Abstract
Background JJ stents are often encountered in patients with pelvic renal stones referred for shock wave lithotripsy, most of them being placed either for obstructive renal pelvic stones or for ureteric stones mobilized retrograde during the JJ stent insertion. The aim of the study was to determine whether the relative stone position in the upper loop of the JJ stent during extracorporeal shock wave lithotripsy (SWL) influences the efficiency of the procedure. The study was designed as a prospective cohort study on 162 patients addressing the same urological department, with single renal pelvic stone (primary or mobilized to the renal pelvis during the insertion of JJ stent), smaller than 15 mm, with JJ stent, treated by SWL using a second generation spark gap lithotripter, 18 kV, 3000 waves/session. Patients were divided in three groups according to the relative position of the stone to the upper loop of the JJ stent as appears on plain X-ray: stone-inside-loop, loop-crossing-stone and stone-outside the loop. The SWL success rate was the primary outcome of the study. p Value, Chi square and Kruskal–Wallis tests were used for statistical analysis.ResultsFor stone-inside-loop cases, SWL efficiency was 22.7 versus 42 % for all the other cases (p = 0.002). Other factors for decreased SWL success rate were: higher stone radio-opacity, larger JJ of stent and obese patients. Study limitation is represented by the relative small study group and by the evaluation of stone density using plain X-ray instead of computer tomography.ConclusionsFor pelvic renal stones having the same density characteristics studied by plain X-ray, the SWL efficiency is lower in stone-inside-loop cases comparing with the other positions. The overall stone free rate for renal pelvic stones could be explained by the second generation lithotripter used for all procedures.
Highlights
JJ stents are often encountered in patients with pelvic renal stones referred for shock wave lithotripsy, most of them being placed either for obstructive renal pelvic stones or for ureteric stones mobilized retrograde during the JJ stent insertion
Out of 162 patients, sixteen had the stent removed upon request, out of the scheduled protocol they did not reach the stone free status after one (n = 5), two (n = 6), or three sessions (n = 5), because it was hard to tolerate it despite Tamsulosin 0.4 mg/day along the whole period when they had the stent in place and Lornoxicam 8 mg/day, 10 days after each shock wave lithotripsy (SWL)
In order to avoid biases, these patients were excluded from the study. 12 cases with opinion differences regarding the results of SWL, as evaluated by KUB and ultrasound, were debated in order to achieve consensus
Summary
JJ stents are often encountered in patients with pelvic renal stones referred for shock wave lithotripsy, most of them being placed either for obstructive renal pelvic stones or for ureteric stones mobilized retrograde during the JJ stent insertion. Size and composition are essential factors that influence SWL outcome (Türk et al 2014; Rao et al 2011; Stoller and Meng 2007; Rassweiler et al 2011; Pilar Laguna Pes et al 2010; Tiselius 2009; Argyropoulos and Tolley 2007; Saigal et al 2005; Krishnamurthy et al 2005; Pareek et al 2005; Seitz et al 2006; Weld et al 2007). From the absence of the bubbles in the coupling medium, to the skin-to-stone distance and the stone density, all of these factors influence the physical processes of shock wave transmission and stone disintegration
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