Importance: Performing a bowel anastomosis is a critical step in colorectal resection. Assessing the risk of anastomotic leakage remains challenging, even for experienced surgeons.

Objective: To evaluate the use of indocyanine green (ICG) fluorescence imaging in assessing perfusion at the anastomotic site before and after anastomosis and determine whether it helps reduce anastomotic leakages.

Design, setting, and participants: ICG-COLORAL is a prospective, randomized, multicenter study conducted from September 1, 2018, to December 31, 2023. Participants were recruited during preoperative outpatient clinic visits by clinicians not involved in the study, as well as by researchers. Participants were elective patients scheduled for laparoscopic resections, excluding low anterior resections, with planned primary anastomosis in 5 Finnish public hospitals experienced in laparoscopic colorectal surgery.

Intervention: The intervention group received 5 mg of ICG intravenously before and after anastomosis formation. The fluorescence signal was assessed with a near-infrared-capable camera. The control group did not receive ICG fluorescence imaging.

Main outcome and measure: The primary outcome measure was the anastomotic leak rate as detected by computed tomography.

Results: Among 1136 patients in the intention-to-treat population, 526 (46.3%) were female and 610 (53.7%) male; they had a mean (SD) age of 70 (11) years, body mass index of 28 (5), and age-adjusted Charlson Comorbidity Index of 5 (3). Overall, the anastomotic leak rate was 5.8% (33/567) in the ICG fluorescence imaging group vs 7.9% (45/569) in the control group (odds ratio [OR], 0.73; 95% CI, 0.48-1.13; P = .16). For right-sided operations, the anastomotic leak rate with ICG fluorescence imaging was 5.9% (16/273) vs 6.7% (20/298) in the control group (OR, 0.87; 95% CI, 0.46-1.65). For left-sided operations, the anastomotic leak rate was 5.2% (14/267) with ICG fluorescence imaging vs 9.5% (23/243) without (OR, 0.55; 95% CI, 0.29-1.05). No patients reported adverse events related to ICG.

Conclusions and relevance: This study found that routine use of ICG fluorescence imaging does not significantly reduce the overall anastomotic leak rate in laparoscopic colorectal surgery if low anterior resections are excluded but may be beneficial in left-sided operations.

Trial registration: ClinicalTrials.gov Identifier: NCT03602677.