Background:Fluorescence guided imaging with indocyanine green (ICG) has been shown to aid resection of colorectal liver metastases. We describe our technique of Fluorescence guided imaging for resection and margin determination of metachronous colorectal liver metastases in a patient with unilobar tumor burden. Methods:A 78-year-old-man with a history of right hemicolectomy and adjuvant chemotherapy for stage III right colon cancer presented 2 years later with increasing CEA and a new suspicious liver lesion on PET. MRI showed two adjacent hypoenhancing lesions in segment VIII spanning 4.5cm concerning for metastases. Due to a history of multiple prior abdominal operations and lesions present near the posterior dome, the patient was scheduled for open right metastatectomy. Results: A total of 5cc of ICG was administered intravenously twenty-four hours prior to surgery. Intraoperative visualization of tumor measured 3.5cm with the naked eye, 4.5cm with the ultrasound, and extended to 5.5cm with ICG fluorescence. ICG perfused area extended farther and deeper than what would be margin traditionally resected using the ultrasound. The tumor was resected completely. The operative time was. 420 minutes. The total blood loss was 1500cc. Final pathology showed a total of 4cm of tumor involvement with a 1.5cm circumferential margin. The patient was discharged on postoperative day seven. He remains disease free at 12 months follow up. Conclusions:Fluorescence guided imaging with ICG is a useful tool in oncologic resection of colorectal liver metastases. ICG dispersion may overestimate the margin of liver resection