ICG fluorescence imaging for quantitative evaluation of colonic perfusion in laparoscopic colorectal surgery

Real time organ hypoperfusion detection using Indocyanine Green in a piglet model

BACKGROUND

Preserving sufficient oxygen supply to the tissue is fundamental for maintaining organ function. However, our ability to identify those at risk and promptly recognize tissue hypoperfusion during abdominal surgery is limited. To address this problem, we aimed to develop a new method of perfusion monitoring that can be used during surgical procedures and aid surgeons' decision-making.

METHODS

In this experimental porcine study, thirteen subjects were randomly assigned one organ of interest [stomach (n = 3), ascending colon (n = 3), rectum (n = 3), and spleen (n = 3)]. After baseline perfusion recordings, using high-frequency, low-dose bolus injections with weight-adjusted (0.008 mg/kg) ICG, organ-supplying arteries were manually and completely occluded leading to hypoperfusion of the target organ. Continuous organ perfusion monitoring was performed throughout the experimental conditions.

RESULTS

After manual occlusion of pre-selected organ-supplying arteries, occlusion of the peripheral arterial supply translated in an immediate decrease in oscillation signal in most organs (3/3 ventricle, 3/3 ascending colon, 3/3 rectum, 2/3 spleen). Occlusion of the central arterial supply resulted in a further decrease or complete disappearance of the oscillation curves in the ventricle (3/3), ascending colon (3/3), rectum (3/3), and spleen (1/3).

CONCLUSION

Continuous organ-perfusion monitoring using a high-frequency, low-dose ICG bolus regimen can detect organ hypoperfusion in real-time.

Quantitative analysis of intestinal perfusion with indocyanine green (ICG) and methylene blue (MB) using a single clinically approved fluorescence imaging system: a demonstration in a porcine model

BACKGROUND

Near-infrared fluorescence (NIRF) angiography with intraoperative administration of indocyanine green (ICG) has rapidly disseminated in clinical practice. Another clinically approved, and widely available dye, methylene blue (MB), has up to now not been used for this purpose. Recently, we demonstrated promising results for the real-time evaluation of intestinal perfusion using this dye. The primary aim of this study was to perform a quantitative analysis of bowel perfusion assessment for both ICG and MB.

METHODS

Four mature female Landrace pigs underwent laparotomy under general anesthesia. An ischemic bowel loop with five regions of interest (ROIs) with varying levels of perfusion was created in each animal. An intravenous (IV) injection of 0.25 mg/kg-0.50 mg/kg MB was administered after 10 min, followed by NIRF imaging in MB mode and measurement of local lactate levels in all corresponding ROIs. This procedure was repeated in ICG mode (IV dose of 0.2 mg/kg) after 60 min. The quest spectrum fluorescence camera (Quest Medical Imaging, Middenmeer, The Netherlands) was used for NIRF imaging of both MB and ICG.

RESULTS

Intraoperative NIRF imaging of bowel perfusion assessment with MB and ICG was successful in all studied animals. Ingress (i/s) levels were calculated and correlated with local lactate levels. Both MB and ICG ingress values showed a significant negative correlation (r = - 0.7709; p =  < 0.001; r = - 0.5367, p = 0.015, respectively) with local lactate levels. This correlation was stronger for MB compared to ICG, although ICG analysis showed higher absolute ingress values.

CONCLUSION

Our fluorescence quantification analysis validates the potential to use MB for bowel perfusion assessment besides the well-known and widely used ICG. Further human studies are necessary to translate our findings to clinical applications.

Perfusion Mapping of Flaps Using Indocyanine Green Fluorescence Angiography and Laser Speckle Contrast Imaging

Background

Indocyanine green fluorescence angiography (ICG-FA) is often used for assessing tissue circulation in reconstructive surgery. Indocyanine green (ICG) is injected intravenously and visualized in the tissue with an infrared camera. The information is used to plan the surgery, for example, in free flap breast reconstructions. Laser speckle contrast imaging (LSCI) is another method that uses laser to assess tissue perfusion in the skin. Unlike ICG-FA, LSCI is noninvasive and may therefore have an advantaged compared with ICG-FA. The aim of this study was to evaluate the correlation between information obtained from these two techniques.

