Kidney stone disease is a common condition, and retrograde intrarenal surgery (RIRS) is a minimally invasive procedure frequently used to remove kidney stones. During RIRS, pressure inside the kidney can increase, which may contribute to temporary kidney injury. New aspiration-enabled access sheath systems have been developed to better control this pressure by continuously removing irrigation fluid during surgery. This study will compare aspiration and conventional access sheath systems to determine whether improved pressure control reduces early kidney injury. Blood and urine biomarkers (IL-18 and L-FABP), which can detect kidney damage earlier than standard kidney function tests, will be measured before and after surgery. The results may help identify surgical techniques that better protect kidney function and improve the safety of kidney stone treatment for patients.

Urinary system stone disease is a common condition in urological practice, and with advances in minimally invasive surgical techniques, retrograde intrarenal surgery (RIRS) has become a widely preferred method, particularly for treating small and medium-sized kidney stones, owing to its high stone-free rates and low morbidity. The ureteral access sheath (UAS), routinely used during RIRS, offers advantages such as facilitating repeated entry and exit, shortening operation time, optimizing irrigation flow, and reducing intrarenal pressure. However, controlling intrarenal pressure is critical not only for surgical comfort but also for renal physiology and patient safety. Increased intrarenal pressure can lead to pyelovenous, pyelolymphatic, and pyelotubular regurgitation, increasing the risk of bacterial translocation, sepsis, and renal parenchymal damage. In particular, the damage that high intrarenal pressure can cause to the renal parenchyma and the resulting acute kidney injury (AKI) are of significant importance in critically ill patients who are clinically at risk of renal failure. Recent developments of aspiration-enabled intrarenal electroconvulsive (IOC) systems aim to more effectively and continuously control intrarenal pressure by providing active fluid drainage. Theoretical advantages of these systems include lower intrarenal pressure levels, improved visualization quality, and potentially lower complication rates. However, the effects of these systems on renal function have been evaluated in a limited number of studies in the current literature, and their effects, particularly on subclinical renal damage, have not been clearly established.

Acute renal injury (AKI) is a rare but clinically significant complication following RIRS, and it is often undetectable early using conventional biochemical parameters (e.g., serum creatinine). Therefore, the use of early and sensitive biomarkers is becoming increasingly important. In this context, Interleukin-18 and Liver-type fatty acid binding protein (L-FABP) stand out as promising biomarkers that can reflect early renal tubular damage and predict the development of AKI. The aim of this study is to comparatively evaluate the effects of aspiration and non-aspiration ureteral access sheath systems used during RIRS on postoperative acute renal injury, based on changes in IL-18 and L-FABP levels. Furthermore, by revealing the relationship between intrarenal pressure control and biochemical injury markers, the study aims to provide stronger evidence for the potential clinical benefits of aspiration systems.

Inclusion Criteria:

• Being 18 years of age or older
• Having a planned RIRS operation
• Providing written informed consent

Exclusion Criteria:

• Patients who do not give consent
• Patients who will undergo combined surgery
• Patients who have previously undergone endoscopic stone surgery
• Being under 18 years of age
• Patients with chronic kidney failure
• Patients with kidney malformations
• Patients with a solitary kidney
• Patients using nephrotoxic drugs