This prospective observational study aims to evaluate renal perfusion in adult patients undergoing elective minimally invasive abdominal surgery. Renal perfusion will be assessed using two non-invasive monitoring techniques: Doppler ultrasonography-derived Renal Resistive Index (RRI) and Near-Infrared Spectroscopy (NIRS)-derived renal regional oxygen saturation (rSO₂).

Measurements will be obtained at predefined perioperative time points, including after induction of anesthesia, during pneumoperitoneum, before extubation, and during the early postoperative period. Perioperative changes in renal perfusion parameters will be analyzed and correlated with clinical variables such as intra-abdominal pressure, pneumoperitoneum duration, hemodynamic parameters, fluid administration, urine output, and postoperative renal function.

The study also aims to investigate the relationship between intraoperative renal perfusion changes and the development of postoperative acute kidney injury. The findings may contribute to improved perioperative monitoring and optimization of renal perfusion during minimally invasive abdominal surgery.

Minimally invasive abdominal surgery has become increasingly common because of reduced surgical trauma, faster recovery, and lower postoperative morbidity compared with conventional open surgery. However, laparoscopic procedures require the creation of pneumoperitoneum, which may increase intra-abdominal pressure and adversely affect renal blood flow, renal oxygen delivery, and kidney function.

Renal hypoperfusion during surgery may contribute to postoperative renal dysfunction and acute kidney injury (AKI). Traditional indicators of renal injury, such as serum creatinine and urine output, often fail to detect early changes in renal perfusion. Therefore, reliable non-invasive methods for real-time assessment of renal perfusion are needed.

Doppler ultrasonography-derived Renal Resistive Index (RRI) and Near-Infrared Spectroscopy (NIRS)-derived regional renal oxygen saturation (rSO₂) are promising techniques for evaluating renal perfusion and oxygenation. Both methods provide non-invasive, bedside assessment and may allow early detection of perfusion abnormalities before conventional markers become abnormal.

This prospective single-center observational study will evaluate perioperative renal perfusion in adult patients undergoing elective minimally invasive abdominal surgery. Renal perfusion measurements will be obtained using Doppler ultrasonography and NIRS at predefined perioperative time points, including after induction of anesthesia, during pneumoperitoneum, before extubation, and during the early postoperative period.

Demographic characteristics, comorbidities, baseline renal function, intraoperative hemodynamic variables, pneumoperitoneum duration and pressure, fluid administration, urine output, blood loss, ventilatory parameters, and postoperative renal function will be recorded. Associations between perioperative renal perfusion parameters and postoperative renal outcomes, including acute kidney injury, will be investigated.

The findings of this study may improve understanding of perioperative renal perfusion changes during minimally invasive abdominal surgery and contribute to the development of strategies for optimizing renal protection and perioperative patient management

Inclusion Criteria:

• Patients aged 18 to 80 years
• Patients with ASA physical status I, II, or III
• Patients undergoing elective minimally invasive abdominal surgery for any reason
• Patients whose expected surgical duration is longer than 1 hour

Exclusion Criteria:

• Body mass index greater than 35 kg/m²
• Severe respiratory system disease
• Severe heart failure, NYHA class III-IV
• Presence of a cardiac pacemaker or cardiac defibrillator implant
• Progressive neuromuscular disease
• High intra-abdominal pressure
• Sudden deterioration of general condition
• Incomplete clinical or laboratory data
• Refusal to participate in the study
• Conversion to open surgery

Adult patients aged 18-80 years with ASA physical status I-III undergoing elective minimally invasive abdominal surgery at Istanbul University-Cerrahpaşa Faculty of Medicine. Patients will be prospectively evaluated for perioperative renal perfusion using Doppler ultrasonography and Near-Infrared Spectroscopy (NIRS).

Individual participant data (IPD) will not be shared because the study was not designed with a data-sharing plan and participant confidentiality will be protected in accordance with institutional and ethical requirements.