Endoscopic COlorectal Mucosal Evaluation of Oxygen Tension

Virtually all patients undergoing elective colon and rectal resections undergo bowel anastomosis. These surgeries are often technically challenging, with significant morbidity and mortality in the case of an anastomotic leak, which can affect up to 21% of patients. In addition to increased morbidity and mortality, anastomotic leaks are associated with increased hospital length of stay and cost. Anastomotic leak following colon and rectal surgery is multifactorial, involving an intimate interplay of patient-related, tumor, and surgical risk factors. While decreased perfusion to anastomosis plays a central role in its pathophysiology. Poor perfusion at the anastomotic site can also lead to anastomotic strictures - requiring further reoperations , and in some cases, be equally catastrophic as anastomotic leaks.

As such, multiple attempts have been made to reduce the incidence of leaks. It is believed that the ability to accurately determine intraoperative tissue perfusion and oxygenation can help reduce the incidence of anastomotic leaks. Investigators have explored multiple modalities and benchmarks in human and animal models over the past three decades; these include colonic coloration, mesenteric pulsations, tissue perfusion using Doppler ultrasound quantitative visual analysis of tissue oxygenation using either indocyanine green or non-contrast tissue oxygenation imaging tools to detect predictors of anastomotic leak and hyperbaric oxygenation in mice models to improve anastomotic healing. While a few studies have found an association between low tissue oxygen tension and anastomotic leak development, there have only been a handful of large-scale human studies.

Currently, indocyanine green fluorescence angiography (ICG-FA) is the most widely accepted in this regard. It has shown a significant reduction in anastomotic leaks owing to a change in the resection margin. However, ICG-FA is contraindicated in patients with a history of contrast allergy. It also has a higher plasma disappearance, leading to an unstable fluorescence signal for the estimation of tissue congestion, causing reduced precision in estimates and an introduction of subjectivity and reduced standardization; furthermore, it cannot be repeated intraoperatively because of the increased risk of false positives. The newer imaging modalities focus on tissue oxygen tension (StO2) by mapping oxygen saturation indices. They utilize multispectral illumination to accurately quantify StO2 levels by distinguishing between oxyhemoglobin and deoxyhemoglobin without the need for fluorescent dyes or repeat intraoperative evaluations, thereby improving efficiency and accuracy.

Studies that have used StO2 to predict anastomotic leak after colo-rectal surgery in humans have utilized serosal oxygen tension, and these have established safety, usability, and reliability, along with exploration of the link with anastomotic leak. However, since the mucosa exhibits the first signs of hypoxia, it might be a better target for predicting postoperative anastomotic complications. Such a theory has been explored using the Food and Drug Administration (FDA) 510k approved device (FUJIFILM Eluxeo Vision system; K203717) among patients undergoing thoracic esophagectomy, in which the results followed the aforementioned hypothesis. However, there is no literature on such an imaging modality used for colon and/or rectal resections and anastomosis.

In this prospective observational study we aim to investigate the association between mucosal StO2 levels and the incidence of anastomotic complications, including stricture and leak in colo-rectal surgery. We hypothesize that lower StO2 will be associated with higher anastomotic complications (stricture and leak [grades A, B, or C], as determined by the surgeon).

Inclusion criteria

• Adult patients (≥18 years).
• Undergoing a colo-rectal anastomosis.
• Patients who consent to study participation

Exclusion criteria

• Patients undergoing a revision surgery.
• Participants with missing data.
• Patients who do not undergo intraoperative ICG-FA and StO2 endoscopic imaging promptly after the formation of a viable anastomosis.