The Influence of Stone Size, Skin to Stone Distance and Hydronephrosis on Extracorporeal Shock Wave Lithotripsy Session and Shock Wave Numbers in Ureteral Stones

Abstract

Background: To evaluate the impact of stone size, grade of hydronephrosis induced by the stone and skin to stone distance (SSD) on the shock wave lithotripsy (SWL) outcome in terms of SWL session and shock wave (SW) numbers in patients with ureteral stones.

Methods: Between June 2011 and December 2011, data of 80 patients undergoing SWL for ureteral stones were retrospectively reviewed. Patients were classified into three groups according to hydronephrotic grades (group 1, grade 1 hydronephrosis; group 2, grade 2 hydronephrosis; group 3, grade 3 hydronephrosis) and into two groups according to stone size (group 1, stone size = or < 10 mm and group 2, stone size > 10 mm). The effect of hydronephrotic grade, SSD and stone size on SWL sessions and SW rates were studied. The impact of the stone size on hydronephrosis was also analyzed.

Result: Of the 80 patients undergoing SWL, 24 were female and 56 were male. The mean age, stone size, number of sessions, SW rate and SSD were 37.7 (16 - 73), 9.6 mm (6 - 19), 1.65 (1 - 4), 3,812 (1,200 - 8,500) and 9.6 cm (5 - 15) respectively. Thirty-five patients had grade 1, 29 grade 2 and 16 grade 3 hydronephrosis. Twenty-eight patients had upper, 19 mid and 33 lower ureteral stones. There were significant correlation between stone size and SW number (r = 0.513, P < 0.001), and between stone size and session number (r = 0.609, P < 0.001). The correlation between hydronephrotic grade, SW and session numbers was also significant (r = 0.472, P < 0.001 and r = 0.441, P < 0.001). There was no correlation between SSD and SW and session numbers. Four patients with stone size more than 10 mm and grade 2-3 hydronephrosis had unsuccessful SWL outcome.

Conclusion: The grade of hydronephrosis and stone size are independent predictive factors for SW and SWL session numbers and indirectly for treatment outcome. SSD was not found to be predictive.

World J Nephrol Urol. 2013;2(2):60-64
doi: http://dx.doi.org/10.4021/wjnu127w