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Kang DH et al, 2016: Ureteral stenting can be a negative predictor for successful outcome following shock wave lithotripsy in patients with ureteral stones.

Kang DH, Cho KS, Ham WS, Chung DY, Kwon JK, Choi YD, Lee JY.
Department of Urology, Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
Department of Urology, Gangnam Severance Hospital, Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.

Abstract

PURPOSE: To evaluate ureteral stenting as a negative predictive factor influencing ureteral stone clearance and to estimate the probability of one-session success in shock wave lithotripsy (SWL) patients with a ureteral stone.
MATERIALS AND METHODS: We retrospectively reviewed the medical records of 1,651 patients who underwent their first SWL. Among these patients, 680 had a ureteral stone measuring 4-20 mm and were thus eligible for our study. The 57 patients who underwent ureteral stenting during SWL were identified. Maximal stone length (MSL), mean stone density (MSD), skin-to-stone distance (SSD), and stone heterogeneity index (SHI) were determined by pre-SWL noncontrast computed tomography.
RESULTS: After propensity score matching, 399 patients were extracted from the total patient cohort. There were no significant differences between stenting and stentless groups after matching, except for a higher one-session success rate in the stentless group (78.6% vs. 49.1%, p=0.026). In multivariate analysis, shorter MSL, lower MSD, higher SHI, and absence of a stent were positive predictors for one-session success in patients who underwent SWL. Using cutoff values of MSL and MSD obtained from receiver operator curve analysis, in patients with a lower MSD (≤784 HU), the success rate was lower in those with a stent (61.1%) than in those without (83.5%) (p=0.001). However, in patients with a higher MSL (>10 mm), the success rate was lower in those with a stent (23.6%) than in those without (52.2%) (p=0.002).
CONCLUSIONS: Ureteral stenting during SWL was a negative predictor of one-session success in patients with a ureteral stone.

Investig Clin Urol. 2016 Nov;57(6):408-416.

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Comments 1

Hans-Göran Tiselius on Wednesday, 26 April 2017 10:43

The negative influence of stents when treating patients with ureteral stones is confirmed in this report. It needs to be noted that this report only has its focus on stones in the ureter. The negative effect of a stents might be related to the oedema and impaction of the stone by the pressure from the stent. That the stent will shield the stone and take up energy is in my mind less likely or at least difficult to prove inasmuch as the stent will take many different positions relative to the stone and the shockwave path.

My own experience is that stents or ureteral catheters [1] are of limited value for SWL of ureteral stones and when stents are present they might better be removed before the SWL session. In case of subsequent obstruction it is almost always possible to insert or re-insert a stent, but this is only occasionally necessary.

For large stones in the kidney the situation is different and it needs to be emphasized that whereas accumulation of gravel in the ureter cannot be counteracted by the stent, the obstruction can. Different definitions of steinstrasse are found in the literature and my personal definition is that this complication comprises combined accumulation fragments in a column and obstruction to the urine flow.

Reference
1. Tiselius HG. Anesthesia-free extracorporeal shock wave lithotripsy of distal ureteral stones without a ureteral catheter.J Endourol. 1993 Aug;7(4):285-287

The negative influence of stents when treating patients with ureteral stones is confirmed in this report. It needs to be noted that this report only has its focus on stones in the ureter. The negative effect of a stents might be related to the oedema and impaction of the stone by the pressure from the stent. That the stent will shield the stone and take up energy is in my mind less likely or at least difficult to prove inasmuch as the stent will take many different positions relative to the stone and the shockwave path. My own experience is that stents or ureteral catheters [1] are of limited value for SWL of ureteral stones and when stents are present they might better be removed before the SWL session. In case of subsequent obstruction it is almost always possible to insert or re-insert a stent, but this is only occasionally necessary. For large stones in the kidney the situation is different and it needs to be emphasized that whereas accumulation of gravel in the ureter cannot be counteracted by the stent, the obstruction can. Different definitions of steinstrasse are found in the literature and my personal definition is that this complication comprises combined accumulation fragments in a column and obstruction to the urine flow. Reference 1. Tiselius HG. Anesthesia-free extracorporeal shock wave lithotripsy of distal ureteral stones without a ureteral catheter.J Endourol. 1993 Aug;7(4):285-287
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