Preoperative Injection of Indocyanine Green Fluorescence at the Anorectal Junction Safely Identifies the Inferior Mesenteric Artery in a Prospective Case-Series Analysis of Colorectal Cancer Patients

Background: Indocyanine green (ICG)-guided surgery is an emerging technique to enhance intraoperative visualization of nodes and tumor location. However, there is no uniform protocol regarding the optimal timing, dosage, or injection site for ICG in colorectal cancer surgery. We assess the feasibility of ICG injection at the anorectal junction immediately before surgery to safely identify the inferior mesenteric artery (IMA). Methods: This was a prospective study involving robotic left hemicolectomy or anterior resection of the rectum for primary colorectal cancer in 2024 in a single center. A total of 10–20 mg was injected into the anorectal submucosa at four quadrants circumferentially using an anoscope immediately before robot docking. Results: In this first study, ICG allowed us to identify the IMA in 84.6% of 26 patients (mean age 66.5 years; BMI 26.7 kg/m2), without intraoperative medical and surgical complications. Elevated BMI correlated with failure of IMA detection (r = −0.77, p < 0.001), despite high ICG doses trending toward improved vascular visualization (p = 0.097). A mean of 22 lymph nodes was harvested after ICG injection, with yields unaffected by the quality of IMA visualization. Conclusions: Submucosal injection of ICG is a feasible and easily adoptable option for early identification of the IMA, thereby preventing major vascular injuries, particularly in patients with challenging anatomy. A standardized protocol was implemented to improve reliability.