Ureteral stricture disease (USD) is an increasingly common urologic disease with variable causes including ureterolithiasis, injury, retroperitoneal fibrosis, or abdominopelvic malignancies [1]. Ureteral stricture disease can impair renal function and lead to some symptoms like flank pain, nausea, infection, vomiting, or urinary calculi. The treatment of USD includes surgical repair (open, laparoscopic, or robotic surgery) and endoscopic management (balloon dilation, endoureterotomy, chronic indwelling ureteral stent, or nephrostomy) [2], [3], [4]. No matter which therapeutic regimen was adopted, a ureteral stent will be applied after the operation.

The modern ureteral stent has been one of the most commonly used devices in handling urological diseases since 1978 introduced by Finney [5]. The main function of the ureteral stent was to stabilize the ureter and assist the outflow of urine, which made this tool vital. It was widely used to provide support for the ureter after treating urolithiasis, resolving the obstruction and other urinary diseases. However, implantation of the ureteral stent can meet some side effects. Building a bridge from the kidney to the bladder with a long foreign object can result in discomfort, infection, and encrustation on the surface of the stent. It was reported that >80% of patients suffered from the discomfort caused by the ureteral stent [6]. The distal stent loop of the modern ureteral stent hindered the normal function of ureteric orifice and increased the reflux of urine. At the same time, the bacterial colonization rate was ranged from 42% to 90%, which can also affect daily activities [7,8]. Similar to bacterial colonization, stent encrustation was also a common problem, especially in patients with long time stented with the ureteral stent. From the current evidence, encrustation occurs in 76.3% of stents removed after 12 weeks [9]. Due to these side effects, the ureteral stent cannot be stented permanently. It should be removed or replaced at a specific time. The procedure for traditional ureteral stent removal should be conducted in the hospital, and often causes physical discomfort, and injury to the urethra and adds an economic burden for patients. Therefore, the introduction of a modified stenting device that can support the ureter and drain urine without bringing any side effects was demanded.

An ideal stenting device should maintain the function and reduce the side effects of the modern ureteral stent at the same time. The widely used modern ureteral stent was a thin tube with a Double-J shape on either end to prevent upward or downward migration [10]. However, according to the evidence from the Ureteral Stent Symptom Questionnaire (USSQ) developed by Prof. Joshi, the positioning of the distal stent loop within the bladder was the cause of stent-associated discomfort [6]. To avoid the shortcoming of traditional ureteral stents, we modified the structure and material of the traditional ureteral stent. The first change was the length of the ureteral stent, we removed the Double-J shapes of the ureteral stent and shorten the length of the ureteral stent. Accomplished by the removal of the J structure was the reduction of stability. We introduced the balloon dilation technique to expand the modified mesh ureteral stent and made it adhere to the ureter with the purpose of improving the stability of stents. Then, we turned the tubular stent into the mesh stent, which can reduce the place for calcification to deposit theoretically. Finally, we introduced the biodegradable poly-L-lactic acid (PLLA) as the material of the mesh stent, which can avoid the second visit to hospital for removing the ureteral stent.

This research aimed to estimate the safety and effectiveness of the modified biodegradable mesh ureteral stent in treating ureteral stricture in vivo and in vitro.