Methods

Five deep inferior epigastric perforator patients were included. The flaps were assessed with LSCI and ICG-FA. For LSCI, the perfusion was calculated in 32 regions of interest. For ICG-FA, the maximum slope and area under curve (AUC) were calculated based on average pixel intensity data.

Results

Large variations in maximum slope values could be seen between flaps, whereas AUC had lower variability within the same flap and between flaps. Pearson rank correlation comparing average perfusion (LSCI) and AUC (ICG-FA) showed a correlation between the values (r = 0.55, P < 0.0001). No significant correlation was observed between perfusion and maximum slope (r = 0.11, P = 0.18).

Conclusions

There is a significant correlation between data obtained using LSCI and ICG-FA, when ICG-FA data are presented as AUC of the ICG-FA intensity curve. Maximum slope lacks significant correlation with flap data obtained with LSCI. The study indicates that LSCI may be used in reconstructive surgery to assess tissue circulation in a way similar to ICG-FA.

Clinical and computational development of a patient-calibrated ICGFA bowel transection recommender

INTRODUCTION

Intraoperative indocyanine green fluorescence angiography (ICGFA) aims to reduce colorectal anastomotic complications. However, signal interpretation is inconsistent and confounded by patient physiology and system behaviours. Here, we demonstrate a proof of concept of a novel clinical and computational method for patient calibrated quantitative ICGFA (QICGFA) bowel transection recommendation.

METHODS

Patients undergoing elective colorectal resection had colonic ICGFA both immediately after operative commencement prior to any dissection and again, as usual, just before anastomotic construction. Video recordings of both ICGFA acquisitions were blindly quantified post hoc across selected colonic regions of interest (ROIs) using tracking-quantification software and computationally compared with satisfactory perfusion assumed in second time-point ROIs, demonstrating 85% agreement with baseline ICGFA. ROI quantification outputs detailing projected perfusion sufficiency-insufficiency zones were compared to the actual surgeon-selected transection/anastomotic construction site for left/right-sided resections, respectively. Anastomotic outcomes were recorded, and tissue lactate was also measured in the devascularised colonic segment in a subgroup of patients. The novel perfusion zone projections were developed as full-screen recommendations via overlay heatmaps.

RESULTS

No patient suffered intra- or early postoperative anastomotic complications. Following computational development (n = 14) the software recommended zone (ROI) contained the expert surgical site of transection in almost all cases (Jaccard similarity index 0.91) of the nine patient validation series. Previously published ICGFA time-series milestone descriptors correlated moderately well, but lactate measurements did not. High resolution augmented reality heatmaps presenting recommendations from all pixels of the bowel ICGFA were generated for all cases.

CONCLUSIONS

By benchmarking to the patient's own baseline perfusion, this novel QICGFA method could allow the deployment of algorithmic personalised NIR bowel transection point recommendation in a way fitting existing clinical workflow.

Comparison of the perioperative outcomes of using the Firefly system with indocyanine green during robotic-assisted cystectomy with urinary diversion

INTRODUCTION

Use of indocyanine green (ICG) with near-infrared fluorescence (NIRF) has been demonstrated to be an effective tool for intraoperative assessment of bowel and ureteric vascularity. This study aimed to evaluate the impact of ICG on postsurgical outcomes such as anastomotic bowel leak and uretero-enteric stricture formation during robot-assisted cystectomy (RAC) and intracorporeal urinary diversion (ICUD).

METHODS

We identified 238 patients who underwent RAC at the University of Louisville between September 2012 and August 2021. Patients were divided into two groups based on the utilization of ICG. Demographic, perioperative outcomes, and rate of anastomotic bowel leak were compared.

