A Comparative Study Between the Usage of Flexible and Navigable Suction Ureteral Access Sheath (FANS) Versus Traditional Access Sheath in RIRS : Randomized Controlled Trial
Phase: NA
Conditions: Stones, Kidney, Ureter Stones
Sponsor: Yosseif elhousseiny ammar ahmed

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Faculty of Medicine, Cairo University Postgraduate 
Research Protocol Template 
(Please read carefully provided guidance documents for a comprehensive understanding and proper 
formulation of your thesis protocol and required forms) 
1. Study
a- Proposed Study Title: A comparative study between the Usage of Flexible and 
Navigable Suction Ureteral Access Sheath (FANS) versus Traditional Access 
sheath in RIRS : Randomized controlled trial .
b- Degree: Master’s degree
c- Date of Registration of MSc or MD: September 2024 
2. Candidate
a.
Name: Youssef Elhousseiny Ammar Ahmed
b.
Occupation: Urology Resident
c.
Affiliation: Urology Department, Faculty of Medicine, Cairo University
d.
Email addresses: yosefelhousseiny@gmail.com
e.
Full mailing address: 269 port-said st. Sayedda zainab, Cairo, Egypt
f.
Phone number: 01226912630
3. Supervisors Contact Information
a.
Principal supervisor:    Name: Prof. Dr. Ahmed Yehia Abdelaziz Mohammed
    Department: Urology Department, Cairo university 
 Phone number: 01229793766 
E-mail addresses: dr_ahmedyehia81@yahoo.com
b.
Other supervisors:
1- Name: Assistant Prof.Dr. Amr Mostafa Sayed Esmail
Department: Urology Department, Cairo University
Phone: 01006803731
Email: Amr154988@gmail.com
2- Name: Lecturer Dr. Mohamed Ahmed Ateya.
Department: Urology Department, Cairo University
Phone: 01003799533
Email: dr.mohamedateya@kasralainy.edu.eg
4. Scientific committee approval
(Was it scientifically approved by the department?) Yes
Date of approval:
Date of document
1/4/2025

                                                                                                           
 
 
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5. Background and Rationale:  
Urinary calculus is a worldwide urological disease, with a prevalence ranging 
from 1% to 13% in different regions (1). Currently, the main therapeutic methods 
beyond conservative treatment for renal calculi include extracorporeal shock wave 
lithotripsy (ESWL) and minimally invasive endoscopic surgical methods, including 
percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS). 
Treatment plans depend on the characteristics of calculi, patient factors, surgeon 
experience and the condition of medical centers (2). 
Technological advancements in RIRS have been numerous in recent years, 
with the introduction of single-use flexible ureteroscopes and higher-power lasers 
being the most notable. High intrarenal pressure (IRP) can lead to pyelovenous 
backflow and infection from transient bacteraemia, particularly during laser lithotripsy. 
Another major concern is the retention of residual fragments (RFs), which are pieces 
that are hidden from view because of the snow-globe effect (3).   
Therefore, in order to facilitate the clearance of RF and enhance the overall 
performance of RIRS, a variety of adjuncts have been developed, including pressure 
sensors to regulate IRP, a direct in-scope vacuum technique to aspirate dust, and 
stone retrieval devices that utilize suction technologies (4).  
These objectives are all designed to achieve the triumvirate of successful 
RIRS: a high stone-free rate (SFR), minimal ancillary interventions, and minimal 
complications—the ultimate goal of all RIRS surgeons (5).  
The ureteral access sheath (UAS) has been used in RIRS to reduce IRP and 
hence infectious complications, as well as to improve drainage, stone clearance, and 
intraoperative vision, thus shortening operative time. However, there still remains 
some debate over the ideal UAS size – too large risks injuring the ureteral mucosa 
and causing ischaemia, while too small defeats its purpose of improving drainage (6). 

