An interventional study of Flexible and navigable suction ureteral access sheath and Conventional ureteral access sheath in Nephrolithiasis, Kidney Calculi and Retrograde Intrarenal Surgery, sponsored by Ondokuz Mayıs University. Not yet recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-27.
Sponsored by Ondokuz Mayıs University · Not applicable, Interventional, and Treatment
Retrograde intrarenal surgery (RIRS) is a standard minimally invasive treatment for kidney stones up to 20 mm. During the procedure, irrigation fluid raises the pressure inside the kidney and laser energy raises the fluid temperature. High intrarenal pressure has been linked to postoperative pain, fever and infection. Ureteral access sheaths are used to improve fluid outflow, and newer flexible and navigable suction access sheaths (FANS) add active aspiration to keep pressure low and remove stone fragments.
This randomized controlled trial compares three ureteral access strategies in adults undergoing RIRS: a flexible and navigable suction access sheath, a conventional ureteral access sheath, and no access sheath. The main question is whether the access strategy affects pain 6 hours after surgery. The study also compares intrarenal pressure and temperature during surgery, the amount of irrigation fluid used and retained, stone-free status on computed tomography (CT), and complications.
Study design: This is a single-center, prospective, randomized, controlled, three-arm, parallel-group trial conducted at the Department of Urology, Ondokuz Mayis University Faculty of Medicine, Samsun, Turkey.
Participants and randomization: Adults with unilateral kidney stones up to 20 mm who are scheduled for elective RIRS will be randomized in a 1:1:1 ratio to one of three groups: (1) flexible and navigable suction ureteral access sheath, (2) conventional ureteral access sheath, or (3) sheathless flexible ureteroscopy. Allocation will follow a computer-generated block randomization list and will be concealed in sequentially numbered, opaque, sealed envelopes opened after induction of anesthesia. Patients, the investigator recording pain scores, and the radiologist evaluating CT scans will be blinded to group allocation; the surgeon cannot be blinded.
Surgical procedure: All procedures will follow a standardized protocol: sterile preoperative urine culture, antibiotic prophylaxis, general anesthesia, semirigid diagnostic ureteroscopy with passive ureteral dilatation, a flexible ureteroscope with integrated intrarenal pressure sensing, Holmium:YAG laser lithotripsy with standardized settings, standardized saline irrigation, and placement of a double-J stent at the end of the procedure.
Intraoperative measurements: Intrarenal pressure will be recorded continuously from entry into the collecting system until the end of lithotripsy. Mean, maximum and time above 30 mmHg will be calculated. Intrarenal fluid temperature will be recorded with a temperature probe, and mean, maximum and time above 43 degrees Celsius will be calculated. Irrigation volume will be measured by weighing saline bags. Aspirated volume (suction sheath group) and collected outflow volume (all groups, using a fluid-collection drape) will be measured, and retained fluid will be calculated as irrigation volume minus aspirated and collected volumes. Stone volume will be calculated on preoperative non-contrast CT.
Postoperative assessment: All patients will receive a standardized postoperative analgesic regimen, and any rescue analgesia will be recorded. Pain will be assessed with a 0-10 visual analog scale (VAS) at 1, 2, 6 and 24 hours after surgery. Stone-free status will be assessed by low-dose non-contrast CT on postoperative day 1; patients with residual fragments will undergo repeat CT at 3 months. Complications will be graded with the Clavien-Dindo classification, and ureteral wall injury will be graded with the PULS classification at the end of the procedure.
Sample size and analysis: A sample of 43 patients per group (129 in total) was calculated to detect a 1.5-point difference in 6-hour VAS score between groups (standard deviation 2.0, alpha 0.0167 with Bonferroni correction for three pairwise comparisons, 80% power, 10% dropout). Groups will be compared using ANOVA or Kruskal-Wallis tests for continuous variables and chi-square or Fisher exact tests for categorical variables. Repeated VAS measurements will be analyzed with a linear mixed model, and the relationship between intrarenal pressure and postoperative pain will be assessed with correlation and multiple linear regression analyses. Analyses will be performed on an intention-to-treat basis.
468 studies on the registry are indexed under Nephrolithiasis; 108 are open to participants now.
This study's planned enrollment of 129 is above the median of 90 across 365 interventional studies indexed under Nephrolithiasis.
Browse Nephrolithiasis studies →Ondokuz Mayıs University is the lead sponsor of 275 studies on the registry; 68 are open to participants now.
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Exclusion Criteria:
A commercially available flexible and navigable suction ureteral access sheath with a flexible distal tip, placed over a guidewire under fluoroscopic guidance. Continuous aspiration of irrigation fluid and stone fragments is applied through the sheath at a standardized suction pressure during laser lithotripsy.
Device: Flexible and navigable suction ureteral access sheath · Procedure: Retrograde intrarenal surgery with laser lithotripsy
A commercially available standard (non-suction) ureteral access sheath, placed over a guidewire under fluoroscopic guidance with its tip at the level of the ureteropelvic junction. Irrigation fluid drains passively through the sheath around the ureteroscope.
