Introduction and Objective Comparison of insertion forces during ureteral access sheath placement in an experimental model with different commercially available access sheaths Tefik T.1, Buttice S.2, Marson F.2, Sanli O.1, Oktar T.1, Villa L.2, Traxer O.2, PETRA UroGroup, Paris, France 1Istanbul University, Istanbul Faculty of Medicine, Urology, Istanbul, Turkey, 2Pierre et Marie Curie University, Paris VI, Tenon University Hospital, Urology, Paris, France Introduction and Objective Materials and Methods A special water tank was designed to insert the UASs into SCAs (ex-vivo ureteral orifices) with 3 different diameters of 10Fr (SCA-1), 8Fr (SCA-2) and 4Fr (SCA-3). Four different brands of UAS with different diameters (9.5-11.5, 10-12, 10.7-11.7, 11-13, 12-14 Fr) were used and codes UAS-1 to 11 were given to each UAS. Three investigators [Inv-1(experience <30 cases), Inv-2(experience <30 cases), and Inv-3(experience 300 cases)] performed the trial 5 times for each catheter and SCA. All of the UASs were traditional coaxial sheaths, except two (10-12 and 12-14 Fr) designed for lateral insertion and single wire use. Testing was performed with the same guidewire and safety wire (Straight, Stiff Type, 0.035 inch, 150cm, 3cm FLEX L, Terumo, Radifocus®, Leuven, Belgium). The UASs were fixed to a load cell and the IF was continuously recorded with a digital force gauge (DFS II, Chatillon®, Ametek® Test and Calibration Instruments, Largo, Florida, USA) during placement with constant speed of 25mm/sec. Every UAS was compared regarding IF with the other UASs using the 3 SCAs. Each UAS was given a point according to the following criteria; [(+1): UAS had significantly lower IF value when compared with another UAS, (-1): UAS had significantly higher IF value, (+0.5): UAS had lower but not significant IF value when compared with another UAS, (-0.5): UAS had higher but not significant IF value]. The UAS with the higher points were considered to be less traumatic and rank on the top of the list. In the recent years, retrograde intra-renal surgery (RIRS) has become a significant option in the treatment of upper urinary tract diseases. 1, 2 Either treating a stone or ablating a tumor intra-renally, the use of ureteral access sheath (UAS) has always been a matter of debate. Even though UAS is an important tool allowing direct access to the kidney, facilitating the insertion of endoscopes into the renal collecting systems, permitting multiple entry and re-entry while decreasing the intra-renal pressure and improving the drainage around the scope there is no clear recommendation as to their use during RIRS. 3-7 Nonetheless, the practices may change following the report of Cindolo et al. regarding the mortality of 6 patients after RIRS, where 4 cases were performed without UAS use. 8 Ureteral access sheaths offering a reduced intra-renal pressure are helpful preventing pyelovenous and pyelolymphatic backflow, protecting from the risk of bacterial dissemination during RIRS. 6 The ability to place an access sheath into the ureter is dependent on the coefficient of friction of the sheath surface and the axial force that results in buckling of the sheath at the ureteral orifice.9 To our knowledge, the external force [or insertion force (IF)] applied by the surgeon in order to place an UAS has not been previously measured during insertion. This IF, if measured, would guide the surgeons not to place an UAS whenever ureteral damage risk would be anticipated or proceed safely in case of no risk. In the present report we aimed to measure the force necessary to win the resistance during insertion of ureteral access sheaths (UAS) in experimental ex-vivo mechanical orifice model using various