Effect of Negative Pressure Suction on Fluid Absorption and Infection in Flexible Ureteroscopy

The goal of this observational study is to learn about the effects of using negative pressure suction during retrograde intrarenal surgery (RIRS) in patients aged 18 and older with kidney stones. The main questions it aims to answer are: 1. Does using negative pressure suction during surgery affect the amount of irrigation fluid absorbed by the patient's body? 2. Does using negative pressure suction reduce the risk of postoperative infections, such as fever, systemic inflammatory response syndrome (SIRS), and urosepsis? Researchers will compare patients who undergo surgery with a negative pressure suction sheath to patients who undergo surgery with a standard sheath (without suction) to see if the suction technology reduces fluid absorption and lowers the risk of postoperative complications. Participants will undergo their scheduled kidney stone surgery as part of their regular medical care. Researchers will collect their routine clinical data from the hospital system, including: 1. Preoperative test results (such as CT scans, ultrasounds, and urine tests). 2. Intraoperative data (such as surgery duration and the exact amount of fluid absorbed, measured by a monitoring device). 3. Postoperative recovery data (such as body temperature, pain levels, hospital stay length, and any signs of infection).