This is a prospective, multicentre, non-randomized cohort study using real-time intraoperative visualization of bowel perfusion by indocyanine green (ICG) in all-cause bowel ischemia.

At intraoperative finding of bowel ischemia, the initial intraoperative plan is noted and resection margins marked with a steril pen. A fluorescence angiography will be performed and the surgeon will note whether the suspected ischemic bowel is perfused, whether there is a change in the resection margins in centimeters, and if the intraoperative plan has changed. If resection is indicated and the strategy of choice is an anastomosis, a renewed fluorescence angiography will be performed to assess anastomotic perfusion.

Fluorescence guided-surgery utilises the fluorescent property of a fluorophore, indocyanine green (ICG), injected intravenously to assess perfusion and viability of the bowel.

This study aims to evaluate the usability and feasibility of ICG to assess bowel viability in an emergency abdominal surgery setting where all-cause bowel ischemia is suspected and intraoperatively present. The investigators aim to evaluate whether ICG fluorescence angiography contributes as an intraoperative aid and changes the intraoperative strategy.

The investigators hypothesize that ICG is a safe and reliable aid in intraoperative decision-making regarding mesenteric ischemia. It may lead to an increasing number of one-step definitive procedures with vital resection margins, primary anastomosis and reducing stomas, and second-look procedures.

In this prospective, non-randomized cohort study bowel viability will be assessed using intraoperative real-time visualization by performing an ICG-fluorescence angiography when there is intraoperative finding of bowel ischemia.

Intraoperatively, ICG (Verdye, Diagnostic Green GmbH 25 mg vials) are dissolved with 5 ml sterile water obtaining a concentration of 5 mg/ml. 0,2mg/kg will be administered intravenously at one to two steps of perfusion assessment.

Initially, the surgeon notes the intended intraoperative plan before fluorescing and if resection is deemed necessary, the resection margins will be marked with a sterile pen.

The perfusion assessment with ICG is then performed and perfusion of the suspected ischemic bowel is noted, along with any change in intended resection margins and intraoperative plan. If an anastomosis is performed, a renewed perfusion assessment is performed. The perfusion assessment will be recorded.

Postoperatively, a subgroup of suitable perfusion assessment recordings will be subject to quantification software using software developed and validated by the investigators (q-ICG).

The trial follows regulations for research in emergency settings and a written and oral informed consent will be obtained from the participant or the participants next of kin and a trial guardian, postoperatively.

Intra- and postoperative clinical data will be collected, including choice of strategy, anastomotic leaks, 30- and 90- day complications, and mortality rates.

Inclusion Criteria:

• Adult patients >18 years of age
• Acute physiologic derangement and suspected of having bowel ischemia
• Intraoperative finding of all-cause bowel ischemia with subsequent acute physiologic derangement

Exclusion Criteria:

• Allergy toward; iodine, indocyanine green, or shellfish
• Liver insufficiency
• Thyrotoxicosis
• Pregnancy or lactation
• Permanently legally incompetent for any reason