caliber sealing cap adaptors (SCA) and to compare different commercially available UASs regarding to this insertion force (IF). Results There was difference among experienced and inexperienced surgeons using SCA-1 in UAS-1, 4, 7 and using SCA-2 in UAS-1, 5, 7, 9 and 11. SCA rupture was observed with SCA-3 using all UASs, except UAS- 1. UAS-1 had significantly lower IF compared to UAS-3, 5, 6, 7, 8, 9, 10 and 11 with the SCA-1, whereas had significantly lower IF compared to UAS-3, significantly higher IF compared to UAS-4, 9 and 10 with the SCA-2 (p<0.05). UAS-2 had lower IF compared to UAS-5, 6, 7, 8, 9, 10 and 11 with SCA-1 and lower IF compared to UAS-7, 8, 9 with SCA-2. The IF did not correlate with increase in UAS and decrease in SCA diameter in every UAS. UAS-1 scored highest when using SCA-1, whereas UAS -8 had the lowest score. All 10 Fr UASs had higher scores than >10 Fr UASs. The 12 Fr UAS-10 had the highest score among 12 Fr UASs and had higher score than 10.7 and 11 Fr UASs. UAS-3 (10-12 Fr designed for lateral insertion) scored highest when using SCA-2, whereas UAS-9 (12-14 Fr designed for lateral insertion) had the lowest score. UAS-10 scored 3rd better than one 10 Fr, the 10.7 Fr and the 11 Fr UASs. The UAS with the smallest diameter was ranked 8th (Table-1). Rank UAS Code points w SCA-1 points w SCA-2 1 9 3 8.5 2 7.5 4 7 6.5 10 5.5 3.5 5 0.5 11 1.5 6 -1 -2.5 -1.5 8 -4 -3 -5 -4.5 -6.5 -7.5 -8.5 -9.5 Picture 1 and 2.- Above, the 8 and 10 Fr adaptors. Right, the experimental ex-vivo water tank model to insert UAS in an isotonic fluid milieu using guide wire. The model is made by plexiglass using 5mm laparoscopic ports. Table 1.- Left, rank of UAS with SCA-1 and SCA-2. Conclusions The UAS commercially designated diameter and SCA caliber are not the only factors determining the IF during UAS placement. Other parameters such as hydrophilic coating and the actual diameter of UASs should be taken into consideration. The clinical relevance of the UASs' IF needs to be defined. 1.Haddad, M., Cloutier, J., Cornu, J. N. et al.: Immediate Nephroureterectomy or After Attempting Conservative Treatment, on Elective Indications, for Upper Urinary Tract Urothelial Carcinoma: Comparison of the Pathology Reports on a Retrospective Monocentric Study. J Endourol, 2015 2.Doizi, S., Letendre, J., Bonneau, C. et al.: Comparative study of the treatment of renal stones with flexible ureterorenoscopy in normal weight, obese, and morbidly obese patients. Urology, 85: 38, 2015 3.Traxer, O., Wendt-Nordahl, G., Sodha, H. et al.: Differences in renal stone treatment and outcomes for patients treated either with or without the support of a ureteral access sheath: The Clinical Research Office of the Endourological Society Ureteroscopy Global Study. World J Urol, 2015 4.Kourambas, J., Byrne, R. R., Preminger, G. M.: Does a ureteral access sheath facilitate ureteroscopy? J Urol, 165: 789, 2001 5.L'Esperance J, O., Ekeruo, W. O., Scales, C. D., Jr. et al.: Effect of ureteral access sheath on stone-free rates in patients undergoing ureteroscopic management of renal calculi. Urology, 66: 252, 2005 6.Stern, J. M., Yiee, J., Park, S.: Safety and efficacy of ureteral access sheaths. J Endourol, 21: 119, 2007 7.Auge, B. K., Pietrow, P. K., Lallas, C. D. et al.: Ureteral access sheath provides protection against elevated renal pressures during routine flexible ureteroscopic stone manipulation. J Endourol, 18: 33, 2004 8.Cindolo, L., Castellan, P., Scoffone, C. M. et al.: Mortality and flexible ureteroscopy: analysis of six cases. World J Urol, 2015 9.Monga, M., Gawlik, A., Durfee, W.: Systematic evaluation of ureteral access sheaths. Urology, 63: 834, 2004 EAU Munich, 2016 Poster Number 124