RESULTS

In total, 138 patients were in the ICG group and 100 patients were in the non-ICG group. More intracorporeal urinary diversions and more simple cystectomies were observed in the ICG group (p < 0.001 and p = 0.015, respectively). The ICG group patients initiated an oral diet sooner than the control group (4.9 vs. 7.1 days, p < 0.001). The mean length of stay of the ICG group was shorter than the non-ICG group (8.3 vs. 12.8 days, p < 0.001). The rate of postoperative ileus was not significantly different between cohorts. No patients in the ICG group experienced a bowel leak compared with five patients in the non-ICG group (p = 0.008).

CONCLUSIONS

In our study, the use of ICG for intraoperative assessment of bowel and ureteric vascularity was associated with earlier bowel recovery and a shorter length of stay. It was also significantly correlated with a lower rate of anastomotic bowel leak.

Evaluation of gastric tube blood flow by multispectral camera and fluorescence angiography

Background

Evidence regarding the application of the multispectral camera for blood flow measurement is insufficient, and its performance has not been compared with the conventional indocyanine green (ICG) method. Therefore, we retrospectively compared the effectiveness of a new multispectral camera for non-invasive, real-time, quantitative imaging of tissue oxygen (O2) saturation and hemoglobin (Hb) levels and commercially available ICG fluorescence imaging in hemodynamic assessment of gastric tubes in esophagectomy.

Methods

Thirty patients who underwent thoracoscopic esophagectomy and gastric tube reconstruction for esophageal cancer were included in this study. The multispectral camera was used to measure tissue O2 saturation and Hb levels. The ICG fluorescence imaging, with the analysis software tool Lumi view, was employed to record ICG luminance changes, with values measured at the anastomotic site. Furthermore, the usefulness of each assessment device was examined using the arterial and venous blood flow indices as cutoff lines for cases with anastomotic failure.

Results

In the evaluation of arterial perfusion, anastomotic leak occurred in three of the five (60 %) patients with arterial insufficiency as assessed by the ICG imaging, while anastomotic leakage occurred in all three patients (100 %) who were assessed as having arterial insufficiency by the multispectral camera. In the evaluation of venous perfusion, anastomotic leakage occurred in three of the nine (33.3 %) patients diagnosed with venous stasis by the IC imaging and in three of the five (60 %) patients assessed by the multispectral camera.

Conclusion

The multispectral camera assessed gastric tube blood flow more accurately than the ICG fluorescence method.

Impact of standardising indocyanine green fluorescence angiography technique for visual and quantitative interpretation on interuser variability in colorectal surgery

AIM/BACKGROUND

Intra-operative colonic perfusion assessment via indocyanine green fluorescence angiography (ICGFA) aims to address malperfusion-related anastomotic complications; however, its interpretation suffers interuser variability (IUV), especially early in ICGFA experience. This work assesses the impact of a protocol developed for both operator-based judgement and computational development on interpretation consistency, focusing on senior surgeons yet to start using ICGFA.

METHODS

Experienced and junior gastrointestinal surgeons were invited to complete an ICGFA-experience questionnaire. They subsequently interpreted nine operative ICGFA videos regarding perfusion sufficiency of a surgically prepared distal colon during laparoscopic anterior resection by indicating their preferred site of proximal transection using an online annotation platform (mindstamp.com). Six ICGFA videos had been prepared with a clinical standardisation protocol controlling camera and patient positioning of which three each had monochrome near infrared (NIR) and overlay display. Three others were non-standardised controls with synchronous NIR and overlay picture-in-picture display. Differences in transection level between different cohorts were assessed for intraclass correlation coefficient (ICC) via ImageJ and IBM SPSS.

RESULTS

58 clinicians (12 ICGFA experts, 46 ICGFA inexperienced of whom 23 were either finished or within one year of finishing training and 23 were junior trainees) participated as per power calculations. 63% felt that ICGFA should be routinely deployed with 57% believing interpretative competence requires 11-50 cases. Transection level concordance was generally good (ICC = 0.869) across all videos and levels of expertise (0.833-0.915). However, poor agreement was evident with the standardised protocol videos for overlay presentation (0.208-0.345). Similarly, poor agreement was seen for the monochrome display (0.392-0.517), except for those who were trained but ICG inexperienced (0.877) although even here agreement was less than with unstandardised videos (0.943).

