Comparative Investigations on the Retrieval Capabilities of Various Baskets and Graspers in Four Ex Vivo Models

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1 European Urology European Urology ) 406±410 Comparative Investigations on the Retrieval Capabilities of Various Baskets and Graspers in Four Ex Vivo Models Taras Ptashnyk *, Armando Cueva-Martinez, Maurice Stephan Michel, Peter Alken, Kai Uwe KoÈhrmann Department of Urology, Klinikum Mannheim ggmbh, D Mannheim, Germany Accepted 11 February 2002 Abstract Objectives: The increasing application of ureterorenoscopy for the treatment of urolithiasis has produced a myriad of different help-tools for stone retrieval. In this study, we compared the retrieval capabilities of different baskets and graspers in ex vivo models and attempted to nd the most appropriate tool for stone extraction considering the location and size of stone, number of stones and potential harm to urinary tract tissue. Methods: We created four different ex vivo models with porcine kidneys and ureters and natural human stones: 1) single ureteral stone 4 mm); 2) single impacted ureteral stone 6 mm); 3) Steinstrasse; 4) single lower-pole stone 5 mm). With the aid of four baskets of different design at-wire basket Segura and Nitinol basket Zerotip, helical Gemini, and Parachute) and three graspers two-prong, three-prong Tricep, and Nitinol grasper Graspit) we performed repeated stone extraction 10 times in each model. The time for complete stone removal was calculated. Macroscopical evaluation of tissue was performed after each series. In the Steinstrasse model the frequency of instrument reinsertion into the ureter was also calculated. Results: In the single ureteral stone model, the fastest stone removal was achieved with the two-prong graspers, three-prong graspers and helical basket 20, 26 and 31 s, respectively). Segura and Parachute needed more time 55 and 86 s, respectively). Impacted stones were removed fastest with the two- and three-prong graspers 38 and 52 s, respectively), Segura and Gemini were slower 89 and 114 s, respectively). The Steinstrasse was cleared fastest by the helical basket with the lowest frequency of endoscope reinsertion 66 s, 1.4 reinsertion). The Segura, 149 s with 3.2 reinsertion was needed for the same procedure. With the Parachute and two-prong graspers 163 s, 1.8 reinsertion and 261 s, 4.6 reinsertion were needed, respectively. During postprocedural macroscopical evaluation of uretral tissue, the Parachute basket and three-prong graspers demonstrated the highest risk of mucosal and muscle. In the lower-pole kidney model, the poor de ectability of the ureterorenoscope prevented access to the lower-pole with the two- and three-prong graspers. There was no signi cant difference in stone retrieval time between the remaining Nitinol basket Zerotip and Nitinol grasper Graspit 87 and 61 s, respectively ). The number of failures was 4/10 for Zerotip and 5/10 for Graspit. No signi cant mucosal was noted with these tools. Conclusions: Our ex vivo models demonstrated that the design of graspers and baskets affects the time of stone retrieval in different situations and causes the various grades of tissue. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Flexible ureterorenoscopy; Baskets; Graspers 1. Introduction * Corresponding author. Tel.: ; Fax: address: ptashnykt@hotmail.com T. Ptashnyk). Ureterorenoscopy became one of the most important options for the treatment of urolithiasis. The stone extraction or clearance procedure is either carried out in one single step or follows stone disintegration /02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S )

2 T. Ptashnyk et al. / European Urology ) 406± A large variety of stone retrieval instruments, e.g. baskets and graspers, has been developed for this purpose. These instruments vary in design, function and effectiveness. Unfortunately, published information on the technical features and properties of differently designed stone retrieval instruments is lacking. One comparative report has been made on the capture and removal of stones by baskets [1]. In this study, stone retrieval with baskets was only investigated in a plastic model with inserted beads acting as stones. Graspers were not included in the evaluation and tissue was not assessed. One more comparative trial was performed with a porcine-kidney model [2]. But in this study only at-wire basket and nitinol basket were compared concerning ef cacy and safety of stone extraction in the kidney. We attempted to determine the ef cacy of the above mentioned instruments and to evaluate the amount of caused by them. We therefore, investigated and compared the retrieval capabilities of various baskets and graspers in four ex vivo models. 2. Materials and methods We established four ex vivo models consisting of freshly slaughtered porcine kidneys common pig breed) with intact ureters minimum length 20 cm) and natural human stones. 1. Single ureteral stone 4 mm). 2. Single impacted ureteral stone 6 mm). The effect of impactation was simulated with slight pressure on the ureter near the stone by an elastic bandage. The 1 cm wide bandage was Table 1 properties Number of wires/prongs Sheath diameter F) Flat-wire basket Parachute basket Helical basket 4 a Nitinol basket Two-prong graspers Three-prong graspers Nitinol graspers 2 b a Pairs. b Oval. Length cm) stretched around the ureter at a permanently fixed length of 1.8 cm in each series.) 3. Steinstrasse four stones 1±4 mm along the ureter one behind the other). 4. Single lower-pole stone 5 mm). Two urologists in training experienced in using graspers so far as baskets performed repeated stone extractions utilising four baskets and three graspers 10 repetitions in each model) see Figs. 1 and 2, Table 1). The length of the stone removal procedure and the number of endoscope reinsertions in the ``Steinstrasse'' model) was evaluated. The semiquantitative macroscopic evaluation of the tissue injury after each series was performed Table 2). The choice of instruments for each model was based on the technical recommendations of the distributors, logical considera- Table 2 Semiquantitative assessment of tissue Less than 2 mm mucosal lesions More than 2 mm con uated mucosal lesions Signi cant mucosal and muscle lesions Fig. 1. Baskets for stone retrieval. Fig. 2. Graspers for stone retrieval.

