Objective: To determine the stone-free rates after ureteroscopic lithotripsy (URSL) between patients who had large and small ureteral stent.
Material and Method: A prospectively randomized controlled study. Patients who underwent URSL between January 2014
and April 2015 were enrolled. Sixty eligible patients were randomized into 3 groups: non-stented as a control group (n = 20), 4.7 Fr stented (n = 20), and 6 Fr stented groups (n = 20). The lithotripsy technique was stone fragmentation using Holmium: YAG laser (LumenismodelTM) until the fragment was smaller than 2 mm. The stone fragments were left in situ without extraction. Primary outcome was stone-free rates detected by non-contrast-enhanced computed tomography (NCCT). Secondary outcomes were irritative symptoms evaluated by overactive bladder symptoms score (OABSS), flank pain, hematuria, urinary tract infection (UTI), auxiliary procedure, and readmission.
Results: The pre-operative characteristics of each group were similar. A stone-free rate in non-stented, 4.7 Fr stented, and
6 Fr stented groups was 95%, 85%, and 85% (p = 0.524), respectively. There was no statistically differences between 4.7 Fr and 6 Fr stented groups for irritative symptoms (25% vs. 45%, p = 0.185), flank pain (10% vs. 5%, p = 0.548), asymptomatic pyuria (35% vs. 25%, p = 0.288), febrile UTI (5% vs. 10%, p = 0.151) and hematuria (45% vs. 30%, p = 0.327). The operative time, postoperative pain, analgesic requirement, length of hospital stay, auxiliary procedures, and readmission were not different.
Conclusion: There was no difference in stone-free rates and stent-related adverse effects between small and large size
ureteral stent after URSL. The irritative symptoms and febrile UTI tended to be less in small stented.

Keywords: Ureteric calculi, Ureteroscopic lithotripsy, Ureteral stent, Stone-free rate