Clinical Research Directory

Renal Structural and Functional Alterations Following Repeated Ureteroscopic Procedures: An Exploratory Multimodal Imaging Study

Introduction and objectives Saline irrigation and instrumentation during Retrograde Intrarenal Surgery (RIRS) causes elevation of intrarenal pressure (IRP) inducing intrarenal backflow (IRB). In an experimental study from 2025 Hinojosa-Gonzalez et al. demonstrated an association between elevated IRP and increased risk of bacteremia. The potential of elevated IRP and IRB to breach physiological barriers and facilitate systemic translocation of renal pelvic contents warrants investigation into their effects on parenchymal integrity and function. Using contrast-enhanced MRI in a porcine model, Lildal et al. (2023) demonstrated segmental IRB with sharply demarcated areas of contrast distribution, predominantly at the renal poles. The preferential involvement of renal poles resembles the distribution of renal scarring observed in reflux nephropathy, raising the hypothesis that repeated pressure-related exposure may contribute to localized parenchymal alterations. However, whether repeated ureteroscopic procedures are associated with similar persistent regional changes in renal structure and function remains unclear. We therefore initiated an exploratory clinical study assessing renal structure and function following multiple ureteroscopic procedures using multiparametric MRI, DMSA scintigraphy and ultrasound elastography. Materials and methods This exploratory cross-sectional case-control study aims to enroll 10 patients with repeated unilateral ureteroscopic procedures and 10 healthy controls. Eligible patients must have undergone ≥3 ipsilateral procedures (RIRS/URS/URSL) and ≤1 contralateral procedure. Major exclusions include solitary kidney, metabolic or structural renal disorders compromising MRI analysis, chronic UTI, previous multiple PCNL procedures, and MRI contraindications. All participants undergo serum creatinine measurement and multiparametric renal MRI (1.5T Philips Ingenia), including T1 mapping, heavily T2-weighted 3D imaging, diffusion-weighted imaging, T2\* imaging, and renal arterial flow assessment. Renal scintigraphy is performed using ⁹⁹ᵐTc-DMSA, with planar imaging for quantification of split renal function and SPECT for evaluation of cortical scarring. Bilateral renal shear-wave elastography (Mindray Resona I9 ultrasound system) is conducted to quantify regional parenchymal stiffness in five predefined regions per kidney. Planned analyses will compare regional imaging parameters between patients and controls and between ipsilateral and contralateral kidneys, accounting for within-subject correlation. Segmental imaging parameters will be compared between groups and kidneys using linear mixed-effects models accounting for repeated measurements within subjects.

Ureteral Access Strategies in Retrograde Intrarenal Surgery

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.