3 408 T. Ptashnyk et al. / European Urology ) 406±410 tions and experience gained in our department. All tool measurements were given in the manufacturers' technical speci cations and con rmed by manual measurements. Stone removal with baskets: 1. the closed basket was inserted to a point beyond the stone; 2. the basket was then opened and the stone manoeuvred into it; 3. the basket was closed with the stone inside; 4. the complete instrument was removed from the ureter. Stone removal using graspers: 1. the graspers were inserted distally in front of the stone and the prongs opened; 2. the stone was then manoeuvred between the prongs; 3. the complete instrument was finally withdrawn from the ureter. The period of time that elapsed between the opening of the graspers or basket and the point of complete removal was assessed. The inability to remove the stone within 3 min was considered a failure. Trials in the porcine ureter were performed with a semirigid 7.5 F Storz endoscope and in the kidney with a exible 7.5 F Storz endoscope. The two-prong graspers were provided by Storz, Germany, the remaining tools were provided by Boston Scienti c Microvasive, USA. The whole spectrum of investigated instruments was comparable in structure and function with instruments from another companies. 3. Results In the ureteral model with a single 4 mm stone, all instruments successfully retrieved the stone in each of the 10 repetitions. The mean time of stone retrieval for each instrument is given in Table 3. Following stone removal with the Parachute basket and the three-prong graspers, evaluation of the state of the tissue revealed distinct to the tissue of the ureters. In the ureters with an impacted 6 mm stone, the atwire basket failed in one repetition to retrieve the stone and the three-prong graspers failed in three repetitions Table 4). The three-prong graspers caused the most severe to the ureteral tissue. There was no failure during removal of the steinstrasse. The procedural time and number of repetitions are given in Table 5. Signi cant tissue was caused during extraction of the Steinstrasse by the Parachute basket. Standard graspers were used with less severe. Table 3 Results with the single uretral stone model time Flat-wire basket 0:55 0:25 Parachute 1:26 0:32 Helical basket 0:31 0:14 Two-prong graspers 0:20 0:11 Three-prong graspers 0:26 0:15 Table 4 Results with the impacted uretral stone model Four out of 10 failures were noted with the Nitinol basket in the lower-pole kidney model and ve out of 10 with the Nitinol graspers. Another instruments did not allow suf cient de ectability of the endoscope, hence preventing access to the lower calyx Table 6). No signi cant tissue of the ureter or the calyx was observed in these series. 4. Discussion time Number of failures Flat-wire basket 1:54 0:57 1 Helical basket 1:29 0:44 0 Two-prong graspers 0:38 0:30 0 Three-prong graspers 0:52 0:35 3 Table 5 Results with the steinstrasse model time number of reinsertions Flat-wire basket 2:29 0: Helical basket 1:06 0: Parachute 2:43 1: Two-prong graspers 4:21 2: Table 6 Results with the lower-pole kidney model time Numbr of failures Nitinol basket 1:37 0:47 4 Nitinol graspers 1:11 0:49 5 Nowadays, despite worldwide acceptance of ESWL as a rst-line treatment modality for stones, ureterorenoscopy is becoming increasingly popular in the treatment of nephrolithiasis. In accordance with the Clinical Guidelines Panel by Segura [3], patients with uric acid, cystine stones and distal ureteral stones should be considered candidates for primary URStreatment. This recommendation is also supported by Peschel et al. [4], who demonstrates in his prospective randomised study covering 80 cases of distal ureteral stones, that ureteroscopy was signi cantly better in terms of operative time, uoroscopy time and the stone-free state achievement time than ESWL. Ureterorenoscopy should also be carried out in patients with ureteral stones larger than 1 cm in size [3].