                                                                                                           
 
 
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The addition of suction to a traditional UAS resulted in the conception of suction 
ureteral access sheath (SUAS). As demonstrated in clinical studies, the SUAS has 
the potential to reduce intrarenal temperature and pressure, thus reducing infectious 
complications and improving SFR (7, 8). 
Nevertheless, the SUAS continues to exhibit certain constraints (9). If it is 
positioned below the uretero-pelvic junction (UPJ), as is the case with the traditional 
UAS, the application of suction results in the collapse of the proximal ureteral mucosa. 
This reduces the calibre of the narrow UPJ and impedes the aspiration of RF by acting 
as a functional valve to block the opening of the UAS. Despite being positioned across 
the UPJ, it is incapable of overcoming acute angles or reaching distant calyces to 
facilitate the complete aspiration of particulate that has settled in dependent calyces 
(10).  
A flexible-tip SUAS, also known as the flexible and navigable suction UAS 
(FANS), was developed as a natural evolution. This SUAS could be navigated using 
the flexible scope. FANS can be securely maneuvered into individual calyces under 
fluoroscopic guidance to remove fragments and dust more thoroughly and targeted 
through suctioning (11). 
 
6. Objectives:  
This study aims to compare the results between using FANS and conventional 
UAS regarding SFR and postoperative complications. 
 
 
7. Study Design:  
- 
Descriptive: - Survey (cross sectional)   
                   - Qualitative 
 

                                                                                                           
 
 
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- 
Analytic: - Observational: - Case-control study 
                                        - Cross sectional analytic study 
                                        - Cohort (Longitudinal) study 
 
 - Experimental: - Randomized controlled Trial                     Phase: 
                                       - Non-randomized clinical trial 
                                       - Animal study 
                                       - Cellular study 
 
- 
Others:   Please describe:        
            
8. Study Methods 
- 
Population of study:  
Adults ≥14 years old, undergoing RIRS using flexible ureteroscope with renal, 
upper ureteric stones less than 2 cm. 
- 
Study location:  
The study will be conducted in Cairo University Hospitals. 
- 
Inclusion criteria: 
• Age ≥14 years old in patients not known to have stone forming medical 
conditions. 
• Renal stones diameter of ≤2 cm confirmed by CT with all types of 
configurations (branching & non-branching). 
• Non - recurrent cases of previous renal surgeries with normal renal 
anatomy. 
• Patients with non – infected urine analysis. 
 

                                                                                                           
 
 
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- 
Exclusion criteria: 
• Patients with abnormal urinary tract anatomy (such as horseshoe kidney 
or ileal conduit). 
• Pre – stented ureters (with DJs). 
• Patients 
with 
medical 
conditions 
promoting 
stone 
formation 
(hyperparathyroidism – gout). 
• Patients with history of stones on the same side with previous surgical 
intervention. 
• Patients with e-GFR < 90 ml / min. 
• Patients with uncontrolled urinary tract infection. 
• Patients with health or other factors that are absolute contraindications to 
RIRS. 
• Patients who are unable to understand or complete trial documentation. 
- 
Randomization and blindness: 
An online randomization program (http://www.randomizer.org) will be used to 
generate a random list and each patient’s code will be kept in an opaque sealed 
envelope. Patients will be randomly allocated with 1:1 allocation ratio into two groups 
in a parallel manner: 
• Group I (n=40): Patients will undergo FANS. 
• Group II (n=40): Patients will undergo traditional UAS as a control group. 
This study will be open label due to different techniques used. 
- 
Methodology in details: 
• Preoperative: 
- 
Patient demographics. 
- 
History includes personal, medical and surgical  

                                                                                                           
 
