Evaluation of a free 3D software for kidney stones’ surgical planning: “kidney stone calculator” a pilot study

Abstract

Introduction Kidney Stone Calculator (KSC) is a free, three-dimensional (3D) planning software for flexible ureteroscopy(fURS) with Holmium:YAG(Ho:YAG) endocorporeal lithotripsy (EL). KSC provides the stone volume (SV) and expected duration of lithotripsy (ExDL) estimations based on non-enhanced-CT scan (NECT) DICOM series. We aimed to provide a preclinical and clinical evaluation of KSC. Patients and methods A preclinical evaluation measured the SV by three operators (resident, endourology expert and research engineer) among 17 NECT cases. Between January and March 2020, a multicentric, prospective, observational double-blind clinical evaluation was conducted in patients presenting with renal stones treated with Ho:YAG-EL during fURS and preoperative NECT. Demographic and surgical data were collected. The primary endpoint was a significant median difference between ExDL and EffectiveDL (EfDL). Second, efficiency (J/mm 3 ) and efficacy (mm 3 /min) ratios were calculated. Results The preclinical evaluation showed no significant difference in the SV measurements among operators ( p > 0.05). Pearson and Kendall coefficients of 0.99 and 0.98, respectively, were found. Twenty-six patients were included in the clinical evaluation, with a median age of 55 years. In 66% of cases, there was a single stone located in the lower pole, with a density > 1000 Hounsfield Unit observed in 42% and 85% of cases. A 14% [Q1–Q3 (5.4–24.8); p = 0.36] median difference between ExDL and EfDL was noted, which was greater in the case of lower pole stones with no possible relocation ( p = 0.008). Median values of 17.6 J/mm 3 and 0.4 (0.32–0.56) mm 3 /s EL were also noted. Conclusions Kidney Stone Calculator is a reproducible and accurate software that allows for an estimation of the stone burden and provides an ExDL for URSf. Defining the influencing factors of EL will improve its ExDL. Supplementary Information The online version contains supplementary material available at 10.1007/s00345-021-03671-z.

Laser Fiber Displacement Velocity during Tm-Fiber and Ho:YAG Laser Lithotripsy: Introducing the Concept of Optimal Displacement Velocity

“…We have emphasized the laser factors and laser fiber working distance that could have influenced the ablation efficiency, but other intra-operative factors must be noted. The surgeon’s technique and ability to dust stones necessarily has a major role in stone ablation, as the required efficacy (J/mm 3 ) and efficiency (mm 3 /s) ratios are respectively lower and higher in expert centers compared to non-expert ones [ 7 , 9 ]. The stone composition could also influence ODV.…”

“…As a result, we could suggest a lower ODV in soft stones (uric acid, calcium oxalate dihydrate and struvite). Furthermore, the production of significant fragments that would require basketting during flexible ureteroscopy is often correlated with the surgeon’s technique or experience or the laser parameters [ 4 , 6 , 7 ]. Consequently, operating at the ODV could help to minimize the risk of fragments’ production, and the time-consuming basketting duration (25% of the procedure) [ 7 ].…”

“…Furthermore, the production of significant fragments that would require basketting during flexible ureteroscopy is often correlated with the surgeon’s technique or experience or the laser parameters [ 4 , 6 , 7 ]. Consequently, operating at the ODV could help to minimize the risk of fragments’ production, and the time-consuming basketting duration (25% of the procedure) [ 7 ]. Finally, any surgeon has to displace the laser fiber at the stone surface according to the endoscopic vision and the produced fragments in order to avoid mucosa injuries.…”

“…We could have also used the characteristics of the ablated crater: deepness, width, length and produced fragments’ size. Consequently, even if our method has been validated by previous in vitro and in vivo studies, we could have analyzed the stone samples using a profilometric method [ 4 , 7 , 9 , 15 , 24 ]. A further dedicated experiment should directly compare both profilometric and three-dimensional segmentation methods.…”

“…Overcoming this technologic comparison, the efficiency determinants of ELL have not yet been fully demonstrated. If international recommendations recognize two influencing factors: stone size, i.e., maximum diameter and stone density (Hounsfield units), additional determinants are suggested: stone volume, stone location, laser source and laser settings, consumable (laser fiber, ureteroscope, pumping system, ureteral access sheath) and lithotripsy method (dusting technique, pop-dusting and pop-corning) [ 7 ]. Considering the dusting technique, the painting method is widely acknowledged, with the one pulse-on locus objective to avoid the burnback effect and the production of significant fragments, and to optimize the ablated stone volume [ 8 ].…”