Ureteroscopic management of proximal ureteral stones presents technical challenges including stone retropulsion, prolonged operative time, and conversion to intrarenal treatment. Reverse Trendelenburg positioning has been shown to reduce proximal stone migration and operative time in ureteral stones, while the T-tilt position improves intrarenal stone clearance. The optimal strategy for proximal ureteral stones (treating stones in situ using reverse Trendelenburg versus pushing stones into the kidney followed by intrarenal treatment in T-tilt) remains unknown.

This randomized controlled trial compares these two strategies, with primary focus on operative time as a measure of procedural efficiency.

A total of 54 patients (27 per arm) will be enrolled at Mount Sinai West.

Ureteroscopy has become a primary modality for the management of ureteral and renal calculi due to its high efficacy, minimally invasive nature, and favorable safety profile. Despite advances in flexible ureteroscopy, laser lithotripsy, and access technologies, proximal ureteral stones remain technically challenging, largely due to their tendency to migrate retrograde into the kidney, leading to prolonged operative time, increased need for flexible ureteroscopy, and lower procedural efficiency.

Stone retropulsion is influenced by laser energy, irrigation flow, ureteral anatomy, and gravitational forces. Several mechanical and laser-based strategies have been explored to mitigate migration, though results have been variable. Patient positioning represents a simple and cost-neutral intervention that may alter stone behavior intraoperatively without requiring additional devices.

Reverse Trendelenburg positioning has recently been shown to reduce proximal stone migration and improve operative efficiency during ureteroscopic treatment of ureteral stones. In a randomized controlled trial, patients positioned in reverse Trendelenburg experienced lower rates of retropulsion, reduced need for conversion to flexible ureteroscopy, and shorter operative times compared with standard positioning. However, this study included stones across multiple ureteral segments and did not focus specifically on proximal ureteral stones, which may have distinct anatomical and migration characteristics.

Conversely, T-tilt positioning has been investigated in the context of intrarenal stone treatment. Prior randomized evidence demonstrated that T-tilt positioning during retrograde intrarenal surgery resulted in higher stone-free rates, likely due to improved gravitational alignment of calyces and enhanced fragment clearance. These findings suggest that positioning may also optimize intrarenal lithotripsy efficiency once stones migrate into the kidney.

For proximal ureteral stones, two competing operative strategies are commonly used in clinical practice: (1) in situ ureteral treatment with efforts to prevent migration, potentially optimized by reverse Trendelenburg positioning, or (2) intentional pushback of the stone into the kidney followed by intrarenal lithotripsy under positioning conditions favorable for fragment clearance, such as T-tilt.

The decision to use one strategy over another is based on surgeon preference. Currently, there are no guidelines or standards favoring either approach. To date, no randomized study has directly compared these two positioning-based strategies for proximal ureteral stones. Given that operative time is strongly associated with anesthesia exposure, procedural cost, complication risk, and resource utilization, it represents a clinically meaningful and objective primary endpoint to evaluate procedural efficiency between approaches.

This study seeks to address an important gap in endourologic practice by determining the optimal positioning strategy for proximal ureteral stone management, with the goal of improving operative efficiency, reducing procedural burden, and informing evidence-based surgical decision-making.

Inclusion criteria:

• Adults aged 18 years and older.
• Diagnosed with kidney stones and scheduled for fURS.
• Stone burden > 1 cm and/or multiple stones will be eligible.
• Able and willing to provide informed consent.

Exclusion criteria:

• Pregnant persons as determined by pre-operative urine pregnancy test (standard of care at the institution)
• Untreated UTI
• Patients with urinary anomalies (e.g., urinary diversion, ureteral reconstruction, horseshoe kidney)
• Single stone < 1 cm

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