 
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- 
Complaint, history of present illness. 
- 
Laboratory Investigations such as: CBC, serum chemistry, coagulation 
profile, urine analysis, urine culture, Hba1C 
- 
Radiological investigations (NCCTUT, plain kub identifying stone 
characteristics (number and location of stones, maximum stone 
diameter, characteristics, and density) Stone density will be measured 
with Hounsfield units on computed tomography (CT) scan. Stone size 
will be assessed as the largest diameter.)  
• Operative: 
▪ FANS technique 
After the successful induction of anesthesia, the lithotomy position will be 
adopted. Ureteroscopy will be used with the aid of a safety guidewire to evaluate the 
condition of the ureter. The serial dilation of the ureter using ureteral dilators up to 14 
Fr . The FANS will be then inserted into the ureter under the guidance of the safety 
guidewire. The FANS tip will be positioned in the renal pelvis or calyces near the 
location of the stone.  
The FANS will be connected to a vacuum device, and the negative pressure 
will be applied. The actual intraoperative negative pressure value will be adjusted by 
the urologist through a pressure adjustment vent as needed. The irrigation volume 
was set using peristaltic pumps. Lithotripsy will be conducted using the holmium: 
yttrium aluminum garnet laser applying the dusting technique of laser lithotripsy. 
During lithotripsy, the FANS will allow us to retrieve most of the fragmented stone 
particles by application of the suction pressure. All cases will be stented using JJ 
stents with the suitable size. 
▪ Traditional UAS technique: 
The method of anesthesia, patient positioning, ureteral dilation, and lithotripsy 
were the same as those used in the FANS group.  

                                                                                                           
 
 
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For the traditional UAS group, the end of the UAS will be positioned underneath 
the ureteropelvic junction (UPJ). The irrigation volume is applied using peristaltic 
pumps. The dusting technique of laser lithotripsy will be applied to the stones. 
 All cases will be stented using JJ stents with the suitable size. 
• Postoperative: 
Postoperative follow-up will be performed for 1 week, 6 weeks, 12 weeks after 
surgery to assess for RF, any post operative complications. 
1 week follow-up will be in the form of a physical examination, bedside 
ultrasound , urine analysis, urine culture. 
The 6-week follow-up will be in the form of NCCTUT, KUB , urine analysis .. 
12 weeks follow-up will be in the form of NCCTUT, urine analysis , urine culture. 
SFR is defined as the absence of a single residual fragments (RF) > 2 mm on 
unenhanced CT scan. 
Postoperative complications will be assessed systematically through: 
- 
History 
- 
Examination (vital instability, fever, tenderness, hematuria, etc) 
- 
Investigations 
(hemoglobin 
drop, 
perinephric 
hematoma 
or 
extravasation, large residuals requiring ancillary procedures). 
 
- 
Intervention: 
 
- 
Diagnostic intervention (please describe):     
 
- 
Therapeutic intervention (please describe): FANS and conventional UAS 
regarding SFR and postoperative complications    
 
- 
No intervention  
 
 

                                                                                                           
 
 
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- 
Does the research involve? 
          Human participants 
          Biological samples/Tissues 
          Identifiable private data/Information     
 
- 
Type of consent of study participants: 
 
          Written consent 
          Oral consent 
          No consent needed (Please justify) 
 
 
- 
Confidentiality of data: 
We will minimize or eliminate the collection of personally identifiable 
information that can be used to distinguish or trace an individual's identity and 
collected data access will be restricted to the participating investigators only . 
 
9. Study outcomes: 
- 
Primary outcome: 
• Stone-free rate (SFR). 
- 
Secondary outcome parameters  
• Operating time. 
• Length of hospital stay. 
• Auxiliary procedures (ESWL – URS or FURS) 

                                                                                                           
 
 
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• Complications (using the clavien – dindo grading system). 
 
10. Sample size  
The sample size calculation was performed using G.power 3.1.9.2 (Universitat 
Kiel, Germany). The sample size was calculated according to the prevalence of initial 
stone-free rate (SFR) was 81.3% with FANS and was 49.4% with traditional UAS 
according to a previous study (9). Based on the following considerations: 0.05 α error 
and 80% power of the study, allocation ration 1:1. Six cases were added to each 
group to overcome dropout. Therefore, 40 patients will be recruited in each group. 
 
