Urolithiasis is regarded as a common disease in Urology Department with increased incidence, and the recurrence rate is high (over 50% within 5 years), thus bringing tremendous financial burdens for patients(4, 5). In recent years, the minimally invasive technique for treating urolithiasis has been developed rapidly. Particularly, the flexible ureteroscopy has been extensively applied in the real world(6). For flexible ureteroscopy, the ideal perfusion equipment should possess three requirements. The first one is that it should guarantee a clear field of view, the second is that it should avoid the excessively-high renal pelvic pressure, the third is that it should be flexible, simple to operate, cost-effective, and highly stable(7). Currently, there are three used perfusion methods, including automated irrigation systems, gravity-based irrigation systems and syringe-based hand-held or foot-pump irrigation systems. Especially, the simple syringe is applied in syringe injection for manual injection. The perfusion pressure can be adjusted timely and intraoperatively according to the needs of the view field and surgical operations. For example, the washing pressure was appropriately increased to change calculus position and pyuria suction. In this way, the intrapelvic pressure can be effectively controlled, guaranteeing the safety and efficiency of surgical operation(8–10).
Generally, 50 ml syringe and infusion apparatus extension tube are used for manual injection of liquid in ordinary syringe perfusion. The used equipment is simple and low-cost, while it is limited by the syringe volume. Moreover, the syringe needs to be replaced or re-filled frequently, which leads to repeated interrupted perfusion. As a result, it has a negative impact on the operation and remarkably increases the workload of assistants. By contrast, autonomous perfusion equipment prepared in this study realizes continuous and uninterrupted perfusion; meanwhile, because the syringe can be rapidly and automatically filled with the single-hand operation, the hand fatigue induced by the frequent operation can be avoided.
Compared with other hand-held irrigation systems (like single action pumping system, Boston Scientific and Irri-flo irrigation delivery system, Gyrus ACMI and Olympus), the perfusion equipment assembled in this study exhibits more advantages in addition to the construction of an efficient and simple irrigation pathway. First, the assembled materials are commonly used devices in routine practice, which can be easily obtained and will not be affected by hospital conditions and policy. As a result, most doctors can easily assemble this equipment. Among them, the negative pressure spring frequently used in cosmetic surgery is durable and flexible. Its head and tail ends can be perfectly embedded into a syringe(11). The Luer one-way valve is made of the polycarbonate material with high strength and favorable durability. In addition, it can be used at a wide range of temperatures (-60-120℃) for a long time, and can withstand stream, cleaning agent, heating and high dose radiosterilization. Therefore, it has been extensively applied in the hemodialysis device, surgical mask as well as infusion piping system(12, 13). Its front cracking pressure is less than 0.5 Kpa, and the maximum back pressure is larger than 0.3 MPa, which effectively realizes the one-way flow of perfusate. Another advantage is that the cost for preparing the whole equipment is low (less than 10 dollars in China), which is far lower than that of other single-action-pump systems (over 150 dollars in China). In this way, it remarkably reduces financial burdens of patients. The negative pressure spring can be recycled after disinfection without compromising physical properties. In most countries, other irrigation systems like SAP with high prices are imported, which restricts their practical application. Moreover, the seal valve of the SAP system is easily to be ruptures and isolated after long-term usage. When the vacuum system is destroyed, a new set of perfusion equipment should be replaced, which evidently increases the operation cost(2). The designed device in this study is not dependent on the vacuum system, and it can be disassembled at will. Moreover, the cost will not be substantially increased if the parts are replaced during the surgery. It is easy to assemble this perfusion device, and the ports of each device are universal Luer ports, which can tightly fit with each other and guarantee the superior system leakproofness. In addition, the assembled equipment in this study can flexibly configure other devices based on intraoperative needs. For instance, by bridging another three-way valve, rotating the regulating valve and adjusting the position of the one-way valve, real-time regulation of functions of manual irrigation, continuous perfusion, and negative pressure suction can be realized, which greatly enhances the operation efficiency and shortens the operation time.
Similar to other syringe perfusion equipment, the drawback of this equipment is that an assistant is needed for water injection. The cooperation of the assistant is the key to inducing intrapelvic pressure changes during the flexible ureteroscopy lithotripsy process. An experienced assistant should be familiar with each surgical step and endoscopic surgical process, and he/she is able to flexibly regulate the water injection pressure and reduce the perfusion flow while guaranteeing the smooth operation(14). Additionally, long-term application of the perfusion equipment also leads to the issue of hand fatigue, which may result in transient intrarenal hypertension. In addition, the equipment performance of assembled equipment may be reduced after a long-term operation, and the equipment should be replaced as required. In this study, a method to prepare the endoscopic perfusion equipment is proposed, and the equipment stability and safety should be further investigated.