Chi-Fai N. et al., 2019: Effect of stepwise voltage escalation on treatment outcomes following extracorporeal shockwave lithotripsy of renal calculi: a prospective randomized study
Chi-Fai N, Yee CH, Teoh JY, Lau B, Leung SC, Wong CY, Tak WK, Chu WC, Yuen J.
SH Ho Urology Center, Department of Surgery, The Chinese University of Hong Kong , Hong Kong.
Department of Imaging and Intervention Radiology, The Chinese University of Hong Kong , Hong Kong.
School of Nursing, Hong Kong Polytechnic University , Hong Kong.
OBJECTIVE: This study aimed to assess the effects of a ramping protocol in patients receiving extracorporeal shockwave lithotripsy (SWL) for renal stones. METHODOLOGY: In this prospective study, patients with renal stones were randomized to receive SWL delivered using a ramping (First 1000 shocks at energy level-5, followed by 1000shocks at energy level-6 and 1000 final shocks at energy level-7; Group-1) or fixed-voltage (All 3000 shocks at energy level-7; Group-2) protocols by Modulith SLX-F2. The primary outcome was treatment success at 12weeks after a single SWL session, defined as the lack of a stone or a stone fragment <4 mm on computed tomography. Other outcomes included stone-free rate and the incidence of perinephric hematoma. RESULTS: 300 patients (150 per group) were recruited between February 2016 and June 2018. The two groups did not differ in terms of baseline parameters. Group-1 received significantly lower energy delivered than Group-2 (14.8% less, p<0.001). The treatment success rates for Group-1 and Group-2 were 67.8% and 73.6%, respectively, and were not statistically different (crude odds ratio for Group-1: 0.753; 95% confidence interval 0.456 to 1.244; p=0.268). The stone-free rates for Group-1 and Group-2 were 36.6% and 41.9%, respectively, and did not differ between the groups. However, in Group-1 and Group-2, 23.8% and 43.8% of patients developed perinephric hematoma, respectively, and was statistically significant difference (p<0.001). CONCLUSIONS: The fixed-voltage SWL and ramping protocols provided similar treatment success rates for renal stones. However, ramping protocol could reduce the incidence of post-SWL perinephric hematoma.
J Urol. 2019 May 21:101097JU0000000000000344. doi: 10.1097/JU.0000000000000344. [Epub ahead of print]
A very well designed and performed study that deserves reading! A few noteworthy details are:
“The thickness of haematoma for ramping and fixed-voltage were 15.0 mm and 24.8 mm, respectively.(p = 0.056) Group-1 and Group-2 had 4 and 0 symptomatic hematomas, respectively (p = 0.06)”
“Multivariate analysis was performed to assess the factors related to the treatment outcomes of SWL and the development of hematoma. Here, stone size was the only identified predictor of treatment success. Stone located in lower pole was the only factor affecting stone free rate. A larger stone size, higher dose of energy and the use of a fixed voltage protocol were found to predict a greater likelihood of hematoma formation after treatment.”
“Both groups exhibited statistically significant increases in the urinary levels of all markers
after SWL and returned to the baseline at 6 weeks after SWL.(Table-6) However, there were no significant interactions between time and treatment groups, and no inter-group differences were observed in any urinary marker level.”
“There were four patients with symptomatic hematoma, and all were in the ramping group. But the only symptom was pain, without hemodynamic disturbance recorded.”
Cross sectional imaging techniques are more precise and reliable than sonography to document post-EWSL hematomas. But surprisingly few and old clinical studies used these techniques (From reference 12 of the present paper) :
Baumgartner BR, Dickey KW, Ambrose SS, et al. Kidney changes after extracorporeal shock wave lithotripsy: appearance on MR imaging. Radiology 1987; 163: 531–4.
Rubin JI, Arger PH, Pollack HM, et al. Kidney changes after extracorporeal shock wave lithotripsy: CT evaluation. Radiology 1987; 162: 21–4.
Kaude JV, Williams CM, Millner MR, et al. Renal morphology and function immediately after extracorporeal shockwave lithotripsy. Am J Roentgenol 1985;145:305–13.
In the accepted unedited version of the manuscript available for reviewing it is not stated if the standard focal size (6mm x 28mm) was used for both groups. Total energy in the fixed voltage group was significantly higher than in the ramping group.