Indocyanine green fluorescence angiography during laparoscopic rectal surgery

Advances in medical equipment and surgical techniques have enabled surgeons to offer patients better oncological and clinical outcomes after colorectal resections. However, anastomotic leakage remains one of the most serious postoperative complications in rectal surgery. The rate of anastomotic leakage after rectal surgery has been reported at 6% to 14% (1-4). In particular, low anastomoses have a considerably higher risk of leakage compared to intraperitoneal ones (1,2). Anastomotic leakage results in increased length of hospital stay, health care cost, morbidity, and mortality rates (3,4). In addition, anastomotic leakage has been found to negatively impact prognosis on local recurrence and cancer specific survival (5).

There are many risk factors related to anastomotic leakage. Risk factors can be categorized as patient-related, disease-related, and intraoperative-related. Patient-related risk factors include gender, body mass index (BMI), nutrition, and American Society of Anesthesiologists (ASA) score (1-3,6). Disease-related factors include level of anastomosis, neoadjuvant therapy, and tumor size (1,2,6). These risk factors may be beyond the influence of the surgeons. Conversely, intraoperative-related factors including blood perfusion to the anastomotic tissue, tension on the anastomosis, operative time, blood loss, and number of stapler firings (2,6-8), can be controlled by the surgeons. Among these factors, blood perfusion is thought to be an important factor for avoiding anastomotic leakage. Adequate blood supply is crucial for successful healing, and avoidance of intestinal ischemia and necrosis (6-8). Anastomotic leakage and stricture may be attributed to inadequate perfusion of anastomotic tissue.

Accurate determination of the resection margin of the viable bowel may help to reduce anastomotic leakage. The selection of an optimal site for anastomosis has been dependent on the surgeons’ gross inspection. Intestinal microperfusion and viability is usually estimated intraoperatively from clinical parameters, such as color of the bowel wall, presence of bowel peristalsis, bleeding from the edges of the bowel, and palpable pulsations of mesenteric arteries. However, this assessment is subjective and based on the surgeons’ experience. Karliczek et al. (9) evaluated the accuracy of the surgeons’ gross inspection for anastomotic leakage occurrence in a prospective clinical study. The surgeons’ ability to predict anastomotic leakage appeared to be low in gastrointestinal surgery, with a sensitivity of 61.3% and a specificity of 88.5%. Thus, objective and reliable intraoperative methods to assess bowel viability are required.

There are several different intraoperative assessment of anastomotic microperfusion, such as Doppler technology, tissue oxygen tension, and oxygen spectroscopy (10,11). However, due to equipment cost, complex maneuvers, lack of reproducibility, and the need for a specialist, these techniques have thus far been experimental and have not achieved widespread clinical acceptance. In recent years, indocyanine green fluorescence angiography (ICG-FA) has proved useful in assessing real-time microperfusion intraoperatively and can apply to open, laparoscopic, and robotic surgery.

ICG is a sterile, anionic, water-soluble, tricarbocyanine compound dye that serves as an optical contrast agent. It absorbs near-infrared (NIR) light at 800–810 nm and emits it at a slightly longer wavelength of 830 nm. Following intravenous injection, ICG rapidly and extensively binds to plasma proteins, and is confined to the intravascular compartment. It is cleared by the liver in 3 to 5 minutes and excreted via the bile within 10–15 minutes. ICG has been safely used clinically in many countries for over 30 years. ICG exhibits a low toxicity with few adverse events (12,13). However, ICG contains sodium iodide and therefore should be used with care in patients with an iodine allergy. Special camera filters are necessary to visualize the ICG fluorescence. The light needed for the excitation of the fluorescence is generated by a near infrared light source which is attached directly to a camera. This camera allows the absorption of the ICG fluorescence to be recorded in real time. ICG-FA is suitable for use as an intraoperative imaging tool, and has been associated with improved outcomes in coronary, transplant, plastic surgery, and a number of other surgical procedures (14). ICG-FA was validated for assessing bowel microperfusion in a pig ischemia model (15). The fluorescence intensity was directly correlated with tissue perfusion, and ICG-FA could effectively detect the demarcation between ischemic and vascular areas.

