Stone area and volume are correlated with operative time for cystolithotripsy for bladder calculi using a holmium: yttrium garnet laser.

Abstract

Objective: This study investigated the correlation between the operation time and the stone size as determined by multiple modalities and the computed tomography (CT) densities of bladder calculi using holmium: yttrium garnet (Ho:YAG) laser lithotripsy.

Material and methods: A total of 68 patients underwent cystolithotripsy from March 2010 to October 2011. Thirty-six of these patients underwent cystolithotripsy using a Ho:YAG laser for bladder calculi by a single surgeon. The stone size was assessed by six modalities: sum of the stones' diameters: stone burden; maximum stone's diameter; number of stones; sum of the area using axial CT; sum of area using kidney-ureter-bladder (KUB) films; and volume using CT. In addition, the stone's CT density was measured by: the mean CT density of the maximum stone's whole area; maximum CT density of the maximum stone's whole area; and mean CT density of the maximum stone's center area. Correlations between the operation time and the stone size and the stone CT density were assessed.

Results: A total of 36 patients (30 male and six female) who underwent cystolithotripsy using a Ho:YAG laser for bladder calculi were enrolled in this study. Spearman correlation showed that the area and volume were strongly correlated with the operative time. The multipliers between the stone size and stone CT density showed no advantages based on the stone area or volume alone.

Conclusion: The area and volume of the stones correlated more closely with the operation time than the stone burden for bladder calculi lithotripsy using a Ho:YAG laser.