This study investigates whether a modified Single-J ureteric stent (SJS) is a safe and better-tolerated alternative to the standard Double-J stent (DJS) following ureteroscopy (URS) for kidney and ureteric stone disease. Standard DJS are routinely placed after URS but frequently cause significant patient discomfort, including urinary urgency, frequency, pain, and haematuria. The SJS is created by modifying a commercially available Bander Ureteral Diversion Stent - retaining the proximal renal coil but removing the distal bladder loop - with the aim of reducing these lower urinary tract symptoms while maintaining adequate ureteric drainage and positional stability.

Eligible participants are adults aged 18 or older who are already pre-stented with a DJS and are scheduled for elective URS at Austin Health (Austin Hospital or Heidelberg Repatriation Hospital, Melbourne, Australia). At the time of URS, the existing DJS is replaced with the modified SJS. Participants complete a validated symptom questionnaire - the Ureteral Stent Discomfort Test (USDT) - both before URS (with DJS in situ) and at the time of stent removal approximately two weeks later (with SJS in situ), enabling a direct within-patient comparison. Stent migration is assessed cystoscopically at removal. The study aims to enrol 40 participants over approximately six months.

Background and Rationale Kidney and ureteric stones are among the most common urological conditions worldwide, frequently requiring surgical treatment via ureteroscopy (URS) - a minimally invasive procedure in which a thin camera is passed through the bladder and into the ureter to visualise and treat stones using laser energy. Following URS, it is standard practice to leave a ureteric stent in place for a period of one to four weeks. This stent is a small, flexible plastic tube that keeps the ureter (the tube connecting the kidney to the bladder) open, allowing it to drain freely while postoperative swelling resolves.

The most widely used stent is the Double-J stent (DJS), named for the curled "J" shape at both its upper (kidney) and lower (bladder) ends, which anchors it in position and prevents it from moving. While the DJS is clinically effective, it is well-documented to cause significant discomfort and interference with daily life. Patients commonly experience urinary urgency, increased frequency of urination, a sensation of incomplete bladder emptying, pelvic or flank pain, blood in the urine, and, in some cases, difficulty maintaining normal activity or sexual function. These symptoms stem largely from the lower curl of the DJS sitting inside the bladder, where it can irritate the bladder wall and trigone. Reducing these stent-related symptoms without compromising patient safety represents an important and unmet clinical need in endourology.

The Investigational Device This study evaluates a modified Single-J stent (SJS), created by adapting a commercially available Cook Medical Bander Ureteral Diversion Stent - a device ordinarily used in bladder removal (cystectomy) surgery. The modification involves shortening the stent to 28 centimetres from the proximal (kidney) curl, eliminating the distal bladder loop entirely. A 2-0 monofilament non-absorbable prolene suture is then anchored to the distal tip of the stent, measured to 7 centimetres, to aid retrieval. The resulting SJS retains its proximal renal coil for positional stability within the kidney, while the straight lower end rests within the bladder without forming the irritating distal loop characteristic of the standard DJS. The hypothesis is that the absence of this lower curl will meaningfully reduce lower urinary tract symptoms while maintaining adequate ureteric drainage and an acceptable safety profile.

Study Design

This is a prospective, single-arm, interventional feasibility study conducted at Austin Health, Melbourne, Australia, across two sites: Austin Hospital and Heidelberg Repatriation Hospital. The study uses a within-subject (before-and-after) design, meaning each participant serves as their own control. This approach is made possible by enrolling only patients who already have a standard DJS in place from a prior procedure, enabling a direct, paired comparison of symptoms between the two stent types within the same individual.

The study is non-randomised, as all eligible participants will receive the modified SJS. A target of 40 participants will be enrolled over an estimated six-month recruitment period. Each participant's involvement spans approximately three to four weeks in total.