Device: Conventional ureteral access sheath · Procedure: Retrograde intrarenal surgery with laser lithotripsy
Patients undergo retrograde intrarenal surgery without a ureteral access sheath. After diagnostic semirigid ureteroscopy and passive ureteral dilatation, the flexible ureteroscope is advanced directly over a guidewire into the collecting system. Irrigation fluid drains passively alongside the ureteroscope. All other surgical steps, irrigation settings, laser settings and postoperative care are identical to the other arms.
Procedure: Sheathless flexible ureteroscopy · Procedure: Retrograde intrarenal surgery with laser lithotripsy
A \[10/12\] Fr flexible and navigable suction ureteral access sheath (\[brand/model\]) with a flexible distal tip that follows the ureteroscope into the renal calyces. The side port is connected to a suction unit set at \[x\] mmHg, providing continuous aspiration of irrigation fluid and stone fragments during lithotripsy.
A \[10/12\] Fr standard (non-suction) ureteral access sheath (\[brand/model\]) placed with its tip at the level of the ureteropelvic junction. Irrigation fluid drains passively through the sheath around the ureteroscope.
Flexible ureteroscopy performed without a ureteral access sheath. The flexible ureteroscope is advanced over a guidewire after diagnostic semirigid ureteroscopy and passive ureteral dilatation.
Standardized retrograde intrarenal surgery under general anesthesia using a flexible ureteroscope with integrated intrarenal pressure sensing and Holmium:YAG laser lithotripsy with standardized settings. Intrarenal pressure and fluid temperature are recorded continuously, irrigation and outflow volumes are measured, and a double-J stent is placed at the end of the procedure in all patients.
Postoperative pain score
Pain intensity measured with a 0-10 visual analog scale (VAS); 0 = no pain, 10 = worst imaginable pain.
Time frame: 6 hours after surgery
Postoperative pain scores
Pain intensity measured with a 0-10 visual analog scale (VAS); 0 = no pain, 10 = worst imaginable pain.
Time frame: 1, 2 and 24 hours after surgery
Number of rescue analgesic doses
Number of rescue analgesic doses administered in addition to the standardized postoperative analgesic regimen.
Time frame: First 24 hours after surgery
Mean intrarenal pressure
Mean intrarenal pressure (mmHg) recorded continuously by the pressure-sensing flexible ureteroscope.
Time frame: Intraoperative
Maximum intrarenal pressure
Maximum intrarenal pressure (mmHg) recorded during the procedure.
Time frame: Intraoperative
Time with intrarenal pressure above 30 mmHg
Total time (seconds) during which intrarenal pressure exceeds 30 mmHg.
Time frame: Intraoperative
Mean intrarenal fluid temperature
Mean intrarenal fluid temperature (degrees Celsius) recorded continuously with a temperature probe.
Time frame: Intraoperative
Maximum intrarenal fluid temperature
Maximum intrarenal fluid temperature (degrees Celsius) recorded during the procedure.
Time frame: Intraoperative
Time with intrarenal fluid temperature above 43 degrees Celsius
Total time (seconds) during which intrarenal fluid temperature exceeds 43 degrees Celsius.
Time frame: Intraoperative
Irrigation fluid volume
Total volume of irrigation fluid used (mL), measured by weighing saline bags.
Time frame: Intraoperative
Aspirated fluid volume
Volume of fluid aspirated through the suction sheath (mL); applicable to the FANS group only.
Time frame: Intraoperative
Collected outflow volume
Volume of irrigation fluid collected in the fluid-collection drape (mL).
Time frame: Intraoperative
Retained irrigation fluid volume
Irrigation volume minus aspirated and collected volumes (mL).
Time frame: Intraoperative
Stone-free rate
Percentage of participants without residual stone fragments on non-contrast computed tomography.
Time frame: Up to 3 months after surgery
Postoperative fever
Number of participants with body temperature of 38 degrees Celsius or higher.
Time frame: Up to 30 days after surgery
Infectious complications
Number of participants who develop systemic inflammatory response syndrome (SIRS) or urosepsis.
Time frame: Up to 30 days after surgery
Postoperative complications
Number of participants with any postoperative complication graded according to the Clavien-Dindo classification.
Time frame: Up to 30 days after surgery
Ureteral wall injury
Grade of ureteral wall injury according to the Post-Ureteroscopic Lesion Scale (PULS), assessed endoscopically.
Time frame: At the end of the procedure
Operative time
Time from insertion of the semirigid ureteroscope to placement of the double-J stent (minutes).
Time frame: Perioperative/Periprocedural
Length of hospital stay
Time from surgery to hospital discharge (days).
Time frame: Up to 7 days after surgery
Plan to share: No
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Start is estimated for Nov 2026; primary completion for Jul 2027, 8 months later.
Of 177 non-industry interventional studies with no phase under Nephrolithiasis, half reached primary completion within 25 months of starting (the median), counting those still running; a quarter within 12 and three quarters within 40. This study's planned 8 months is below that.
Counting every sponsor, half of 185 studies reached it within 24 months; a quarter within 12 and three quarters within 40.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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