4 T. Ptashnyk et al. / European Urology ) 406± Lower-pole calyx stones with a distinctly lower stone clearance rate, even after multiple re-eswl treatments present a further crucial problem. This applies in particular to patients with unsuitable spatial anatomyðacute infundibulo-pelvic angle, long and narrow infundibulum. Abdelhamid [5] reports a decline in the stone-free rate in suchcasesfrom44downto16%. In contrast, Grasso and Ficazzola demonstrate in their prospective study [6] a success rate of 94% and 95% in the treatment of lower-pole stones smaller than 10 and 20 mm, respectively with exible ureterorenoscopes. Neither the lower-pole infundibulo-pelvic angle nor the degree of dilation of the collecting system in uenced the outcome of this trial. It should also be taken into account that permanent improvement of the technical properties of URS instruments downsizing, enhanced manoeuvrability) and the appropriate utilisation of retrieval instruments enhance ef cacy and safety during URS [7]. Stone extraction is the most decisive step in stone retrieval by ureterorenoscopy and distinctly in uences the procedural time, effectiveness and safety of endoscopical stone management. For the above-mentioned reasons, we conducted trials to compare the functional capabilities and potential side effects of various stone retrieval instruments. The main aim of our study was the standardisation and optimisation of the stone extraction procedure. We included the section of the porcine bladder with the intramural ureter in the initial stage of our trails. However, the antire ux mechanism in pigs functions differently to that in humans. In pigs, it is found in valve form and there is no narrowing at this point. Uptil now, there exists no model to simulate the narrow ori ce. The choice of instruments varied for each model. The low ef cacy and high risk of tissue in the single ureteral stone case made evaluation of the Parachute basket unnecessary in the similar impacted stone model. The low ef cacy of two-prong graspers in the steinstrasse model caused by the high number of reinsertions into the ureter made the evaluations of three-prong graspers super uous. The decrease in the de ectability of exible ureterorenoscopes with the above listed tools allowed evaluation of only the nitinol basket and nitinol graspers in the lower-pole model. Report by Honey [2] revealed that the Nitinol basket was superior to the at-wire basket in the middle and upper calyx and it is exclusive use in the lower calyx was one more reason for our choice in this model. The outcome of our trials demonstrated that the ef cacy of each instrument diverges and we hope that our observations could therefore be of practical and clinical value. We recommend the use of the classical two-prong graspers for single stone retrieval either impacted or non-impacted). This is a very economical method as this type of graspers is found in all presentday endourological armamentarium. If preference is given to baskets, we recommend the helical basket procedure, which is quite fast, effective and harmless. Caution should be exercised with the use of the three-prong graspers, as, despite the short duration of the procedure, they can cause severe to the ureteral tissue. There was a decline in the ef cacy of the two-prong graspers in the management of the steinstrasse with a consequent high number of reinsertions that caused extensive to the ureteral tissue. The use of the helical basket is appropriate in such cases, as stones positioned one behind the other can be ef ciently captured and safely withdrawn through the ureter without repeated reinsertions. Although the parachute basket effectively captures the stones, its use is not advisable owing to the high risk of ureteral injury caused during passage through the ureter. Taking into account that all other instruments do not reach the lower-pole, the endourologist should strictly adhere to either the calyx-adapted tipless basket or the oval-prong graspers. Our investigations did not reveal any signi cant superiority between these two tools. The stone size, eventual interruption of the procedure by releasing the stone and personal preference should be taken into consideration to ensure the correct choice of instrument. There was no occurrence of trapped basket in our investigations. This can be explained the maximal stone size 6 mm impacted stone model), which did not signi cantly extended the diameter of ureteral lumen. During Steinstrasse clearance, the stones were easily placed one behind the other within the basket. This was especially well demonstrated with the Parachute and helical basket. We do not have also forget the clinical cases when unskilled handling has resulted in trapped graspers that necessitated open surgery. For the above mentioned reasons, our results can not be directly introduced into clinical routine. Each case should be carefully considered before the choice of tool is made endoscopical assessment of the relationship between the size of stone and ureter; was the ureter prestented?; was the ostium dilated by the access sheath?). The results gained from our investigations will provide the young urologists with objective information on the correct choice of tool for different stone situations. They will also assist the experienced surgeon to make the best choice between instruments with similar function and in implementing his range of instruments.

5 410 T. Ptashnyk et al. / European Urology ) 406± Conclusions The choice of instrument for stone extraction can greatly in uence the ef cacy, safety and length of the stone retrieval procedure. The different technical features and functionality of this variety of tools for stone extraction should be carefully outweighed before their inclusion in routine clinical practice. References [1] El-Gabry EA, Bagley DH. Retrieval capabilities of different stone basket designs in vitro. J Endourol 1999;13 4):305±531. [2] Honey RJ. Assessment of a new tipples nitinol stone basket and comparison with an existing at-wire basket. J Endourol 1988;12 6):529±31. [3] Segura JW, Preminger GM, Assimos DG, et al. Ureteral stones clinical guidelines panel summary report on the management of ureteral calculi. J Urol 1997;158:1915±21. [4] Peschel R, Janetschek G, Bartsch G. Extracorporal shock wave lithotripsy versus ureterorenoscopy for distal ureteral calculi: A prospective randomised study. J Urol 1999;162:1909±12. [5] Elbahnasy AM, et al. Lower-pole caliceal stone clearance after shock wave lithotripsy, percutaneous nephrolithotomy and exible ureteroscopy: Impact of radiographic spatial anatomy. J Endourol 1998;12:113±9. [6] Grasso M, Ficazzola M. Retrograde ureteropyeloscopy for lower-pole caliceal calculi. J Urol 1999;162:1904±8. [7] Afane JS, Olweny EO, et al. Flexible ureterorenoscopes: A single centre of evaluation of the durability and the function of the new endoscopes smaller than 9 F. J Urol 2000;164 4):1164±8.