Stone extraction during flexible ureterorenoscopy with or without the hydrogel method: a randomized, multicenter safety and feasibility study.

purposeAchieving the highest possible stone-free rate is the primary goal of kidney stone surgery, yet standard flexible ureterorenoscopy often leaves small residual fragments that predispose to recurrence. The hydrogel method using mediNiK MATERIALS AND

methodsThis prospective, randomized, multicenter proof-of-concept trial included patients > 18 years with kidney stones > 8 mm and no anatomical abnormalities. Patients were randomized to flexible ureterorenoscopy + hydrogel (Group 1) or flexible ureterorenoscopy (Group 2) alone. After laser lithotripsy, fragments were retrieved either embedded in hydrogel or individually, and categorized by size (< 0.5 mm, 0.5-1.0 mm, > 1.0 mm). Explorative statistical analyses included Mann-Whitney U, Student's t-test, and Chi-square test. Adverse events were monitored intraoperatively and during a 6-week follow-up.

resultsOf 65 screened patients, 40 were analysed (Group 1: n = 23; Group 2: n = 17). The hydrogel method significantly retrieved more fragments < 1 mm (1716 vs. 209) and > 1 mm (310 vs. 118). On a per-patient level, more < 1 mm fragments were removed in Group 1 (median 7 [IQR 21] vs. 0 [2], p < 0.003). Surgery duration was longer in Group 1 (80 [28] vs. 62 [20] minutes, p = 0.02). No serious adverse events were reported.

conclusionsThe hydrogel method was a safe and feasible addition to fURS, allowing improved retrieval of even the smallest fragments without added risk. The main limitations are the small sample size and absence of long-term stone-free and recurrence data, underscoring the need for larger confirmatory studies.