Ureteroscopic laser lithotripsy (URSLL) is one of the mainstays in the surgical management of upper urinary tract stone disease.¹ Since its advent in the 1980s, the procedure has seen a myriad of technological improvements ranging from the introduction of flexible, fiber optic ureteroscopes to state-of-the-art lasers with pulse modulation technology. Indeed, in the never-ending quest to increase stone-free rates (SFRs) and decrease operative times, the endourological repertoire of gadgetry has ballooned to such a degree that it is difficult to keep track of it all. While technological advancements are in large part responsible for the success of modern medicine, they often lead us to overlook the simplest tool in the urologist’s armamentarium: gravity. Multiple studies have suggested that in the ureter and kidney alike, stone location is a significant predictor of SFR during URSLL.^2,3 Specifically, stones in lower pole calyces are associated with the lowest SFR of any location in the upper urinary tract.^2,3 Simply put, gravity allows surgeons to move stones from unfavorable locations into favorable ones. Herein, we provide an overview of positioning techniques which maximize the benefit of gravity.

The concept of gravitational stone repositioning has been in our field for decades. Postural inversion therapy was introduced soon after the arrival of extracorporeal shock wave lithotripsy for lower pole stones, and studies have suggested improvements in SFRs.⁴ This slowly translated over to the realm of URSLL, when Herrell and Buchanan reported a small series of patients who underwent URSLL in the flank position, with the stone-bearing kidney up.⁵ They found that both whole stones and fragments preferentially migrated medially toward the renal pelvis, facilitating both lithotripsy and extraction. More recently, our group performed a randomized trial comparing flexible URSLL for renal stones in either the standard flat dorsal lithotomy position or the T-tilt position.⁶ The T-tilt position involves rotation of the operating table into a 15° Trendelenburg position (head below pelvis) and simultaneous 15° lateral rotation (ie airplane) away from the surgical side kidney (Figs. 1 and 2). This position harnesses gravity to pull stones and stone fragments medially and superiorly, favoring the upper pole and renal pelvis, where ergonomics of flexible URSLL are significantly improved. Overall, patients in the T-tilt group had a significantly higher SFR (92.1% vs 76.7%). This difference was even more pronounced for patients with isolated lower pole stones (95.6% vs 68.2%). Along the same lines, 2 studies have also demonstrated a benefit to displacing proximal ureteral stones into the kidney.^7,8 Both randomized trials revealed that placing patients with proximal ureteral stones in the Trendelenburg position during URSLL resulted in preferential migration of stone fragments into the renal pelvis and upper pole, resulting in improvements in SFR and operative time, and less need for conversion from a semirigid to a flexible ureteroscope.

	Figure 1. An actual patient in the T-tilt position (15° Trendelenburg, 15° airplane with stone side up).
	Figure 2. Radiographic and anatomical representation of a lower pole renal stone in the flat dorsal lithotomy position (A) and in the T-tilt position (B).

Despite the convincing evidence that patient positioning can enhance URSLL outcomes, we must acknowledge that it comes with certain risks and drawbacks. Given the physiological effects associated with Trendelenburg positioning, we avoid the T-tilt strategy in patients with severe lung disease, congestive heart failure or morbid obesity. Another drawback is that the operating room must be equipped with a table with inversion and airplane functions. While inversion is a nearly universal feature in the operating room, we are aware that many cystoscopy-dedicated tables do not allow for lateral rotation. In such cases, lateral tilt can perhaps be achieved by placing patients in the Valdivia-Galdakao position, as would be used for supine endoscopic combined intrarenal surgery. Bolsters can be placed underneath the torso to elevate the surgical side kidney prior to initiating the procedure. The Trendelenburg position can then be assumed once the procedure has begun. In our experience, the slight change in angle of the patient’s pelvis in relation to the floor does not alter the ergonomics of the procedure, particularly when using a flexible ureteroscope. Finally, although comparative data are lacking for URSLL performed in the full flank position, we posit that it could enhance surgical outcomes to a similar degree as T-tilt. However, we have not employed full flank positioning in our practice for several reasons. First, it requires more time and coordination with anesthesia in patient positioning. Second, the position is essentially permanent, allowing for little to no flexibility once the patient has been draped. This accentuates the adaptability of the T-tilt position, which can be changed and fine-tuned on the fly in mere seconds. Lastly, the full flank position severely restricts transurethral access with rigid endoscopic instruments, which may make certain cases more challenging.

Overshadowed by the glamour of ever-improving surgical technology, we often forget that simple interventions can be equally powerful in improving patient outcomes. In URSLL, using gravity to our advantage is one of those simple solutions. Intraoperative table tilt is cost-free, requires no additional operative time or training for staff, and poses minimal added risk to appropriately selected patients. For these reasons, we routinely place our patients in the T-tilt position during URSLL and encourage other urologists to experiment with patient positioning in the endoscopic management of urinary stone disease.