The Role of Intraoperative Indocyanine Green Fluorescence Angiography in Reducing Anastomotic Leak After Colorectal Resection: A Systematic Review of Randomised Controlled Trials

Anastomotic leak (AL) has a reported incidence of 3%-19% after colorectal resection.The aim of this Preferred Reporting Items of Systematic Reviews and Meta-analyses (PRISMA) 2020 compliant systematic review is to determine whether intraoperative indocyanine green fluorescence angiography (ICG-FA) reduces clinically significant anastomotic leak and improves peri-operative outcomes compared with standard white-light assessment in adults undergoing colorectal resection with primary anastomosis.We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science from inception to March 2026.Eligible study designs included randomised controlled trials (RCTs) enrolling adults undergoing elective colorectal resection with primary anastomosis and comparing intraoperative ICG-FA with standard white-light assessment.The primary outcome was "clinically relevant anastomotic leak" as defined by the International Study Group of Rectal Cancer.Six RCTs enrolling 4,366 randomised patients, of whom 4,221 were evaluable: FLAG (n=377), De Nardi et al. (n=240), EssentiAL (n=839), AVOID (n=931), ICG-COLORAL (n=1,136), and IntAct (n=698).EssentiAL was the only trial to demonstrate a statistically significant reduction in all-grade AL (7.6% (32/422) vs 11.8% (49/417); relative risk (RR) 0.645; p=0.041) and grade B/C AL (4.7% (20/422) vs 8.2% (34/417); p=0.044).AVOID, ICG-COLORAL, and IntAct did not meet their primary endpoints but consistently favoured left-sided resections in subgroup analyses.IntAct showed an absolute five percentage-point reduction in grade B/C AL (10% (36/343) vs 15% (54/355); adjusted odds ratio (OR) 0.667; 95% confidence interval (CI) 0.419-1.060;p=0.087).No serious ICG-related adverse events were reported.Grading of Recommendations Assessment, Development, and Evaluation (GRADE) certainty of evidence for the primary outcome was moderate.Current RCT evidence does not support routine ICG-FA across all colorectal anastomoses.Leak rates are most consistently reduced for left-sided and low rectal resections where inferior mesenteric artery (IMA) ligation may compromise anastomotic perfusion.