Impact of Riolan arch and mesenteric vascular anatomy on tissue oxygenation in rectal cancer surgery: A prospective study on inferior mesenteric artery ligation strategies.

Abstract

The optimal management of the inferior mesenteric artery during rectal cancer surgery, specifically whether to preserve the left colic artery using low-tie ligation or perform high-tie ligation, remains a subject of debate. This study aims to propose a preoperative strategy for left colic artery preservation by evaluating the role of Riolan arch and mesenteric vascular anatomy in modulating tissue oxygen partial pressure during inferior mesenteric artery ligation. In a cohort of 109 rectal cancer patients, preoperative computed tomography angiography was used to evaluate vascular anatomy, including the diameters of the inferior mesenteric artery and superior mesenteric artery, as well as the presence of Riolan arch. Intraoperative oxygen partial pressure was measured in 44 patients using Clark electrodes during sequential clamping of the inferior mesenteric artery. Patients were subsequently stratified based on the status of Riolan arch, the type of inferior mesenteric artery, and the diameter of superior mesenteric artery. Postoperative diameters of the inferior mesenteric artery significantly decreased, whereas the superior mesenteric artery diameters remained stable. Patients with Riolan arch (25.00%) demonstrated shorter distances between the inferior mesenteric artery and the superior mesenteric artery. Clamping of the inferior mesenteric artery resulted in a significant reduction in oxygen partial pressure levels, whereas clamping of the superior rectal artery had minimal effects. The presence of Riolan arch was associated with a rebound in oxygen partial pressure levels at 2.5 minutes post-clamping, which was not observed in patients without the Riolan arch. Larger superior mesenteric artery diameters (≥9.2 mm) mitigated the decline in oxygen partial pressure. Patients with type I inferior mesenteric artery exhibited lower baseline oxygen partial pressure levels, and body mass index was found to influence the rate of oxygen partial pressure decline. Riolan arch and superior mesenteric artery diameter are critical factors influencing colonic oxygenation during inferior mesenteric artery ligation. Continuous monitoring of oxygen partial pressure indicates that patients lacking Riolan arch and with superior mesenteric artery diameters smaller than 9.2 mm might benefit from left colic artery preservation. These results underscore the importance of implementing personalized surgical approaches guided by preoperative vascular mapping.