Design,fabrication And Experimental Study Of Flexible Ureteroscope Sheath With Variable Caliber

Background and objective:Flexible ureteroscope is an important medical equipment in urology,which has been widely used in the examination and treatment of renal pelvis and upper ureteral diseases.Ureteral access sheath are placed as the operation channel for ureteroscopy.At present,the diameter of the sheath is fixed,which means the diameter during operation is the same as that during insertion.In order to ensure that the flexible ureteroscope can pass through the ureter smoothly,the diameter of the sheath is large,causing great lateral friction and shear force.And ureteral injury,bleeding,avulsion and other complications are inevitably occurred.The ideal sheath should both have large operation diameter and small catheterization diameter in order to reduce ureteral injury,which can not achieve for the conventional sheath.Therefore,the purpose of this study is to put forward the theory of a variable caliber sheath: the diameter of the sheath is small to reduce the damage when it is inserted,the diameter of the sheath is large to operation after catheterization;two kinds of variable caliber sheaths are designed and manufactured,including "expandable and retractable ureteral sheath with locking device" and "water-ballon dilated ureteral sheath";the feasibility,practicability and safety of the new sheaths were verified through simulation model experiment and animal experiment.Methods:1.Design and manufacture of the sheath: the design parameters of sheath were determined according to human anatomy parameters;materials were selected and 3dsmax was used for sheath animation design;computer aided design(CAD)software was used to complete the industrial design;3D printing,blow molding,copying and other technologies were used to complete the sheath manufacture.2.Simulation model test: the urinary system simulation model was used to perform the insertion and extraction operation of new sheath.The statistical data included: the dilated effect of new sheath and the caliber before and after the sheath dilating.3.Animal experiment: the Chinese pigs were divided into new sheath group and conventional sheath group to undergo sheath insertion and extraction experience.The total time of operation,the resistance of sheath insertion and extraction,the diameter during catheterization,the success rate of sheath insertion,and the pathology of ureteral injury were recorded.Results:1.The design and manufacture of the expandable and retractable ureteral sheath with locking device were completed,but it was difficult to realize miniaturization.2.The design and manufacture of water-ballon dilated ureteral sheath were completed,and the miniaturization was realized successfully.3.The results of water-ballon dilated ureteral sheath in simulation model experience showed that it could effectively and evenly dilate the ureter,and the diameter of the sheath could reach the ideal requirements.4.The results of animial experience showed that the operation time,insertion time and insertion resistance of the new sheath were less than those of the traditional sheath,the outer diameter of the new sheath during insertion was smaller than that of the traditional sheath,and the success rate of the new sheath was higher than that of the traditional sheath.There were no significant differences between the two kinds of sheaths in the extraction time,extraction resistance and inner diameter after catheterization.Conclusion:The practice of the ureteral sheath with variable caliber is feasible.The water-ballon dilated ureteral sheath can realize the function of large operation diameter and small catheterization diameter.The new sheath simplify the insertion process,shorten the insertion time,improve the success rate of catheterization and reduce the tissue damage,which has the value of research and development.