with radio-opaque calculi (0.5-1 cm diameter) in the distal ureter were randomized to be given either lithotripsy at 80 or 60 pulses per min (high frequency or low frequency groups, respectively). The number of waves and sessions received, and time to total resolution were measured. A Dornier Compact Delta lithotripter was used. A total of 72 patients were assigned to the high frequency group and 78 to the low frequency group. Four patients were excluded from the study because of intolerance of the procedure. The size was slightly lower in low frequency group, whereby an analysis of covariance was carried out to eliminate the size factor, with the limit established as 0.7 cm. The low frequency group received 2980 ± 1211 waves, and the high frequency group received 5752 ± 3121 (P<0.001). The success rate was higher in the low frequency group (100%) than in the high frequency group (92.9%; P=0.02). If adjusted to the size of the calculus with a threshold of 0.7 cm, there was a difference, although it was not statistically significant. The time to elimination of the fragments was higher in the high frequency group (17.68 days) than in the low frequency group (7.15 days; P<0.001). The number of sessions necessary for resolution was higher in the high frequency group (1.56) than in the low frequency group (1.14; P<0.001). Lithotripsy at 60 pulses provides better outcomes than lithotripsy at 80 pulses for the treatment of distal ureteral calculi.