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September 02, 2021, 01:55

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Indocyanine green (ICG) emits an infrared signal when excited by laser light in situ. This signal can be detected with a near-infrared fluorescence (NIF) camera. NIF imaging uses laser technology to activate an intravenously delivered agent, ICG, which rapidly binds to plasma proteins. This allows ICG to remain predominantly in the vasculature enabling visual assessment of blood flow and tissue perfusion, sentinel lymph node biopsy, and lymph node road mapping. In this issue of the World Journal of Gastroenterology, the review article by Zocola et al. highlights the role of NIF in colorectal surgery. They have reviewed the literature on the use of NIF for three main indications: estimation of intestinal vascularization to detect areas of poor perfusion to prevent anastomotic leakage; visualization of sentinal lymphatic drainage and peritoneal metastases; and examination of the ureter to reduce the risk of iatrogenic ureteral lesions in colorectal surgery. NIF in conjunction with ICG allows visualization of the microcirculation before development of the anastomosis, thereby allowing the surgeon to choose the point of transaction in an optimally perfused area. Zocola et al. have intensively reviewed the role of NIF in intraoperative assessment of bowel viability for prevention of anastomotic leaks. They assessed the findings of retrospective cohort and prospective randomized controlled studies and reviewed the effectiveness of NIF in reducing anastomotic leakage. Regarding the role of NIF with ICG in detecting metastatic lymph nodes, Zocola et al. reviewed studies on the identification of sentinel lymph nodes and mapping of additional lymph nodes outside the proposed resection margins to achieve curative radical lymphadenectomy. In addition to the studies described by Zocola et al., I would like to discuss some recent relevant literature. One of the issues related to radical lymphadenectomy in colorectal cancer is lateral pelvic node dissection (LPND), and the data on this procedure using NIF have been recently reported. Kim et al. [1] demonstrated a novel application of NIF using ICG during robotic total mesorectal excision (TME) with LPND to identify suspected lateral pelvic lymph nodes and prevent incomplete dissection. They injected ICG at a dose of 2.5 mg around the tumor transanally before surgery, and NIF imaging–guided robotic TME with lateral pelvic lymphadenectomy allowed the surgeon to identify lymph nodes and lymphatic flow of rectal cancer. Zhou et al. [2] compared patients who underwent TME and LPND with the NIF technique (n = 12) and those who received conventional TME and LPND without NIF-guided imaging (n = 30). They reported that the NIF group had significantly lower intraoperative blood loss (55.8 ± 37.5 mL vs 108.0 ± 52.7 mL, P = 0.003) and a significantly larger number of lateral pelvic nodes harvested (11.5 ± 5.9 vs 7.1 ± 4.8, P = 0.017), and lateral pelvic lymph nodes from two patients in the NIF group remained during LPND. Additionally, Park et al. [3] used the NIF technique for colorectal cancer surgery for D3 lymphadenectomy, especially for right-sided colon cancer. They injected ICG around the tumor for visualization of lymphatic flow and lymph nodes and demonstrated that the number of apical lymph nodes (14 vs. 7, p < 0.001) and total harvested lymph nodes (39 vs. 30, p = 0.003) were significantly higher in the NIF group than in the conventional group. When injected intravenously, ICG rapidly binds to plasma proteins and remains predominantly in the vasculature. Although this has not been mentioned in this review article, NIF angiography can be used to examine the vascular system. ICG can be easily injected into blood vessels during surgery allowing direct visual observation of vascular structure. Bae et al. [4] studied 11 patients who underwent robotic TME with preservation of the left colic artery for rectal cancer using the NIF technique. The optimal point of division was then chosen by the surgeon under NIF imaging, which facilitated identification of the left colic branch of the inferior mesenteric artery (IMA). NIF imaging was also used to identify the collateral vessels (arc of Riolan) around the inferior mesenteric vein in their study. The left colic artery branches mainly at the Griffith point (watershed), which is located in the splenic bend, where the left branch of the middle colic and the ascending branch of the left colic join. This area is vulnerable to intraoperative injury and ischemia due