Fragmentation Vs Dusting With FANS for Renal Stones Less Than 2cm: A Randomized Controlled Study

June 26, 2026 updated by: Akash Chitrakar, Bir Hospital

Fragmentation Vs Dusting Using TFL With FANS for Renal Stones Less Than 2cm

The use of FANS has changed the operative landscape of RIRS by allowing continuous active suction-assisted clearance of ablated stone material in real time. Use of fragmentation technique in FANS requires high-energy to reduce stone burden into small fragments, followed by active suction of residual fine material. Dusting with FANS, on the other hand, converts the entire stone volume into sub-millimetre particulate that is continuously suctioned away during lasing potentially offering a more streamlined workflow with potentially less energy usage, reduced mechanical stress on the ureteroscope working channel, and fewer scope withdrawals. The combination of TFL dusting with FANS-assisted real-time evacuation may produce stone-free outcomes equivalent or superior to fragmentation, while offering these additional operative efficiencies.

Whether dusting using TFL with FANS is non-inferior or indeed superior to fragmentation using TFL with FANS in terms of stone-free rate at one month has not been evaluated in prospective randomised trial yet. This study aims to answer that specific question in patients with renal stone less than 2 cm.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

Urolithiasis is among the most prevalent urological disorders worldwide, with a lifetime recurrence risk ranging from 30 to 50% in affected individuals. Global Burden of Disease study in 2021 estimated 106 million new incident cases of urolithiasis globally, representing a 47% increase from 1990, driven by population growth, changing dietary patterns, rising rates of metabolic syndrome, and climate-related factors. Regions with tropical and subtropical climates including South Asia bear a disproportionately higher burden, with prevalence estimates of 5-10% compared to 1-5% in temperate regions. Nephrolithiasis is not merely a surgical inconvenience; it imposes significant morbidity through recurrent renal colic, obstructive uropathy, urinary tract infection, and progressive renal dysfunction, with substantial associated healthcare costs.

Retrograde Intra-Renal Surgery (RIRS) has become the preferred minimally invasive modality for the definitive management of most renal calculi endorsed by both the European Association of Urology (EAU) and the American Urological Association (AUA) for stones amenable to endoscopic treatment. It offers the advantage of direct pyelocaliceal access without the morbidity of percutaneous access, with established stone-free rates (SFR) exceeding 90% for stones less than 2 cm in contemporary series.

The operative strategy employed during RIRS specifically, the choice between stone fragmentation and stone dusting remains a subject of active clinical debate, with meaningful implications for operative efficiency, stone-free outcomes, and scope longevity. Fragmentation involves delivering high pulse energy (typically 0.8-1.5 J) at low frequency (5-10 Hz) to reduce calculi into retrievable fragments of less than 4 mm. Dusting employs low pulse energy (0.2-0.5 J) at higher frequency (15-25 Hz) to ablate the stone into sub-millimetre powder particles. In the holmium:YAG (Ho:YAG) laser studies, fragmentation consistently demonstrated superior SFRs. El-Nahas et al. reported a significantly higher SFR with fragmentation compared to dusting (78.6% vs. 58.6%, p=0.035) at 2 months on non-contrast CT, albeit at the cost of a longer operative time (91 vs. 76 minutes, p=0.009). A 2023 systematic review and meta-analysis corroborated these findings, demonstrating that dusting was associated with a lower pooled stone-free rate (OR 0.60; 95% CI 0.41-0.89, p=0.01) and a significantly higher re-treatment rate (OR 2.03; 95% CI 1.31-3.13, p=0.001), though with a shorter operative time and comparable complication profile. These data, however, were generated predominantly with Ho:YAG laser technology and without active suction-assisted clearance, a critical limitation in extrapolating these findings to contemporary practice.

The Thulium Fiber Laser (TFL), introduced into clinical practice in 2018, represents a fundamental technological shift from the Ho:YAG platform. Operating at a wavelength of 1,940 nm, TFL demonstrates a four- to fivefold higher water absorption coefficient, a lower stone ablation threshold, and a more uniform rectangular pulse profile compared to the asymmetrical spike-decay waveform of Ho:YAG. These physical characteristics translate to superior ablation efficiency. TFL achieves fragmentation speeds up to twice and dusting speeds up to ten times faster than Ho:YAG at comparable settings, with significantly less stone retropulsion. Crucially, unlike Ho:YAG where increasing pulse energy generates larger residual fragments, TFL dusting at higher pulse energies does not increase fragment size producing dust particles consistently below 0.254 mm regardless of energy setting, making it inherently better suited to achieving fine, clearable particulate. A systematic review and meta-analysis of TFL-based RIRS reported a pooled SFR of 89.37% (95% CI: 83.93-93.12%), with TFL use independently associated with higher odds of achieving zero-fragment status in multivariable analysis.