CONCLUSION

Colorectal ICGFA acquisition and display standardisation impacts IUV with this specific protocol tending to diminish surgeon interpretation consistency. ICGFA video recording for computational development may require dedicated protocols.

Indocyanine green (ICG) fluorescence-enhanced applications in pediatric surgery

The breadth of pediatric surgical practice and variety of anatomic anomalies that characterize surgical disease in children and neonates require a unique level of operative mastery and versatility. Intraoperative navigation of small, complex, and often abnormal anatomy presents a particular challenge for pediatric surgeons. Clinical experience with fluorescent tissue dye, specifically indocyanine green (ICG), is quickly gaining widespread incorporation into adult surgical practice as a safe, non-toxic means of accurately visualizing tissue perfusion, lymphatic flow, and biliary anatomy to enhance operative speed, safety, and patient outcomes. Experience in pediatric surgery, however, remains limited. ICG-fluorescence guided surgery is poised to address the challenges of pediatric and neonatal operations for a growing breadth of surgical pathology. Fluorescent angiography has permitted intraoperative visualization of colorectal flap perfusion for complex pelvic reconstruction and anastomotic perfusion after esophageal atresia repair, while its hepatic absorption and biliary excretion has made it an excellent agent for delineating the dissection plane in the Kasai portoenterostomy and identifying both primary and metastatic hepatoblastoma lesions. Subcutaneous and intra-lymphatic ICG injection can identify iatrogenic chylous leaks and improved yields in sentinel lymph node biopsies. ICG-guided surgery holds promise for more widespread use in pediatric surgical conditions, and continued evaluation of efficacy will be necessary to better inform clinical practice and identify where to focus and develop this technical resource.

[Prospects of qualitative and quantitative assessment of bowel perfusion by fluorescent angiography with indocyanine green in colorectal surgery. First experience]

OBJECTIVE

To assess the possibilities of fluorescent detection system in qualitative and quantitative assessment of bowel perfusion in colorectal resections.

MATERIAL AND METHODS

From May to August 2023, a single-center pilot cross-sectional unblinded study with inclusion of 18 patients with colon cancer (of left-sided - 12, of right-sided - 6, mean age - 72.9 years, m/w - 61/39%) was conducted. All patients underwent laparoscopic colorectal resections with extracorporeal stage of bowel transection. The evaluation of the bowel's ICG perfusion was conducted to assist in decision making about the level of its resection. Qualitative (visual) assessment was carried out in all 18 patients, in one patient twice, quantitative assessment of perfusion was conducted in 8 patients (left-sided resections - 6, right-sided hemicolectomy - 2). The qualitative evaluation was performed in real time on the analysis of the color gradient. The time parameters and fluorescence intensity at different level proximally and distally from the resection line were quantitatively estimated: Tstart - time of occurrence of minimal fluorescence in the areas of interest after the ICG injection (sec); Tmax - time to achieve maximum fluorescence intensity after the ICG injection (sec); Tmax-start - time interval between Tstart and Tmax, Imax - level of maximum fluorescence intensity (I).

RESULTS

Visual qualitative analysis of fluorescence revealed unsatisfactory perfusion characteristics (black, dark-gray color) in the area planned by the surgeon to anastomose the bowel in 3 of 18 patients (16.6%). When analyzing the quantitative data of this group of patients, there was a 2-6-fold decrease in Imax level, and one patient had an increase in Tmax-start at the level of intended resection compared to the bowel's sections in the favorable zone. In all cases, the final bowel transection was conducted in the area of good perfusion. There was no clinical evidence of anastomotic dehiscence in the study group.

