Prospective Observational Evaluation of Renal Perfusion Using Doppler Ultrasonography and Near-Infrared Spectroscopy in Patients Undergoing Elective 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.