Who Can Participate Eligible participants are adults aged 18 years or older who are already pre-stented with a standard DJS and are scheduled for elective URS and laser lithotripsy for ureteric stone disease. Patients must be willing and able to provide informed consent and have sufficient English proficiency to complete the symptom questionnaire. Individuals are excluded if they have a single functioning kidney, bilateral ureteric disease, a history of ureteric strictures or prior ureteric reconstruction, active urinary tract infection, pregnancy or breastfeeding, an immunocompromised state, or any contraindication to ureteric stenting or flexible cystoscopy. Patients with complex intraoperative findings - such as very large or impacted stones, stones in the intramural ureter, difficult stent insertion, or significant intraoperative bleeding - are also excluded to ensure participant safety.

What Participation Involves Participants complete a validated symptom questionnaire - the Ureteral Stent Discomfort Test (USDT) - on two occasions: first, prior to their URS while the existing DJS is still in situ, and second, at the time of stent removal approximately two weeks after URS while the SJS is in place. The USDT is a 13-item questionnaire covering six domains: urinary symptoms, pain, daily life impact, sexual life, analgesic and medical care use, and overall quality of life, with a total possible score of 61 points.

At the time of scheduled URS, the existing DJS is removed and replaced with the modified SJS, which is inserted under fluoroscopic guidance in standard fashion. The preoperative CT scan is also reviewed to measure ureteral length. Approximately two weeks after URS, participants attend for stent removal via flexible cystoscopy, during which the position of the SJS tip is directly visualised and categorised: freely floating in the bladder, at the ureteric orifice, in the urethra, or not visualised. This cystoscopic assessment represents the primary method of migration detection.

Throughout the stent-bearing period, participants are monitored for adverse events including urinary tract infection, haematuria requiring medical attention, emergency department presentations, hospital readmission, and need for early stent removal or re-intervention.

Outcomes The primary outcome is the rate of SJS migration, assessed cystoscopically at stent removal. A clinically acceptable migration rate is defined as 5% or less. The principal secondary outcome is the change in USDT total score from baseline (with DJS) to follow-up (with SJS), assessed using a paired t-test or the Wilcoxon signed-rank test depending on data distribution. Additional secondary outcomes include the incidence of stent-related complications, operative metrics such as insertion time and handling characteristics, and participant-reported satisfaction and willingness to undergo similar management in the future.

Ethics, Safety, and Data Governance The study has been reviewed and approved by the Human Research Ethics Committee (HREC) of Austin Health, and is conducted in accordance with the National Statement on Ethical Conduct in Human Research (2018) and Good Clinical Practice guidelines. Participation is entirely voluntary, and participants may withdraw at any time without impact on their ongoing care. All adverse events are recorded and managed promptly; serious adverse events are reported to the Austin Health HREC and Research Governance Office within 72 hours. Study data are stored securely in a REDCap (Research Electronic Data Capture) database hosted on a secure institutional server, identified only by a unique participant study number. Data will be retained for a minimum of 15 years following study completion. No financial incentives are offered to participants.

Inclusion Criteria:

• Age ≥ 18 years
• Undergoing elective ureteroscopy (URS) and stent exchange for ureteric stone disease
• Able and willing to provide written informed consent
• Sufficient English proficiency to complete the USDT symptom questionnaire

Exclusion Criteria:

• Single functioning kidney or bilateral ureteric disease
• History of ureteric strictures or prior ureteric reconstruction
• Pregnancy or breastfeeding
• Active urinary tract infection at time of URS
• Immunocompromised state (e.g. ongoing chemotherapy or high-dose corticosteroids)
• Any contraindication to ureteric stenting or flexible cystoscopy
• Unwilling or unable to comply with follow-up procedures
• Complex intraoperative findings precluding safe SJS insertion, including: ureteric stone >10mm, impacted stone, stone in the intramural ureter, difficult stent placement, or significant intraoperative haematuria

Individual participant data will not be shared. The study enrolls a small feasibility cohort of 28 participants, and despite de-identification measures, the combination of clinical and demographic variables carries a residual risk of re-identification. Data will be retained and governed under Austin Health institutional policies. Aggregate de-identified findings will be disseminated through peer-reviewed publication and conference presentation.