CONCLUSION

Intraoperative evaluation of bowel perfusion is an important component of safe anastomosis formation in colorectal surgery. The use of ICG-FA allows to conduct qualitative and quantitative assessment of tissue perfusion of the bowel in order to assist in making intraoperative decisions. Quantitative evaluation of fluorescence provides more objective information about perfusion parameters. Imax and Tmax-start are the most promising quantitative indicators of local bowel's perfusion. Nevertheless, the precise interpretation of the quantitative indicators of ICG perfusion needs to be clarified.

Indocyanine green fluorescence in gastrointestinal surgery: Appraisal of current evidence

Applying indocyanine green (ICG) fluorescence in surgery has created a new dimension of navigation surgery to advance in various disciplines. The research in this field is nascent and fragmented, necessitating academic efforts to gain a comprehensive understanding. The present review aims to integrate diverse perspectives and recent advances in its application in gastrointestinal surgery. The relevant articles were selected by using the appropriate keyword search in PubMed. The angiography and cholangiography property of ICG fluorescence is helpful in various hepatobiliary disorders. In gastroesophageal and colorectal surgery, the lymphangiography and angiography property of ICG is applied to evaluate bowel vascularity and guide lymphadenectomy. The lack of objective parameters to assess ICG fluorescence has been the primary limitation when ICG is used to evaluate bowel perfusion. The optimum dose and timing of ICG administration need to be standardized in some new application areas in gastrointestinal surgery. Binding tumor-specific ligands with fluorophores can potentially widen the fluorescence application to detect primary and metastatic gastrointestinal tumors. The narrative review outlines prior contributions, limitations, and research opportunities for future studies across gastrointestinal sub-specialty. The findings of the present review would be helpful for scholars and practitioners to explore and progress in this exciting domain of gastrointestinal surgery.

Inferior Mesenteric Artery Ligation Level in Rectal Cancer Surgery beyond Conventions: A Review

Within the intricate field of rectal cancer surgery, the contentious debate over the optimal level of ligation of the inferior mesenteric artery (IMA) persists as an ongoing discussion, influencing surgical approaches and patient outcomes. This narrative review incorporates historical perspectives, technical considerations, and functional as well as oncological outcomes, addressing key questions related to anastomotic leakage risks, genitourinary function, and oncological concerns, providing a more critical understanding of the well-known inconclusive evidence. Beyond the dichotomy of high versus low tie, it navigates the complexities of colorectal cancer surgery with a fresh perspective, posing a transformative question: "Is low tie ligation truly reproducible?" Considering a multidimensional approach that enhances patient outcomes by integrating the surgeon, patient, technique, and technology, instead of a rigid and categorical statement, we argued that a balanced response to this challenging question may require compromise.

Usefulness of blood flow evaluation by indocyanine green fluorescence in laparoscopic or robot-assisted surgery for colorectal cancer with persistent descending mesocolon

A persistent descending mesocolon is defined as a congenital fixation anomaly caused by the defective membrane fusion of the descending colon and the lateral abdominal wall. Anatomically, in persistent descending mesocolon, the left colonic artery is often shortened, and joins the marginal artery soon after its bifurcation from the inferior mesenteric artery, while the colonic mesentery often adheres firmly to the mesentery of the small intestine. As a result of these characteristics, anatomical knowledge of the persistent descending mesocolon and preservation of bowel blood flow are important during surgery for left-sided colorectal cancer to avoid adverse events. Moreover, indocyanine green based blood flow assessment is useful for the detailed evaluation of bowel ischemia at the anastomotic site. Here we report the usefulness of blood flow evaluation using indocyanine green fluorescence in laparoscopic or robot-assisted surgery for three patients with colorectal cancer and persistent descending mesocolons.

Time required for indocyanine green fluorescence emission for evaluating bowel perfusion in left-sided colon and rectal cancer surgery

BACKGROUND

Indocyanine green fluorescence imaging (ICG-FI) has been reported to be useful in reducing the incidence of anastomotic leakage (AL) in colectomy. This study aimed to investigate the correlation between the required time for ICG fluorescence emission and AL in left-sided colon and rectal cancer surgery using the double-stapling technique (DST) anastomosis.