There are several recent articles which describe the usefulness of ICG-FA for colorectal surgery with first report published by Kudszus et al. (16). They reported that ICG-FA led to a change of the initially planned proximal transection line in 13.9% (28/201) of cases. ICG-FA significantly reduced anastomotic leakage rate in colorectal surgery by 4% compared to a historical control group (3.5% vs. 7.5%). ICG-FA during colorectal surgery has also been described in other non-randomized studies (17-22). Jafari et al. (17) reported the results of a multi-institutional prospective single armed study, PILLAR-II that assessed the feasibility and utility of ICG-FA in left-sided colorectal resections. In this study, ICG-FA obtained successful imaging in 98.6% (137/139) of cases. The overall anastomotic leakage rate was 1.4% (2/139). ICG-FA led to change in the surgical plan in 8% (11/139) of cases, with most changes occurring at the time of transection of the proximal margin due to hypoperfusion, and no anastomotic leakage occurred in these patients. However, the height of anastomosis from the anal verge was higher than or equal to 8 cm in 74.1% (103/139) of cases and this study did not focus on total mesorectal excision (TME).

There are very few articles focused on the use of ICG-FA during rectal surgery with TME, which has a higher risk of leakage compared to colon surgery, and the rate of diverting stoma is higher (18,19). Boni et al. focused on rectal surgery with TME and reported that ICG-FA was safe and effective. ICG-FA influenced the surgical strategy in 4.7% (2/42) of cases and there was no anastomotic leakage (0/42) in low rectal cancer resection. Gröne et al. (18) also reported that the overall anastomotic leakage rate was 5.6% (1/18) in low rectal and anorectal anastomoses.

Most of the studies were focused on the change in surgical decision making, however there are a few studies that have reported on the reduction in anastomotic leakage rate (16,20,21). Boni et al. reported that the anastomotic leakage rate was 0% and 5.2% in the ICG-FA group and historical control group, respectively. A recent systematic review showed that ICG-FA of colorectal anastomosis was associated with a significantly lower risk of anastomotic leakage compared with a control group without ICG-FA (3.8% vs. 7.6%; P=0.0055) (20). Only one retrospective case-matched study by Kin et al. (21) revealed that there was no difference in anastomotic leakage rate in colorectal resection between the ICG-FA group and control group. The authors acknowledged several limitations of their study such as the retrospective nature of the study, selection bias and the small sample size.

There are several limitations of ICG-FA. First, the surgeons’ assessment of the intensity of perfusion is subjective. One study attempted to evaluate the fluorescence intensity by a five step score (“1” indicating no uptake and “5” indicating maximal uptake) but this assessment did not clearly show any conclusion regarding the predictive value of an abnormal ICG-FA (19). Another study aimed to quantify the fluorescence intensity level by using specially designed software that calculated the steepness of the light emission curve (pixel intensity per second) in order to achieve a more objective perfusion assessment (16). Unfortunately, this study did not lead to a cut-off value to quantify the fluorescence intensity, which is needed to minimize observational variability between surgeons. The ideal time to perfusion after injection of ICG is unknown. Kawada et al. (22) reported that the median time to perfusion was 35 seconds. However, the association between the time and poor perfusion is unclear. Therefore, ICG-FA remains subjective until more objective cut-off levels for sufficient perfusion are established.

Secondly, ICG-FA can be influenced by various conditions, such as distance, surrounding lighting, the dose of ICG injection and the effect of repeated ICG injections. The distance between the tip of the camera and subject, and the operating room lighting may affect the fluorescence intensity (23). The optimal dose of ICG injection prior to assessment is unknown. The fluorescence intensity of ICG is almost linearly increased with concentration within a low concentration range, while the fluorescence intensity peaks and subsequently decreases at a higher concentration, a phenomenon known as the ‘quenching effect’, and is an important consideration (23). This effect cannot be controlled by the surgeon and lower concentrations are recommended to avoid this problem. However, the dose of ICG varies according to the studies. The effect of repeated injections of ICG is unknown and has not been investigated (24).

In conclusion, ICG-FA enables the surgeon to ensure sufficient blood supply to the anastomosis. ICG-FA is easily reproducible, cost effective, incurs little additional time, and has limited adverse effects. ICG-FA may prevent anastomotic leakage in patients undergoing colorectal surgery. However, no randomized controlled trials have been published and the present studies lack a high level of evidence therefore the clinical benefit of ICG-FA is inconclusive. A large, randomized, controlled trial, PILLAR-III, could determine if ICG-FA would have a positive impact on anastomotic leakage rate in rectal surgery.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Laparoscopic and Endoscopic Surgery. The article did not undergo external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/ales.2016.12.09). MI serves as an unpaid editorial board member of Annals of Laparoscopic and Endoscopic Surgery from Oct 2016 to Sep 2018. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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