In this non-interventional, multicenter study in the Central Denmark Region, the potential of assessing blood supply during colorectal surgery will be explored using a recognized and reliable laser technique called Laser Speckle Contrast Imaging. The study aims to evaluate whether surgeons find this tool valuable in the decision-making process regarding where to perform the anastomosis during the operation.

Anastomotic leakage (AL) is among the most severe and feared postoperative complications of colorectal surgery as it is directly associated with an increase in mortality and morbidity. AL increases risk of local recurrence, decreases the 5-year survival rate, and impairs the patient's quality of life. Despite improvements in the surgical technique, AL continues to occur with high frequency. The cause of AL is considered multifactorial and several factors have shown association with increased risk of AL, although the complete pathogenesis is still unclear; It is recognized that one of the most important risk factors is inadequate blood supply to the anastomotic site, since optimal perfusion is essential for the healing of the anastomosis.

Currently, the assessment of the perfusion at the anastomotic site is based on a subjective clinical estimate by the surgeon (e.g., palpable pulsation of the arteries in the mesenterium, normal color of the intestine, bleeding from the surgical edges, and/or pulsatile bleeding from marginal arteries). However, these assessments are shown to lack objectivity, quantifiability, and predictive accuracy - even experienced surgeons underestimate the risk of AL.

Preventing AL is crucial for improving the outcomes of colorectal surgery. Studies have shown that understanding the state of microcirculation can help reduce the rate of AL. Therefore, having an accurate evaluation of local intestinal microcirculation is the first step in aiding surgeons to make informed decisions on the optimal anastomotic side.

Laser Speckle Contrast Imaging (LSCI) is a dye-free non-contact, non-invasive image-based method, capable of quantitative estimation of the local intestinal perfusion. Further, it allows for time-independent repeated measurements. LSCI uses laser light to generate a speckle pattern: When an object is in motion or contains moving particles such as blood cells, the interference between beams is affected, leading to variations in the phases and the creation of a dynamic speckle pattern. Based on the movements of the red blood cells, LSCI can be used to assess the blood flow within the tissue (microcirculation). Thus, LSCI cannot measure absolute flow but rather measures contrast changes and results are expressed as flux in arbitrary laser speckle perfusion units (LSPU), where higher LSPU values correspond to better tissue perfusion. LSCI is validated and used in small animal and human studies of the gastro-intestinal tract but has not yet been thoroughly tested in a true clinical setting.

LSCI has been utilized in various clinical contexts, including the gastrointestinal system, demonstrating ease and safety of use. However, there is only one similar study from 2019 in Japan where measurements were conducted on 8 patients undergoing colon surgery. The limitations of this study include its single-center nature, involvement of only one surgeon, and a lack of description regarding the surgeons' perspectives on LSCI measurements - whether they consider it a useful tool in their intraoperative procedures. Recently, another study has been published employing LSCI to measure the colon intraoperatively. Nevertheless, this study utilizes a newly developed laparoscopic-based LSCI technique, and it compares surgeons' subjective assessments of the technique. The findings indicate a high level of satisfaction, with 67% of surgeons expressing a willingness to make changes during surgery based on the images. Despite numerous clinical studies supporting the feasibility of LSCI, the literature on colon surgery lacks sufficient evidence to generalize the use of open LSCI equipment across all operating rooms as a tool for surgeons, despite its demonstrated potential.

It is hypothesized that LSCI is a method that could help surgeons evaluate and qualify the peri-operative intestinal microcirculation when anastomoses are formed.

The aim of this study is to investigate this hypothesis.

Study objectives:

1. To provide a descriptive analysis of using LSCI during colorectal surgery to assess microcirculation in the intestines before and after anastomosis formation and evaluate the feasibility of the method.
2. To assess the surgeon's subjective perception whether LSCI could be a useful tool to aid their decision-making during surgery.

Inclusion Criteria:

• All patients undergoing any elective colorectal surgery with the potential formation of an extracorporeal anastomosis as part of the surgical procedure are eligible for inclusion, irrespective of the indication for surgery. Patients will be consecutively included, after informed consent.

Exclusion Criteria:

• In this clinical feasibility trial, exclusion criteria apply only in cases where the inclusion criteria are not met or if performing an extracorporeal anastomosis is not feasible during surgery. Otherwise, patients meeting the inclusion criteria will be considered eligible for participation in the trial.

Patients will be identified and included from the Regional Hospital Gødstrup, Viborg, and Randers.

There are so few patients that Danish GDP data cannot be shared as it cannot be anonymized, which would be in violation of Danish data protection law.