METHODS

This retrospective study included 217 patients with colorectal cancer who underwent left-sided colon and rectal surgery using ICG-FI-based perfusion assessment at our department between November 2018 and July 2022. We recorded the time required to achieve maximum fluorescence emission after ICG systemic injection and assessed its correlation with the occurrence of AL.

RESULTS

Among 217 patients, AL occurred in 21 patients (9.7%). The median time from ICG administration to maximum fluorescence emission was 32 s (range 25-58 s) in the AL group and 28 s (range 10-45 s) in the non-AL group (p < 0.001). The cut-off value for the presence of AL obtained from the ROC curve was 31 s. In 58 patients with a required time for ICG fluorescence of 31 s or longer, the following risk factors for AL were identified: low preoperative albumin [3.4 mg/dl (range 2.6-4.4) vs. 3.9 mg/dl (range 2.6-4.9), p = 0.016], absence of preoperative mechanical bowel preparation (53.8% vs. 91.1%, p = 0.005), obstructive tumor (61.5% vs. 17.8%, p = 0.004), and larger tumor diameter [65 mm (range 40-90) vs. 35 mm (range 4.0-100), p < 0.001].

CONCLUSION

The time required for ICG fluorescence emission was associated with AL.

Lymphatic flow mapping during colon cancer surgery using indocyanine green fluorescence imaging

With the development of surgical technology, indocyanine green (ICG) fluorescence navigation systems may be useful in various areas of colorectal surgery, including tumor location confirmation, bowel perfusion, ureter identification, and lymph node mapping. This review provides an overview of the current status of ICG-based navigation surgery in colorectal surgery, emphasizing its role in lymphatic flow mapping. This state-of-the-art approach will allow for appropriate oncological surgeries in the field of colorectal cancer and improve the patient's prognosis.

Application of fluorescence-guided surgery in the acute care setting: a systematic literature review

PURPOSE

Fluorescence-based imaging has found application in several fields of elective surgery, but there is still a lack of evidence in the literature about its use in emergency setting. The present review critically summarizes currently available applications and limitations of indocyanine green (ICG) fluorescence in abdominal emergencies including acute cholecystitis, mesenteric ischemia, and trauma surgery.

METHODS

A systematic review was performed according to the PRISMA statement identifying articles about the use of ICG fluorescence in the management of the most common general surgery emergency. Only studies focusing on the use of ICG fluorescence for the management of acute surgical conditions in adults were included.

RESULTS

Thirty-six articles were considered for qualitative analysis. The most frequent disease was occlusive or non-occlusive mesenteric ischemia followed by acute cholecystitis. Benefits from using ICG for acute cholecystitis were reported in 48% of cases (clear identification of biliary structures and a safer surgical procedure). In one hundred and twenty cases that concerned the use of ICG for occlusive or non-occlusive mesenteric ischemia, ICG injection led to a modification of the surgical decision in 44 patients (36.6%). Three studies evaluated the use of ICG in trauma patients to assess the viability of bowel or parenchymatous organs in abdominal trauma, to evaluate the perfusion-related tissue impairment in extremity or craniofacial trauma, and to reassess the efficacy of surgical procedures performed in terms of vascularization. ICG injection led to a modification of the surgical decision in 50 patients (23.9%).

CONCLUSION

ICG fluorescence is a safe and feasible tool also in an emergency setting. There is increasing evidence that the use of ICG fluorescence during abdominal surgery could facilitate intra-operative decision-making and improve patient outcomes, even in the field of emergency surgery.

Quantification of indocyanine green near-infrared fluorescence bowel perfusion assessment in colorectal surgery

BACKGROUND

Indocyanine green near-infrared fluorescence bowel perfusion assessment has shown its potential benefit in preventing anastomotic leakage. However, the surgeon's subjective visual interpretation of the fluorescence signal limits the validity and reproducibility of the technique. Therefore, this study aimed to identify objective quantified bowel perfusion patterns in patients undergoing colorectal surgery using a standardized imaging protocol.

