Background : Disappearing colorectal liver metastasis has become increasingly common with improved response to systemic therapy. Not only does it pose a therapeutic dilemma, it is also a challenge for surgeons to accurately identify the lesion for excision intraoperatively. Firefly ICG assistance has been shown to be a useful adjunct for identifying subcapsular liver tumours intraoperatively, even in situations when the lesion is too small to be seen on intraoperative ultrasound.

Methods : We present the case of a 61-year-old gentleman with rectal adenocarcinoma and an isolated synchronous liver metastasis in subcapsular segment 7. The liver lesion responded well to neoadjuvant chemotherapy and decreased in size from 0.6cm to 0.3cm on pre-operative imaging. The patient underwent combined robotic assisted ultralow anterior resection and wedge resection of the segment 7 liver metastasis. 0.25mg/kg of ICG was given intravenously 3 days prior to surgery.

Results : Intraoperatively, a small focus of positive ICG staining was seen in subcapsular liver segment 7, although the lesion was too small to be seen on intraoperative ultrasound. There were scattered positive staining foci in the rest of the liver. Imaging correlation for expected anatomical location correlating to potential site of positive staining was done. A wedge resection of the segment 7 lesion was performed. No pringles was applied and blood loss was 50mls. Histology returned as a 0.2cm metastatic adenocarcinoma which was completely excised.

Conclusions : Intraoperative Firefly ICG assistance in addition to preoperative imaging correlation is a useful adjunct for intra-operative localisation of subcapsular disappearing colorectal liver metastasis.