11. Statistical analysis  
Statistical analysis will be done by SPSS v26 (IBM Inc., Chicago, IL, USA). 
Shapiro-Wilks test and histograms will be used to evaluate the normality of the 
distribution of data. Quantitative parametric variables will be presented as mean and 
standard deviation (SD) and compared between the two groups utilizing unpaired 
Student’s T- test. Quantitative non-parametric data will be presented as median and 
interquartile range (IQR) and will be analyzed by Mann Whitney-test. Qualitative 
variables will be presented as frequency and percentage (%) and will be analyzed 
utilizing the Chi-square test or Fisher's exact test when appropriate. A two tailed P 
value < 0.05 will be considered statistically significant. 
 
 
         12- Source of funding: (Please include source of funding even if self funding) 
- 
Faculty of Medicine, Cairo University  
- 
Other sources: 
Please specify: None 

                                                                                                           
 
 
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      13- Time plan:  
              
− When to start? The study will be started immediately after thesis registration 
− When expected to finish? Expected time to finish within 6 to 24 months 
according to the availability of cases 
− When to publish? Within 12 months after completion 
  
      14- References:  
1. Lang J, Narendrula A, El-Zawahry A, Sindhwani P and Ekwenna O. Global 
trends in incidence and burden of urolithiasis from 1990 to 2019: An analysis of global 
burden of disease study data. EU Open Science. 2022;35(8):37-46. 
2. Setthawong V, Srisubat A, Potisat S, Lojanapiwat B and Pattanittum P. 
Extracorporeal shock wave lithotripsy (ESWL) versus percutaneous nephrolithotomy 
(PCNL) or retrograde intrarenal surgery (RIRS) for kidney stones. Cochrane 
Database Syst Rev. 2023;8(8):744-852. 
3. Gauhar V, Chai CA, Chew BH, Singh A, Castellani D, Tailly T, et al. RIRS with 
disposable or reusable scopes: does it make a difference? Results from the 
multicenter FLEXOR study. Ther Adv Urol. 2023;15(8):175-628. 
4. Geavlete P, Multescu R, Mares C, Buzescu B, Iordache V and Geavlete B. 
Retrograde intrarenal surgery for lithiasis using suctioning devices: A shift in 
paradigm? J Clin Med. 2024;13(9):841-956. 
5. Abozaid M, Elsherif E, Elserafy F, Abobakr I and Selim M. Preoperative 
prediction of flexible ureteroscopy outcome in the treatment of renal calculi. Afr J Urol. 
2025;31(1):11-98. 
6. Yu Y, Chen Y, Zhou X, Li X, Liu W, Cheng X, et al. Comparison of novel flexible 
and traditional ureteral access sheath in retrograde intrarenal surgery. World J Urol. 
2024;42(1):7-9. 

                                                                                                           
 
 
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7. Gauhar V, Traxer O, Castellani D, Ragoori D, Heng CT, Chew BH, et al. A 
feasibility study on clinical utility, efficacy and limitations of 2 types of flexible and 
navigable suction ureteral access sheaths in retrograde intrarenal surgery for renal 
stones. Urology. 2023;178(5):173-9. 
8. Solano C, Chicaud M, Kutchukian S, Candela L, Corrales M, Panthier F, et al. 
Optimizing outcomes in flexible ureteroscopy: A narrative review of suction 
techniques. J Clin Med. 2023;12(8):541-685. 
9. Zhu W, Liu S, Cao J, Wang H, Liang H, Jiang K, et al. Tip bendable suction 
ureteral access sheath versus traditional sheath in retrograde intrarenal stone 
surgery: an international multicentre, randomized, parallel group, superiority study. 
EClinicalMedicine. 2024;74(5):514-758. 
10. Wang L, Zhou Z, Gao P, Yang Y, Ding Q and Wu Z. Comparison of traditional 
and suctioning ureteral access sheath during retrograde intrarenal surgery in the 
treatment of renal calculi. Langenbecks Arch Surg. 2024;409(1):81. 
11. Ong CSH, Somani BK, Chew BH, Fong KY, Bin Hamri S, Sridharan V, et al. 
Multicentre study comparing outcomes of RIRS using traditional suction ureteral 
access sheath (SUAS) and flexible and navigable suction UAS (FANS). J Clin Urol. 
2024;6(1):205-341. 
 
    
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