Ng CF et al, 2016: A prospective randomized study comparing the effect of different kidney protection treatment protocols on acute renal injury after extracorporeal shockwave lithotripsy.
Ng CF, Luke S, Yee CH, Chu W, Wong KT, Yuen J.
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong , Shatin, Hong Kong.
Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong , Shatin, Hong Kong.
Department of Health Technology and Informatics, Hong Kong Polytechnic University , Hong Kong.
Objectives: To perform a prospective study to evaluate the renal protective effects of ramping protocol and pause protocol for extracorporeal shockwave lithotripsy in human subjects.
Patients and Methods: 320 patients with solitary renal stone <15mm, were randomized to receive one of four protocols: (1) 80% power from beginning until the end of treatment; (2) the first 100 SWs at 40% power, and then 80% power until the end of treatment; (3) the first 100 shocks at 40% power, followed by a 3-minute pause and then further SWs at 80% power until the end of treatment; and (4) the first 100 shocks at 80% power, followed by a 3-minute pause and then further SWs at 80% power until the end of treatment. The primary end-point was the incidence of renal haematoma assessed by imaging on Day-2. Spot urine samples were also collected before and after treatment for acute renal injury marker measurement.
Results: The baseline information and treatment parameters of the four groups were comparable. The overall incidence of haematoma formation was 7.69% (24 patients). The number of patients developing haematoma in the four groups was 8 (10.26%), 7 (8.97%), 6 (7.59%) and 3 (3.90%), respectively, and the incidence of haematoma among the four groups was not significantly different. Only patient's body mass index and mean blood pressure during treatment were predictors for haematoma formation. There was also no significant difference in changes in the levels of all markers, complication and hospitalization rates between the four groups.
Conclusion: Comprehensive assessment of clinical parameters, imaging results and urinary markers showed no obvious improvement in post-SWL renal insult by either protocol.
J Endourol. 2016 Oct 20. [Epub ahead of print]
This is an interesting and well conducted report on development of renal hematoma and kidney injuries following SWL. The treatments were carried out with an electro-conductive lithotripter and a comparison was made between different renal protective protocols.
MRI was used to detect hematoma, a complication that in average was observed in roughly 8% of the patients. Of these patients symptomatic hematomas were recorded in only approximately 1% of the treated patients. The latter figure is in line with numerous other clinical reports. The bottom-line of this study was that there were no significant changes in formation of hematoma with the four tissue protective protocols:
A. Maximum level (80%) throughout the whole treatment
B. First 100 SW at low level (40%) and the remaining treatment at maximal level (80%)
C. First 100 SW at low level (40%), pause 3 min, and the remaining treatment at maximal level (80%)
D. First 100 SW at maximum level (80%), pause 3 min, and the remaining treatment at maximal level (80%)
The authors mention ramping as part of the procedure, but although they increased the power from 40 to 80% within 20 SW (B and C), this is not what usually is meant by ramping in which the energy is increased stepwise to the maximum level. Moreover, all treatments were carried out at a frequency of 2Hz.
The results presented in this report raise doubt on the clinical usefulness of starting the treatment at low energy and/or have a pause after that in order to obtain vasoconstriction and thereby avoid hemorrhagic complications. It is important to note, however, that the lithotripter used for these treatments had a small and sharp focal volume (3.2 x 2.7 x 21.1 mm at setting 73%). It is thus not possible to conclude that these observations are valid also for other lithotripters with different geometrical and physical properties.
One point that surprised me was that the authors expected an incidence of renal hematoma in as many as 35% of the patients. In view of this assumption there is no explanation provided why the incidence in their patients was not higher than 8%. There are only few MRI examinations after SWL reported in the literature, but with the HM3 device Kaude and co-workers  found hematoma in 24% of SWL-treated patients.
The bottom-line was that there were no significant differences that could be explained by the different treatment protocols. Markers of injuries to the renal tissue were normalised after 2 days except for NGAL that were highest in Group D in which the incidence of hematoma had the numerically lowest value.
It is definitely of interest to analyse the outcome of SWL in this regard also with other lithotripters.
1. Kaude JV, Williams CM, Millner MR, Scott KN, Finlayson B.
Renal morphology and function immediately after extracorporeal shock-wave lithotripsy.
AJR Am J Roentgenol. 1985 Aug;145(2):305-13.