Prospective, Randomized Trial Comparing Soft and Firm Ureteral Stents

Study Design and Patient Selection

• Study Period and Ethical Approval:

• Conducted between July 2023 and July 2024 following institutional review board approval (SMC 0119-23).
• Informed consent obtained from all participants.
• Adhered to the Declaration of Helsinki.
• Stent Types and Randomization:

• Soft stent: Universa® (Cook Medical).
• Firm stent: Percuflex™ Plus (Boston Scientific).
• Randomization in a 1:1 ratio using asymptomatic maximal randomization.

Surgical Technique and Intervention Operative Team included three fellowship-trained endourologists.

Procedure Details:

• Ureteroscopy performed using standard 6.5/8.5Fr semi-rigid ureteroscope.
• Lithotripsy performed using a 120W Holmium:YAG laser (0.3 Joule, 40 Hertz, dusting technique).

Stent Placement was performed using a 0.038 Inch glide wire. 6Fr stents used, either soft or firm polymer material, according to randomization.

Proximal stent curls positioned in the upper calyx/renal pelvis; distal curls in the bladder.

Postoperative Care Stent removal was scheduled 2 weeks post-procedure, ans performed using a flexible cystoscope in the outpatient clinic.

Symptoms assesed using the Ureteral Stent Symptoms Questionnaire (USSQ) that was completed at the stent removal visit.

Statistical Analysis

• Sample Size Calculation:

• Based on a 3-point difference in USSQ index score between groups.
• Assumed 5% type I error and 80% power.
• Adjusted for a 10% dropout rate; target sample size: 140 patients.
• Data Blinding:

• Patients, data collectors, and analysts blinded to allocation.
• Since blinding the surgeons to stent type was impossible, surgeons were not involved in data collection or analysis.
• Analysis Methods:

• Continuous variables: Mann-Whitney U test; median and IQR.
• Categorical variables: Pearson's chi-square or Fisher's exact test; frequencies and proportions.
• Multivariate linear regression for USSQ index and urinary domain scores.
• Statistical significance set at p<0.05.
• Analyses conducted using IBM SPSS v26.

This protocol ensures a rigorous and reproducible methodology for evaluating the impact of stent type on patient-reported outcomes following ureteroscopy and lithotripsy.

Inclusion criteria

• patients aged over 18 years
• ureteral stones measuring up to 2cm requiring URS and laser lithotripsy

Exclusion criteria

• pediatric patients
• bilateral stones requiring bilateral URS and laser lithotripsy,
• stone located in the renal pelvis or calyces,
• intra-operative complications of any kind,
• any residual stones during the procedure,
• ureteroscopies in which no stones were treated ("white ureteroscopy").