Mohammadi A. et al., 2023: Does the Prone Position During the Shockwave Lithotripsy of Kidney Stones Improve the Stone-Free Rate? Results from a Randomized Clinical Trial
Mohammadi A, Oliveira Reis L, Khajavi A, Zareian Baghdadabad L, Aghamir SMK.
Urology Research Center, Tehran University of Medical Sciences, Tehran, Iran.
UroScience and Department of Surgery (Urology), School of Medical Sciences, University of Campinas, Unicamp and Pontifical Catholic University of Campinas, PUC-Campinas, Campinas, São Paulo, Brazil.
School of Allied Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Urology Research Center, Tehran University of Medical Sciences, Tehran, Iran.
Urology Research Center, Tehran University of Medical Sciences, Tehran, Iran.
Abstract
Objective: This study aimed to evaluate the impact of the skin-to-stone distance in the supine and prone positions on the outcome of shockwave lithotripsy of kidney stones.
Methods: In a prospective randomized clinical trial study, 81 patients that candidates for shockwave lithotripsy (SWL) of kidney stones were randomly divided into two groups to perform SWL in the prone position (40 patients) or conventional supine position (41 patients). Demographic data, stone characteristics, skin-to-stone distances (SSD) in CT, SSD during SWL with an ultrasound probe in prone and supine positions, total shock wave rate, total energy (kilovolt), visual analog scale (VAS), complications (Clavien-Dindo scale system), and SWL success rate evaluated in two intervention and control groups. All statistical analysis was performed by independent T-test, Chi-Square test, Fisher exact test, paired T-test, and SPSS 22.0 software for windows. Results: There were no significant differences between demographic characteristics, SWL sessions, the median number of SWLs, the median SWL time, median total energy, VAS, and complications in the two groups. The SFR was numerically higher in the prone SWL group than in the supine SWL group (80% vs. 73.2%) but was not significantly different (p-value: 0.468). Also, the inline ultrasound (US) measuring of the SSD in the prone position was significantly different from US SSD measures in the supine position in the two groups (p-values=0.001 and 0.024). The mean SSD was lower in the US measurement during the SWL process that measured in supine and prone position than the CT measurement (73.5 vs. 101.1), which means the routine SSD measured by CT scan is higher than SSD in the US probe measurement during SWL.
Conclusion: The prone position SWL modification could be effective in obese patients with a BMI of more than 30 and increase the stone-free rate (p-value=0.039) with a similar safety profile and comparable VAS score. It seems the SSD measured by the ultrasound is a more accurate dynamic measurement during the SWL and needs to define the SSD according to the SSD calculation by the US probe of the therapy head. SFR was numerically higher in the prone compared with the supine treatment groups.
Urol J. 2023 Jan 25. doi: 10.22037/uj.v20i.7418. Online ahead of print. PMID: 36695211. FREE ARTICLE
Comments 1
It is repeatedly discussed in the literature whether prone or supine positioning during SWL should be chosen for superior result. Formulated differently the question is whether shock waves administered from the back or transabdominally are best? There is, however, no easy answer to that question because patient positioning is one factor that needs to be individually chosen given the treatment situation as well as the stone appearance and location.
In the current report the authors focused on how positioning affected the SSD. The conclusion was that the prone position was advantageous in obese patients in whom a BMI of 30 was suggested as a practical limit. Moreover, it is of note that SSD decreased significantly when patients were placed in prone position. The other observation reported in this study is that SSD most accurately is measured with US!
Of factors that are influenced by patient positioning, in my opinion, SSD is the least important, because any excessive SSD usually can be dealt with by applying “blast-path” technique. There are, however, other more important determinants of SWL success such as to avoid interference between the shock wave path and skeletal structures when administering shock waves from the back and interference with intestinal gas when shock waves are administered transabdominally.
The bottom-line is that optimal SWL requires analysis of several important factors and accordingly placing the patient in a way that allows the best hit of the stones by shock waves.
It thus is obvious that randomization of patients to prone or supine position only accounts for ONE factor. Interestingly, all patients in this study were given antibiotics whereas analgesics were not routinely administered!
Hans-Göran Tiselius