**3. The use of ICG in surgery**

#### **3.1 General aspects**

Fluorescence imaging techniques have become increasingly common in recent years. ICG-based fluorescence, in particular, is now widely used in a variety of diagnostic and treatment procedures, according to the research made by Nowaka and co [2]. ICG is currently the most commonly used fluorescent agent due to its gradual degradation and the rarity of the severe adverse effects described. ICG is a watersoluble, amphiphilic tricarbocyanine probe with a molecular weight of 776 Da, relatively nontoxic, unstable compound, a dye in clinic use bound by albumin in the intravascular space until rapid clearance by the liver. Severe allergic reactions associated with the use of ICG are very rare (1:10,000) with an incidence of 0.05% and mostly occur in patients allergic to iodine. It has various applications in different

*The Use of Indocyanine Green in Colorectal Surgery DOI: http://dx.doi.org/10.5772/intechopen.100301*

fields, such as cardiology, ophthalmology, and neurosurgery, but its fluorescent properties have only recently been applied to the intraoperative estimation of tissue blood supply. Apart from ICG, other substances can act as fluorophores (fluorescent chemical compounds that are able to reemit light upon light excitation), such as methylene blue, five-aminolevulinic acid, fluorescein sodium.

What is fluorescence-guided surgery (FSG)? FSG is employed because white visible light makes various tissues appear either identical or highly similar, and proper tumor identification can be difficult, according to www.isfgs.org [3]. Moreover, the surgeon just sees the tissues from the superficial layers under natural light. Nonetheless, structures that were previously invisible can be seen now and recognized by using ICG in a different light length. By combining visual abilities with special dyes, it is now possible to avoid such organs or structures during the surgical process in order to avoid harming them. Other benefits of the FSG include the ability to minimize operative time and the need for second-look procedures by facilitating the rapid detection of structures and lesions while avoiding excessive harm.

#### **3.2 The use of ICG in general surgery interventions, outside the colorectal area**

ICG has found application in several fields of general surgery, especially colorectal surgery (seen in the next section of the present article), esophageal surgery, and emergency evaluation of intestinal perfusion in cases of mesenteric ischemia, kidney transplantation, hepatobiliary, and endocrine surgery.

#### *3.2.1 ICG in peritoneal carcinomatosis*

ICG can improve the harvesting of tumors during surgery and can properly adjust both the indications, as the extent of the intervention. In a systematic review performed in 2020 by Baiocchi [4], which took into account 192 screened papers with six series meeting the eligibility criteria, there were analyzed in total 353 peritoneal nodules, the neoplasms in question being—colorectal, hepatocellular, ovarian, endometrial. The above-mentioned study had as a purpose to look at the available clinical data regarding the value of ICG fluorescence imaging for intraoperative detection of peritoneal carcinomatosis during open surgery and the main aspects studied settled to the conclusion that sensitivity varied from 72.4 to 100%, while the specificity ranged from 54.2 to 100%.

#### *3.2.2 ICG in liver surgery*

The ICG fluorescence method is being used more and more in liver surgery due to the fact that it permits the real-time display of the segmental anatomy of the organ, depending on the tumor's characteristics, and, more so, it is possible to perform direct or indirect identification of hepatic lesions and metastases. Additionally, ICG imaging allows more sensitive detection of tumor foci and, therefore, also a higher R0 resection rate. However, in a systematic review of the literature on the application of ICG imaging in open and laparoscopic liver surgery performed by Sucher et al. [5], the conclusion was drawn toward the aspect that the application resulted mainly useful for superficial lesions, as the depth of penetration of NIR is only 8–10 mm. In liver resections, post-hepatectomy liver failure (PHLF) can occur although an adequate liver volume is kept in place. Diverse dynamic functional tests, such as the indocyanine green test (ICG), could only appreciate globally the liver function, with no definition toward the functional ability of the hepatic remnant. Magnetic resonance imaging (MRI) with liver-specific

contrast agents makes the evaluation of both liver function and volume possible. A preoperative combination between dynamic quantitative tests, such as ICG, with MRI or HBS (hepato-bilio-scintigraphy), should provide a more complete functional evaluation. One should opt for various functional tests to predict PHLF that should be selected according to patient's characteristics, disease, and center experience, as shown by Tomassini and the team [6].

#### *3.2.3 ICG-NIR to assess skin flap perfusion*

The incidence of skin flap necrosis after mastectomies can reach 11–24%. Laser-assisted ICG angiography appears as a promising technique to assess skin flap perfusion. In a systematic review performed by Driessen et al. [7], it was found that all studies looking at the current ICG methodology and ability to predict outcome showed a substantial decrease in skin necrosis when the ICG was used.

#### *3.2.4 ICG-NIR to assess peritoneal endometriosis*

Endometriosis is a very commonly encountered disease that is found in up to 10% of the female population. The use of (ICG) has been advocated for the proper location of endometriotic lesions intraoperatively. NIR-ICG is useful in appreciating the blood supply of bowel anastomoses after segmental resection, according to a systematic review done by Ianieri et al. [8] that looked at 53 studies.

#### *3.2.5 ICG to identify the ureter*

Iatrogenic ureteral injury in abdominal surgery is rare at the moment, although it can still result in significant morbidity and mortality. Inspection and palpation are two traditional methods of measuring iatrogenic ureteral damage, which can be difficult during laparoscopic procedures. The use of NIRF imaging to aid in better visualization of the ureters is currently being investigated. The report's goal performed by Slooter et al. [9] was to picture the currently available and experimental dyes in ureter visualization and to further evaluate their feasibility of using them and, more so, to look at their effectiveness.

### *3.2.6 ICG to identify a bleeding site in the GI area*

Several studies, among which the one performed by Copaescu [10], aimed to look at the reliability of a novel fluorescence-guided laparoscopic technique to correctly find the site of unknown gastrointestinal bleeding, with the help of the vascular washout properties of indocyanine green (ICG). The bleeding site was correctly identified and the patient benefited from a minimally invasive technique, and it was, therefore, possible to avoid an open surgical exploration.

#### *3.2.7 ICG in sentinel lymph node in different neoplasms*

This represents another important topic in different surgical fields, for instance, urology, gynecology, and general surgery.

#### *3.2.7.1 Breast cancer*

In the early stage of breast cancer, ICG-fluorescence-based sentinel lymph node (SLN) detection is being considered. A systematic review looking at 2301 patients from 19 studies found that ICG-fluorescence could complement the radioisotope

method or provide an alternative. Another study regarding the ICG lymph node technique in breast cancer was a literature review presented by Benson [11] in which a significantly better sentinel node detection rate was found with ICG than with the standard radioisotope method (**Figure 5**).
