**Abstract**

This chapter looks at the use of indocyanine green (ICG) in colorectal surgery, by exploring at first the definition of vital dyes generally used in the surgical field, afterward the benefits of fluorescence-guided surgery, and furthermore, it enumerates several uses of ICG in the broad surgical field. The identification of tumor nodules in the peritoneum can help with proper cancer staging, and the same advantage is brought by the accurate detection of the sentinel lymph node, which concerns the use of ICG specifically in colorectal surgery, and this can be summed up through the following assets brought by the technique: (a) intraoperative fluorescence angiography as an adjuvant in the process of anastomosis, (b) fluorescence-guided detection of lymph node metastases in colorectal cancer and the sentinel lymph node technique, which was proved better than formal methods in some studies, (c) the positive fluorescence of a liver nodule as small as "only" 200 tumor cells, (d) the help in diagnosing a fistula, (e) the possibility to be used for tumor tattooing also, and (f) the help in maintaining a clean surgical field and preventing wound infection in abdominoperineal resection.

**Keywords:** colorectal, fluorescence, ICG, ICG-NIR, colorectal surgery, intraoperative staining

## **1. Introduction**

As the general surgical techniques have polished with more and more precise gestures, which in time lead to the appearance and development of even robotic surgery, the same phenomenon happened when it comes to adjuvant methods to better identify, visualize, and resect a specific structure/tissue during the intervention. Fluorescence can bring important assets when it comes to seeing better—the vessels, the lymph nodes, and the tumor itself. Some organs, such as the case of the ureter, are also much better underlined with the technique of NIR-ICG (nearinfrared light and indocyanine green [ICG]), and therefore, the risk of producing a lesion secondary to incomplete visualization is smaller. This chapter closely looks at the literature on the theme of ICG in colorectal surgery, offering also a general frame made out of significant research, mainly systematic reviews and randomized controlled trials about the use of ICG in visceral surgery.
