What is the role of Indocyanine Green (ICG) injection in assessing perfusion of the anastomotic site after resection anastomosis using the Olympus 3D system with ICG mode?

ICG Fluorescence Angiography for Anastomotic Perfusion Assessment

Indocyanine green (ICG) fluorescence angiography should be used intraoperatively when available to assess anastomotic perfusion after bowel resection and anastomosis, as it can identify inadequate perfusion that is not visible to the naked eye and may reduce anastomotic leak rates. 1

Guideline-Based Recommendation

The World Journal of Emergency Surgery guidelines explicitly state that ICG fluorescence angiography is a valid tool for evaluating the extent of bowel resection and anastomosis perfusion when available. 1 This recommendation applies specifically to:

• Assessment of intestinal viability after resection 1
• Evaluation of anastomosis perfusion to define resection margins more accurately 1
• Intraoperative decision-making regarding bowel viability 1

Technical Implementation with Olympus 3D ICG Mode

Timing of ICG Administration

• Inject ICG intravenously (typically 2.5-5 mg) after completing the anastomosis but before closing the abdomen 2, 3
• Average time to intestinal wall contrasting is approximately 42 seconds (range 22-65 seconds) 3
• The entire ICG assessment procedure adds only about 4 minutes to total operative time (approximately 3.2% of surgery duration) 3

Interpretation Parameters

The most critical parameter for predicting anastomotic leak is T0 (time from ICG injection to beginning of fluorescence): 2

• Normal perfusion: T0 < 25 seconds 2
• Poor perfusion/high leak risk: T0 > 60 seconds 2
• Patients with anastomotic leakage had significantly longer T0 times (64.3 ± 27.6 seconds) compared to those without leakage (18.2 ± 6.6 seconds, p = 0.002) 2

Clinical Decision-Making Based on ICG Findings

If ICG reveals inadequate perfusion at the planned anastomotic site: 4, 3, 5

• Extend the resection proximally to well-perfused tissue (the "optizone") 4
• In 22-26% of cases, ICG imaging will reveal inadequate perfusion not apparent on visual inspection alone 4, 5
• In approximately 4-5% of cases, ICG may require changing the transection line by more than 50 mm 5

Evidence for Clinical Benefit

Reduction in Anastomotic Leak Rates

The strongest evidence shows that performing anastomosis in the ICG-defined "optizone" reduces leak rates from 18% to 3% (p = 0.04). 4 Additional supporting data:

• Zero anastomotic leaks in 41 patients when ICG was used versus 8.6% leak rate without ICG 3
• When anastomosis was performed in areas of compromised ICG perfusion, 100% developed leaks (2/2 patients) 4

Discordance Between Visual Assessment and ICG

• In 22.8% of cases, ICG angiography findings deviated from visual assessment of conduit perfusion 4
• ICG identified intestinal ischemia requiring extended resection in 7.3% of patients that was not apparent visually 3

Risk Factors for Poor Perfusion Identified by ICG

Independent risk factors for inadequate intestinal perfusion on ICG imaging include: 5

• Anticoagulation therapy (p = 0.021) 5
• Preoperative chemotherapy (p = 0.019) 5
• Diabetes mellitus (univariate analysis) 5
• Prolonged operative time (univariate analysis) 5

These patients warrant particularly careful ICG assessment and lower threshold for extending resection margins. 5

Critical Pitfalls to Avoid

• Never proceed with anastomosis in an area showing delayed or absent ICG fluorescence - this has 100% leak rate in reported series 4
• Do not rely solely on visual inspection of bowel color and peristalsis - ICG reveals inadequate perfusion in approximately 1 in 4 cases that appear viable visually 4, 5
• Do not skip ICG assessment in high-risk patients (those on anticoagulation or who received preoperative chemotherapy) as they have significantly higher rates of poor perfusion 5
• Ensure adequate time (at least 60-90 seconds) for ICG circulation before concluding perfusion is adequate 2, 3

Technique for Vessel Clamp Method

For complex cases with prior surgeries (such as patients with ileal conduits), use the vessel clamp technique with both positive and negative staining: 6

• First, clamp the vessels supplying the area in question 6
• Inject ICG and observe for negative staining (absence of fluorescence) to confirm the clamped vessels are the primary blood supply 6
• After resection and anastomosis, inject ICG again to confirm positive staining (presence of fluorescence) in the remaining conduit or anastomosis 6
• This technique clearly visualizes the demarcation line between ischemic and non-ischemic intestinal tract 6

Quality of Evidence Considerations

While the guideline recommendation carries "very low" quality of evidence 1, the research evidence is compelling with consistent findings across multiple studies showing reduced leak rates and high sensitivity for detecting inadequate perfusion. The intervention is low-risk, adds minimal operative time, and has potential for significant reduction in a devastating complication. 3