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Randomized Controlled Trial
. 2025 Oct 31;43(1):655.
doi: 10.1007/s00345-025-06011-7.

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

T Amiel  1 , A Neisius  2 , C Netsch  3 , A Secker  4 , C Fisang  5 , I Grunwald  6 , L Lunger #  7 , M Straub #  7
Affiliations
Randomized Controlled Trial

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

T Amiel et al. World J Urol. .

Abstract

Purpose: Achieving 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® was developed to embed and extract even the smallest fragments with conventional baskets. This study aimed to evaluate the safety and feasibility-defined as the ability to extract fragments < 1 mm-of stone extraction during flexible ureterorenoscopy with or without the hydrogel method.

Materials and methods: This 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.

Results: Of 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.

Conclusions: The 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.

Keywords: Flexible ureterenoscopy; Hydrogel method; Stone dusting; Stone free rate; Urolithiasis.

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Conflict of interest statement

Declarations. Conflict of interest: Amiel, Straub, Netsch, Neisius and Grunwald reported having consulting agreements with Farco-Pharma. Ethical approval: This study was performed in line with the principles of the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the local ethical committee. This study was registered with www.bfarm.de (DRKS00030532) in September of 2021.

Figures

Fig. 1
Fig. 1
Application of mediNiK®, A application of K1, B application of K2, C extraction of the hydrogel clot, D extracted hydrogel clot embedding stone fragments
Fig. 2
Fig. 2
CONSORT FlowChart. SES safety evaluation set, FAS full analysis set
Fig. 3
Fig. 3
Bar chart of size of extracted kidney stones per treatment arm, n number of removed stones/fragments. % percentage based on the total number of extracted stones per treatment arm. fURS flexible ureteroscopy, MN mediNiK®
See this image and copyright information in PMC

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