Indocyanine Green Fluorescence Angiography in Colorectal Cancer Surgery After a Decade of Randomized Trials: From Visual Assessment to Quantification and Beyond

Anastomotic leakage (AL) remains one of the most serious complications of colorectal cancer surgery, and inadequate perfusion is one of the few causes that surgeons can cor-rect intraoperatively. Indocyanine green fluorescence angiography (ICG-FA) shows intes-tinal perfusion in real time and is widely used. Meta-analyses of randomized trials show that ICG-FA reduces overall AL by about one-third, mainly after left-sided and rectal anastomoses, although most individual trials missed their primary endpoints, and effects after right-sided resection and on grade C AL remain unproven. We explore why the trials appeared to disagree and what this implies for perfusion assessment. We consider statis-tical precision, anatomical site, leak severity, endpoints, diversion and neoadjuvant treat-ment, imaging protocols, and interpretation, then review quantitative perfusion analysis, hyperspectral and laser speckle contrast imaging, near-infrared-II imaging, and artificial intelligence. The apparent disagreement is compatible with limited precision for a moder-ate common effect, as the trials were powered for reductions of about 40% or more; differ-ences in endpoints and technique mean that they answered somewhat different questions. Separately, imaging physics and observer variability suggest that the weak point of ICG-FA is how fluorescence is measured and read. Until objective methods are shown to improve clinical outcomes, ICG-FA should be performed with a standardized protocol.