EP2004 - Discordant Perfusion of the Descending Colon in Indocyanine Green-Fluorescence Angiography and Laser Speckle Contrast Imaging Leading to Completion Colectomy

Purpose/Background: Anastomotic leak (AL) is a serious complication of colorectal surgery with a reported incidence of 3% to 19%. Multi-modal imaging in minimally invasive surgery aims to improve the assessment of local bowel perfusion, a critical determinant of anastomotic healing. Indocyanine Green-Fluorescence Angiography (ICG-FA) and Laser Speckle Contrast Imaging (LSCI) have each been shown to alter intra-operative decisions, though their effect on AL is inconclusive. Currently, there is limited data to understand the concordance and variable benefits of ICG-FA versus LSCI in clinical practice. We present a case of discordant perfusion assessment of the descending colon in ICG-FA and LSCI impacting surgical decision-making.

Methods/Interventions: A 62-year-old female presenting with a 3-month history of abdominal pain, oral intolerance, and weight loss was diagnosed with smoldering diverticulitis. Initial CT imaging revealed concern for cecal mass with no evidence of metastatic disease (Figure 1). When deemed appropriate, she underwent attempted colonoscopy, which was incomplete due to fixation of the sigmoid colon with diverticulosis. Superficial biopsy of the cecal mass was performed, revealing villous adenoma. She was evaluated by colorectal surgery and underwent laparoscopic, right hemicolectomy with sigmoid colectomy. In the operating room, the intervening transverse and descending colon conduit appeared healthy under white light. Under ICG-FA, the conduit revealed adequate perfusion. Subsequent assessment with LSCI revealed notable perfusion attenuation to the colon conduit (Figure 2). Discordance between perfusion assessment tools was re-demonstrated on repeated evaluation, and colo-rectal anastomosis was therefore deferred. Ultimately, a completion colectomy with ileo-rectal anastomosis and diverting loop ileostomy were performed.

Results/Outcomes: The patient progressed appropriately and was discharged home on post-operative day 5. Final pathology revealed T3N0 invasive adenocarcinoma of the ileocecal valve and diverticulosis of the sigmoid colon. She underwent uncomplicated reversal of her diverting loop ileostomy 3-months later. She continues to be monitored for routine colon cancer surveillance.

Conclusion/Discussion: To our knowledge, this is the first report demonstrating significant perfusion discordance between ICG-FA and LSCI. When compared previously in two clinical studies, ICG-FA and LSCI were concordant in 95% and 83% of cases, without a statistically significant difference. The difference observed in our case is therefore a unique clinical scenario and may be related to the mechanisms by which the two modalities assess perfusion. ICG is a plasma bound fluorophore which represents blood volume within a tissue of interest. As an injectable fluorophore, ICG is limited by subjective green signal interpretation and false positives over time related to capillary leakage and stagnant blood flow. These limitations provide insight into the heterogenous effect of ICG-FA on reducing AL across randomized trials. In contrast, LSCI utilizes laser refraction of moving red blood cells to assess tissue perfusion. As LSCI does not rely on an injectable dye, its deployment is real-time, allowing for repeated assessments throughout a prolonged procedure, as in the case presented above. Overall, this case highlights the integration of multi-modal imaging in the operating room as well as the ongoing challenges and advancements in bowel perfusion assessment.

Figure 1. CT of the Abdomen and Pelvis Demonstrating Cecal Thickening and Diverticula of the Sigmoid Colon
Panel A shows a coronal view CT A/P demonstrating cecal thickening (red arrow) and diverticula of the sigmoid colon (yellow arrow). Panels B and C are axial CT views demonstrating sigmoid diverticula (yellow arrow) and cecal thickening (red arrow) respectively.
Figure 2. Colonic Perfusion Assessment in Indocyanine Green-Fluorescence Angiography (ICG-FA) and Laser Speckle Contrast Imaging (LSCI)
Panel A demonstrates the local tissue perfusion assessment of the distal descending colon (circle) and rectum (diamond) in ICG-FA while Panel B demonstrates the perfusion assessment in LSCI. ICG-FA and LSCI display concordant perfusion of the rectal stump (diamond), however there is discordance in perfusion of the distal descending colon (circle).