Comparison of Lithotomy Versus Lateral Position in Retrograde Intrarenal Surgery for Lower Calyceal Stones Less Than 2 cm

Comparison of Lithotomy Versus Lateral Position in Retrograde Intrarenal Surgery for Lower Calyceal Stones Less Than 2 cm: A Randomized Controlled Trial

Retrograde intrarenal surgery (RIRS) is an established minimally invasive treatment for renal stones, particularly for lower calyceal stones less than 2 cm, offering acceptable stone-free rates with low morbidity.

However, stone clearance in the lower calyx remains technically challenging due to unfavorable anatomy, limited scope deflection, and gravity-dependent fragment retention. Patient positioning during RIRS has been suggested as a modifiable factor that may influence endoscopic access, stone relocation, and surgical ergonomics.

The lithotomy position is conventionally used during RIRS, while the lateral position has been proposed to facilitate stone migration and improve lower calyceal access through gravitational assistance. Existing studies comparing patient positioning during RIRS are limited, with most evidence derived from retrospective analyses or non-randomized designs.

Therefore, this randomized controlled trial aims to compare lithotomy versus lateral positioning during RIRS for lower calyceal stones less than 2 cm in terms of operative and clinical outcomes.

Study Overview

• Status: Not yet recruiting
• Conditions: Renal Calculi
• Intervention / Treatment: Procedure: Lithotomy Position; Procedure: Lateral position

• Study Type: Interventional
• Enrollment (Estimated): 70
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ammar Alorabi; Phone Number: +201067608011; Email: ammar.alorabi95@gmail.com

Study Locations

• Egypt
  • Menoufia
    • Shebin El-Kom, Menoufia, Egypt, 32511
      • Menoufia Faculty of Medicine
      • Contact: Ammar Aziz; Phone Number: +201097991198; Email: ammar.alorabi95@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adults aged ≥18 years.
• Single or multiple lower calyceal renal stones with stone size <2 cm confirmed by NCCT.
• Negative urine culture.
• Presented cases.

Exclusion Criteria:

• Multiple stones involving renal pelvis or other calyces.
• Anatomical anomalies affecting ureteroscope access (horseshoe kidney, malrotation, ureteral strictures).
• Pregnancy.
• Prior ipsilateral renal surgery.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Lithotomy position group; patients of this group undergo RIRS in Lithotomy position	Procedure: Lithotomy Position; Patients undergo RIRS in lithotomy position
Active Comparator: Lateral position group; patients of this group undergo RIRS in lateral position	Procedure: Lateral position; Patients undergo RIRS in lateral position

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Stone Free Rate	Stone-free rate (SFR), defined as no clinically significant residual stones on non-contrast 3-mm-cuts CT, measured as yes or no	1 month

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Operative time	operative time is defined as time between starting the procedure and termination of it measured in minutes	The operative time
Complications	Intra and postoperative complications, defined as complications happens intraoperative and postoperatively, graded by modified clavien-dindo classification	1 month

Collaborators and Investigators

• Sponsor: Menoufia University

Study record dates

Study Major Dates

• Study Start (Estimated): January 1, 2026
• Primary Completion (Estimated): May 1, 2026
• Study Completion (Estimated): June 1, 2026

Study Registration Dates

• First Submitted: December 16, 2025
• First Submitted That Met QC Criteria: December 16, 2025
• First Posted (Actual): December 30, 2025

Study Record Updates

• Last Update Posted (Actual): December 30, 2025
• Last Update Submitted That Met QC Criteria: December 16, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: RIRS; lithotomy position; FURS; lateral position; lower calyx
• Additional Relevant MeSH Terms: Urogenital Diseases; Male Urogenital Diseases; Calculi; Pathological Conditions, Anatomical; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Urolithiasis; Urinary Calculi; Nephrolithiasis; Pathological Conditions, Signs and Symptoms; Kidney Calculi
• Other Study ID Numbers: Patient position in RIRS

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No