The study aims to compare renal oxygenation levels in retrograde intrarenal surgery (RIRS) and ureteroscopy (URS) procedures with a control group. Additionally, it seeks to determine if there is a connection between postoperative infection parameters and intraoperative renal oxygenation measurements.

The study will involve ASA class I-III pediatric patients aged 1-18 undergoing RIRS, URS, and hypospadias surgery under general anesthesia. Patients will be divided into three groups: Group R (RIRS), Group U (URS), and Group H (Hypospadias/Control). Data collection will include patient height and weight. In Groups R and U, pre- and postoperative measurements such as hemoglobin, hematocrit, leukocyte count, BUN, serum creatinine, procalcitonin, interleukin-6, and CRP values will be recorded.

All three groups will undergo NIRS monitoring alongside routine ASA monitoring. Renal NIRS probes will be positioned using ultrasonography, and the average of three measurements will determine the regional oxygen saturation index (rSO2) as the initial value. NIRS, pulse oximetry, and hemodynamic data will be recorded every 5 minutes until recovery from anesthesia just prior to induction. A decrease of 20% or more than 20% when comparing NIRS values during follow-up with the baseline will be considered significant. The study will also document anesthesia and surgery times, as well as postoperative fever and the amount of irrigation fluid used in Groups R and U.

Inclusion Criteria:

• 1-18 years ASA I-III class,
• Patients who will undergo RIRS, URS and Hypospadias surgeries under standard general anesthesia.
• Patients whose informed consent form is approved by their parents will be included in the study.

Exclusion Criteria:

• Exclusio criteria were the history of renal failure, renal tumors, infection of the perirenal region; receiving colloid or blood transfusion, having abscess, body mass index (BMI) not in the normal limits (≤3% or ≥97%)
• Patients whose parents do not approve the informed consent form will not be included in the study.

Due to the patient population of the hypospadias operation, Group H will consist of only male patients.

ASA I-III class between the ages of 1-18, patients who will undergo RIRS and URS surgery under standard general anesthesia, as well as patients who will undergo hypospadias surgery (without a history of stones or kidney problems).