Flexible Ureteroscopy With a Flexible and Navigable Suction Ureteral Access Sheath Versus Mini-Percutaneous Nephrolithotomy for 1-2 cm Lower Pole Kidney Stones (FLAME)

Guangzhou Medical University

Status: Enrolling

Conditions: Kidney Stones

Treatments: Procedure: Flexible ureteroscopy with FANS; Procedure: Mini-percutaneous nephrolithotomy (mini-PCNL)

Study type: Interventional

Funder types: Other; NETWORK

Identifiers

NCT07159035

ES-2025-181

Details and patient eligibility

About

This study, known as the FLAME Trial (Flexible ureteroscopy for Lower pole stones And Mini-pErcutaneous nephrolithotomy), is an international, multicenter, randomized, non-inferiority trial. It aims to compare the effectiveness and safety of flexible ureteroscopy using a flexible and navigable suction ureteral access sheath (FANS) versus mini-percutaneous nephrolithotomy (mini-PCNL) in the treatment of 1-2 cm lower pole kidney stones.

A total of 640 eligible adult patients will be enrolled across 20 high-volume urology centers in China, Russia, Turkey, and India. Participants will be randomly assigned to undergo either FANS-assisted flexible ureteroscopy or mini-PCNL. The primary outcome is the immediate stone-free rate (SFR) assessed by non-contrast CT within 72 hours after surgery. Secondary outcomes include SFR at 1 month, operative time, pain score, length of hospital stay, complication rates, and changes in health-related quality of life.

The goal of this trial is to determine whether the less invasive FANS-assisted approach is non-inferior to mini-PCNL in terms of efficacy, while potentially offering advantages in postoperative recovery and safety.

Full description

The FLAME Trial (Flexible ureteroscopy for Lower pole stones And Mini-pErcutaneous nephrolithotomy) is an international, multicenter, prospective, randomized, controlled, non-inferiority study that aims to evaluate the safety and efficacy of flexible ureteroscopy assisted by a Flexible and Navigable Suction Ureteral Access Sheath (FANS) compared with mini-percutaneous nephrolithotomy (mini-PCNL) in the treatment of 1-2 cm lower pole renal stones.

This trial will enroll 640 patients from 20 urology centers with substantial experience in endoscopic stone surgery, including hospitals in China, Russia, Turkey, and India. Eligible participants will be randomly assigned in a 1:1 ratio to either the FANS-assisted flexible ureteroscopy group or the mini-PCNL group. All patients will undergo preoperative imaging, intraoperative standardization, and postoperative follow-up according to the study protocol.

The primary endpoint is the stone-free rate (SFR) within 72 hours postoperatively, evaluated by non-contrast-enhanced computed tomography (NCCT). Secondary endpoints include SFR at 1 month, operative time, length of hospital stay, postoperative pain (measured by VAS score), complication rates (graded by Clavien-Dindo classification), changes in renal function, and health-related quality of life (HRQoL).

The FANS, developed to improve irrigation control and active stone fragment suction during flexible ureteroscopy, may provide better visualization, reduce intrarenal pressure, and shorten operative time. By directly comparing FANS-assisted fURS with mini-PCNL, the trial seeks to determine whether a less invasive method can achieve comparable outcomes in terms of stone clearance and complication rates.

Enrollment: 640 estimated patients

Sex: All

Ages: 18 to 75 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

1. Adults aged 18-75 years;
2. American Society of Anesthesiology (ASA) score 1-3;
3. Lower pole renal stones-single or multiple-with a maximal diameter of 1-2 cm confirmed by CT;
4. Ability to provide written informed consent and adhere to trial requirements.

Exclusion criteria

1. Significant urinary tract anatomical anomalies (e.g. horseshoe kidney, ileal conduit);

2. Stones located within a calyceal diverticulum;

3. History of open nephrolithotomy or ureterolithomy (due to resultant intrarenal anatomical distortion);

4. Absolute contraindications to either FANS-f-URS or mini-PCNL, including:

   • Uncorrectable coagulopathy;
   • Active, uncontrolled urinary tract infection;
   • Severe cardiopulmonary disease precluding safe general anesthesia (e.g. decompensated heart failure, refractory COPD);
   • Pregnancy;
   • Inability to tolerate lithotomy or prone positioning;

5. Inability to understand or complete trial documentation.

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Double Blind

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640 participants in 2 patient groups

FANS-fURS Group

Experimental group

Description:

Patients assigned to this group will undergo flexible ureteroscopy with FANS (Flexible endoscopy-Assisted Negative-pressure Suction Sheath). The FANS facilitates direct stone visualization, fragmentation, suction, and removal under controlled pressure conditions.

Treatment:

Procedure: Flexible ureteroscopy with FANS

mini-PCNL Group

Active Comparator group

Description:

Patients in this group will receive mini-percutaneous nephrolithotomy (mini-PCNL) via less than 20 Fr percutaneous tracts.

Treatment:

Procedure: Mini-percutaneous nephrolithotomy (mini-PCNL)