to poor blood supply. Therefore, great care must be taken to avoid injuring the bifurcation of the left colic artery. Real-time identification of collateral vessels using NIF technology can help perform safe low ligation of the IMA while preventing damage to these vessels. Currently, it remains a linear graded outcome that requires subjective interpretation of the demarcation point between sufficient and insufficient perfusion, and perfusion is assessed based on the subjective qualitative impression of the surgeon. Quantitative analysis of NIF images is desirable but is not currently available in robotic or laparoscopic systems. Son et al. [5] performed a quantitative evaluation of colon perfusion patterns using NIF angiography to identify the most reliable predictive factor of anastomotic complications after laparoscopic colorectal surgery. They found that the fluorescence slope, T1/2MAX, and time ratio were related to anastomotic complications, which were significantly correlated with the novel factor time ratio (> 0.6) as the most reliable predictor of perfusion and anastomotic complications. Recently, Han et al. [6] compared the changes in perfusion status between high tie and low tie through quantitative evaluation of ICG using NIF. They demonstrated that T_max increased and Slope_max decreased significantly in the high-tie group after IMA ligation, whereas the intensity of perfusion status (F_max), which indicates the intensity of perfusion, did not change according to the level of IMA ligation. They suggested that the speed of blood perfusion could be more delayed after high tie than after low tie, but the intensity of perfusion was similar between high and low ligation of the IMA. There are still many questions and debates requiring resolution, but we believe that the NIF technique will play an important role in improving the clinical and oncologic outcomes of colorectal surgery. References 1 Kim HJ, Park JS, Choi GS, Park SY, Lee HJ. Fluorescence-guided robotic total mesorectal excision with lateral pelvic lymph node dissection in locally advanced rectal cancer: A video presentation. Dis Colon Rectum 2017; 60(12): 1332-3. 2 Zhou SC, Tian YT, Wang XW et al. Application of indocyanine green-enhanced near-infrared fluorescence-guided imaging in laparoscopic lateral pelvic lymph node dissection for middle-low rectal cancer. World J Gastroenterol 2019; 25(31): 4502-11. 3 Park SY, Park JS, Kim HJ, Woo IT, Park IK, Choi GS. Indocyanine green fluorescence imaging-guided laparoscopic surgery could achieve radical D3 dissection in patients with advanced right-sided colon cancer. Dis Colon Rectum 2020; 63(4): 441-9. 4 Bae SU, Min BS, Kim NK. Robotic low ligation of the inferior mesenteric artery for rectal cancer using the firefly technique. Yonsei Med J 2015; 56(4): 1028-35. 5 Son GM, Kwon MS, Kim Y, Kim J, Kim SH, Lee JW. Quantitative analysis of colon perfusion pattern using indocyanine green (ICG) angiography in laparoscopic colorectal surgery. Surg Endosc 2019; 33(5): 1640-9. 6 Han SR, Lee CS, Bae JH et al. Quantitative evaluation of colon perfusion after high versus low ligation in rectal surgery by indocyanine green: A pilot study. Surg Endosc 2021. 1. Kim HJ, Park JS, Choi GS, Park SY, Lee HJ. Fluorescence-guided Robotic Total Mesorectal Excision with Lateral Pelvic Lymph Node Dissection in Locally Advanced Rectal Cancer: A Video Presentation. Dis Colon Rectum. 2017;60(12):1332-1333. 2. Zhou SC, Tian YT, Wang XW, Zhao CD, Ma S, Jiang J, et al. Application of indocyanine green-enhanced near-infrared fluorescence-guided imaging in laparoscopic lateral pelvic lymph node dissection for middle-low rectal cancer. World J Gastroenterol. 2019;25(31):4502-4511. 3. Park SY, Park JS, Kim HJ, Woo IT, Park IK, Choi GS. Indocyanine Green Fluorescence Imaging-Guided Laparoscopic Surgery Could Achieve Radical D3 Dissection in Patients With Advanced Right-Sided Colon Cancer. Dis Colon Rectum. 2020;63(4):441-449. 4. Bae SU, Min BS, Kim NK. Robotic Low Ligation of the Inferior Mesenteric Artery for Rectal Cancer Using the Firefly Technique. Yonsei Med J. 2015;56(4):1028-1035. 5. Son GM, Kwon MS, Kim Y, Kim J, Kim SH, Lee JW. Quantitative analysis of colon perfusion pattern using indocyanine green (ICG) angiography in laparoscopic colorectal surgery. Surg Endosc. 2019;33(5):1640-1649. 6. Han SR, Lee CS, Bae JH, Lee HJ, Yoon MR, Al-Sawat A, et al. Quantitative evaluation of colon perfusion after high versus low ligation in rectal surgery by indocyanine green: a pilot study. Surg Endosc. 2021. doi:10.1007/s00464-021-08673-x.

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