METHOD

A standardized fluorescence video was recorded. Postoperatively, the fluorescence videos were quantified by drawing contiguous region of interests (ROIs) on the bowel. For each ROI, a time-intensity curve was plotted from which perfusion parameters (n = 10) were derived and analyzed. Furthermore, the inter-observer agreement of the surgeon's subjective interpretation of the fluorescence signal was assessed.

RESULTS

Twenty patients who underwent colorectal surgery were included in the study. Based on the quantified time-intensity curves, three different perfusion patterns were identified. Similar for both the ileum and colon, perfusion pattern 1 had a steep inflow that reached its peak fluorescence intensity rapidly, followed by a steep outflow. Perfusion pattern 2 had a relatively flat outflow slope immediately followed by its plateau phase. Perfusion pattern 3 only reached its peak fluorescence intensity after 3 min with a slow inflow gradient preceding it. The inter-observer agreement was poor-moderate (Intraclass Correlation Coefficient (ICC): 0.378, 95% CI 0.210-0.579).

CONCLUSION

This study showed that quantification of bowel perfusion is a feasible method to differentiate between different perfusion patterns. In addition, the poor-moderate inter-observer agreement of the subjective interpretation of the fluorescence signal between surgeons emphasizes the need for objective quantification.

Real-time quantification of bowel perfusion using Laparoscopic Laser Speckle Contrast Imaging (LSCI) in a porcine model

BACKGROUND/PURPOSE

Real-time quantification of tissue perfusion can improve intraoperative surgical decision making. Here we demonstrate the utility of Laser Speckle Contrast Imaging as an intra-operative tool that quantifies real-time regional differences in intestinal perfusion and distinguishes ischemic changes resulting from arterial/venous obstruction.

METHODS

Porcine models (n = 3) consisted of selectively devascularized small bowel loops that were used to measure the perfusion responses under conditions of control/no vascular occlusion, arterial inflow occlusion, and venous outflow occlusion using laser speckle imaging and indocyanine green fluoroscopy. Laser Speckle was also used to assess perfusion differences between small bowel antimesenteric-antimesenteric and mesenteric-mesenteric anastomoses. Perfusion quantification was measured in relative perfusion units calculated from the laser speckle perfusion heatmap.

RESULTS

Laser Speckle distinguished between visually identified perfused, watershed, and ischemic intestinal segments with both color heatmap and quantification (p < .00001). It detected a continuous gradient of relative intestinal perfusion as a function of distance from the stapled ischemic bowel edge. Strong positive linear correlation between relative perfusion units and changes in mean arterial pressure resulting from both arterial (R2 = .96/.79) and venous pressure changes (R2 = .86/.96) was observed. Furthermore, Laser Speckle showed that the antimesenteric anastomosis had a higher perfusion than mesenteric anastomosis (p < 0.01).

CONCLUSIONS

Laser Speckle Contrast Imaging provides objective, quantifiable tissue perfusion information in both color heatmap and relative numerical units. Laser Speckle can detect spatial/temporal differences in perfusion between antimesenteric and mesenteric borders of a bowel segment and precisely detect perfusion changes induced by progressive arterial/venous occlusions in real-time.

Intraoperative bowel perfusion assessment methods and their effects on anastomotic leak rates: meta-analysis

BACKGROUND

Anastomotic leak is one of the most feared complications of colorectal surgery, and probably linked to poor blood supply to the anastomotic site. Several technologies have been described for intraoperative assessment of bowel perfusion. This systematic review and meta-analysis aimed to evaluate the most frequently used bowel perfusion assessment modalities in elective colorectal procedures, and to assess their associated risk of anastomotic leak. Technologies included indocyanine green fluorescence angiography, diffuse reflectance spectroscopy, laser speckle contrast imaging, and hyperspectral imaging.