The introduction of FANS has fundamentally altered the operative landscape of RIRS by enabling continuous active suction-assisted clearance of ablated stone material in real time. In conventional RIRS without active suction, the inferior stone-free rates historically associated with dusting were largely attributable to inadequate clearance of residual particulate from the pelvicalyceal system. With use of FANS, this limitation is addressed with fragments produced by fragmentation and dust produced by dusting both evacuated under the same negative-pressure suction system. Fragmentation with FANS requires high-energy to reduce stone burden into small fragments, followed by active suction of residual fine material. Dusting with FANS, on the other hand, converts the entire stone volume into sub-millimetre particulate that is continuously suctioned away during lasing potentially offering a more streamlined workflow with potentially less energy usage, reduced mechanical stress on the ureteroscope working channel, and fewer scope withdrawals. Given TFL's inherent superiority in generating fine, consistently small dust particles irrespective of pulse energy; the combination of TFL dusting with FANS-assisted real-time evacuation may produce stone-free outcomes equivalent or superior to fragmentation, while offering these additional operative efficiencies.

Whether dusting using TFL with FANS is non-inferior or indeed superior to fragmentation using TFL with FANS in terms of stone-free rate at one month has not been evaluated in any prospective randomised trial. This study is designed to answer that specific question in patients with renal stone less than 2cm, using a rigorously standardised equipment framework, blinded NCCT KUB-based outcome assessment, and a pre-specified non-inferiority margin of 10%.

Study Type

Interventional

Enrollment (Estimated)

86

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Age ≥18 years
  • Renal stone(s) confirmed on non-contrast CT KUB
  • Total stone less than 2cm
  • Stone amenable to flexible ureterorenoscopy (FURS)
  • FANS advanced beyond Pelvi-Ureteric Junction (PUJ)
  • Able and willing to provide written informed consent
  • Able to comply with follow-up schedule

Exclusion Criteria:

  • Active urinary tract infection (positive urine culture) at time of planned surgery
  • Anatomical anomalies precluding safe FURS (e.g., infundibular stenosis, severe calyceal diverticulum inaccessible to flexible scope)
  • Pregnancy or breastfeeding
  • Prior ipsilateral renal surgery within 3 months of enrollment
  • Concurrent ureteral stone(s) requiring simultaneous treatment
  • Renal anomalies: horseshoe kidney, ectopic kidney
  • Sheathless procedure
  • Unable to comply with follow-up or provide consent
  • Participation in another interventional trial within 30 days

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Fragmentation
0.8-1J, 5-10Hz
Procedure: Fragmentation
Fragmentation involves delivering high pulse energy (typically 0.6-0.8 J) at low frequency (5-10 Hz) to reduce calculi into retrievable fragments of less than 4 mm.
Active Comparator: Dusting
0.6-0.8J, 12-15Hz
Procedure: Dusting
Dusting employs low pulse energy (0.6-0.8 J) at higher frequency (12-15 Hz) to ablate the stone into sub-millimetre powder particles.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Stone free rate
Time Frame: At 1 month after surgery
To determine whether dusting is non-inferior to fragmentation using Thulium Fiber Laser (TFL) with Flexible and Navigable Ureteral Access Sheath (FANS) with respect to stone-free rate (SFR) at 1 month post-procedure in patients with renal stones less than 2cm.
At 1 month after surgery

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Operative time
Time Frame: Intra-operative
To compare total operative time between fragmentation and dusting arms
Intra-operative
Lasing time
Time Frame: Intra-operative
To compare laser activation time between fragmentation and dusting
Intra-operative
Energy consumption
Time Frame: Intra-operative
To compare Energy consumption between two arms
Intra-operative
Ablation speed
Time Frame: Intra-operative
To compare ablation speed between two arms
Intra-operative
Active suction time
Time Frame: Intra-operative
To compare active suction time between fragmentation and dusting
Intra-operative
Number of scope withdrawals
Time Frame: Intra-operative
To compare number of scope withdrawals during active suction between arms
Intra-operative
Re-intervention rates
Time Frame: 3 months
To compare need of auxillary procedures to clear residual fragments between two groups
3 months
Intra-operative Complications
Time Frame: Intra-operatively
To compare incidence of bleeding, PCS injury and ureteral injury between 2 groups
Intra-operatively
Post-operative complications
Time Frame: at end of surgery up to 3 months
To compare incidence of fever, UTI, hematuria, urosepsis and ureteric stricture between two groups
at end of surgery up to 3 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Bir Hospital

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

August 1, 2026

Primary Completion (Estimated)

August 1, 2027

Study Completion (Estimated)

August 7, 2027

Study Registration Dates

First Submitted

June 1, 2026

First Submitted That Met QC Criteria

June 5, 2026

First Posted (Actual)

June 10, 2026

Study Record Updates

Last Update Posted (Actual)

June 30, 2026

Last Update Submitted That Met QC Criteria

June 26, 2026

Last Verified

June 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • BIRH -2026-001

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Subscribe