Endourology and Stones Comparative Experimental Evaluation of Guidewire Use in Urology Giovanni Liguori, Francesca Antoniolli, Carlo Trombetta, Matteo Biasotto, Antonio Amodeo, Giorgio Pomara, Stefano Bucci, and Emanuele Belgrano OBJECTIVES To evaluate the characteristics and mechanical properties of five different guidewires principally used in urology to provide a guide to the best choice in every situation. This objective was achieved by performing mechanical tests on each guidewire and on the same guidewire in relationship to a real human ureter. Finally, the mechanical properties of a real human ureter were evaluated experimentally. METHODS Five different guidewires with a 0.035-in. external diameter were studied to determine their mechanical properties of interest: tip buckling, shaft permanent deformation, guide friction on the human ureter, and the force at which the tip perforated a real human ureter. RESULTS Nitinol guidewires with hydrophilic coating had the least dangerous tip in the tip buckling and tip piercing force tests and the lowest friction values on the friction guide test. The shaft of the polytetrafluoroethylene-coated guidewires was stiffer on the bending resistance and plastic deformation tests. CONCLUSIONS The ideal endourologic guidewire should be sufficiently flexible and lubricated to negotiate a tortuous ureter and pass possible obstructions. However, high strength against bending is also required when we need to pass a stent or catheter over a guidewire. UROLOGY 72: 286 –290, 2008. © 2008 Elsevier Inc. A ccurate stent placement is greatly enhanced by proper ureteral access using a guidewire 1 ; how- ever, in the case of firmly obstructed or kinked ureters, endoscopic ureteral stenting can be a challenging procedure. 2–6 The performance of a guidewire is mostly influenced by its flexibility and the coefficient of friction of its coating. Clayman et al. 7 compared nine guidewires in an in vitro setting, specifically with regard to their use for access and as an inner guide for the coaxial passage of ureteral catheters stents. Ceschinski et al. 8 analyzed the torsional rigidity of 13 different commercial guidewires. In a recent study, Patriciu et al. 9 presented an objective method for testing guidewires and catheters that emulates the actual surgical environment using a computer-controlled test. The aim of the present study was to offer another critical evaluation by comparing the mechanical proper- ties of five different guidewires commonly available in our department. MATERIAL AND METHODS Five different guidewires with a 0.035-in. external diameter were tested (Table 1). Guide 1 was a 3-cm flexible tip polytet- rafluoroethylene (PTFE)-coated guidewire (Boston Scientific, Natick, Mass); guide 2, a Radifocus guidewire M (Terumo Europe N.V., Leuven, Belgium); guide 3 a PTFE guidewire (Medtronic, Danvers, Mass); guide 4, an Emerald Guidewire (Cordis, Miami, Fla); and guide 5, a Sensor Dual Flex (Boston Scientific). The mechanical properties of the guides were assessed using four different tests to simulate some operative urologic situations. More- over, the guides were tested using real ureters obtained from five consecutive autopsies. The ureters were cleaned and kept in saline solution; the tests were performed within the first 12 hours after autopsy. All mechanical tests were performed using a universal me- chanical testing machine (Galdabini Sun 500, Galdabini, Va- rese, Italy). In each experiment, five measures were performed for each guide. New guidewires and ureters were used in each test. The tip buckling test was performed to analyze the force required to bend the tip of the guide when encountering an obstacle. The guidewire was pushed against a fixed solid surface, and the minimal force at which guide buckling occurred was recorded. To investigate the resistance of the guide shafts to bending and the force at which their permanent deformation occurred, the three-point bending test was done. An 8-cm-long segment from the end of each guidewire was obtained and tested as the beam of a three-point bending test. The bending resistance of From the Departments of Urology, and Biomedicine, Unit of Dental Sciences and Biomaterials, University of Trieste, Trieste; and Department of Urology, S. Chiara Hospital, Pisa, Italy Reprint requests: Giovanni Liguori, M.D., Ph.D., Department of Urology, Uni- versity of Trieste, Strada di Fiume 447, Trieste 34144 Italy. E-mail: gioliguori@libero.it Submitted: September 5, 2007, accepted (with revisions): December 9, 2007 286 © 2008 Elsevier Inc. 0090-4295/08/$34.00 All Rights Reserved doi:10.1016/j.urology.2007.12.098