METHODS

The review was preregistered with PROSPERO (CRD42021297299). A comprehensive literature search was performed using Embase, MEDLINE, Cochrane Library, Scopus, and Web of Science. The final search was undertaken on 29 July 2022. Data were extracted by two reviewers and the MINORS criteria were applied to assess the risk of bias.

RESULTS

Some 66 eligible studies involving 11 560 participants were included. Indocyanine green fluorescence angiography was most used with 10 789 participants, followed by diffuse reflectance spectroscopy with 321, hyperspectral imaging with 265, and laser speckle contrast imaging with 185. In the meta-analysis, the total pooled effect of an intervention on anastomotic leak was 0.05 (95 per cent c.i. 0.04 to 0.07) in comparison with 0.10 (0.08 to 0.12) without. Use of indocyanine green fluorescence angiography, hyperspectral imaging, or laser speckle contrast imaging was associated with a significant reduction in anastomotic leak.

CONCLUSION

Bowel perfusion assessment reduced the incidence of anastomotic leak, with intraoperative indocyanine green fluorescence angiography, hyperspectral imaging, and laser speckle contrast imaging all demonstrating comparable results.

The Safe Values of Quantitative Perfusion Parameters of ICG Angiography Based on Tissue Oxygenation of Hyperspectral Imaging for Laparoscopic Colorectal Surgery: A Prospective Observational Study

BACKGROUND

Safe values for quantitative perfusion parameters of indocyanine green (ICG) angiography have not been fully defined, and interpretation remains at the surgeon's discretion. This prospective observational study aimed to establish the safe values for the quantitative perfusion parameters by comparing tissue oxygenation levels from HSI images in laparoscopic colorectal surgery.

METHODS

ICG angiography was performed using a laparoscopic near-infrared (NIR) camera system with ICG diluted in 10 mL of distilled water. For quantitative perfusion parameters, the changes in fluorescence intensity with perfusion times were analyzed to plot a time-fluorescence intensity graph. To assess real-time tissue oxygen saturation (StO2) in the colon, the TIVITA® Tissue System was utilized for hyperspectral imaging (HSI) acquisition. The StO2 levels were compared with the quantitative perfusion parameters derived from ICG angiography at corresponding points to define the safe range of ICG parameters reflecting good tissue oxygenation.

RESULTS

In the regression analysis, T1/2MAX, TMAX, slope, and NIR perfusion index were correlated with tissue oxygen saturation. Using this regression model, the cutoff values of quantitative perfusion parameters were calculated as T1/2MAX ≤ 10 s, TMAX ≤ 30 s, slope ≥ 5, and NIR perfusion index ≥50, which best reflected colon StO2 higher than 60%. Diagnostic values were analyzed to predict colon StO2 of 60% or more, and the ICG perfusion parameters T1/2MAX, TMAX, and perfusion TR showed high sensitivity values of 97% or more, indicating their ability to correctly identify cases with acceptable StO2.

CONCLUSION

The safe values for quantitative perfusion parameters derived from ICG angiography were T1/2MAX ≤ 10 s and TMAX ≤ 30 s, which were associated with colon tissue oxygenation levels higher than 60% in the laparoscopic colorectal surgery.

Quantification of Indocyanine Green Fluorescence Imaging in General, Visceral and Transplant Surgery

Near-infrared (NIR) imaging with indocyanine green (ICG) has proven to be useful in general, visceral, and transplant surgery. However, most studies have performed only qualitative assessments. Therefore, a systematic overview of all studies performing quantitative indocyanine green evaluation in general, visceral, and transplant surgeries should be conducted. Free term and medical subject heading (MeSH) term searches were performed in the Medline and Cochrane databases until October 2022. The main categories of ICG quantification were esophageal surgery (24.6%), reconstructive surgery (24.6%), and colorectal surgery (21.3%). Concordantly, anastomotic leak (41%) was the main endpoint, followed by the assessment of flap perfusion (23%) and the identification of structures and organs (14.8%). Most studies examined open surgery (67.6%) or laparoscopic surgery (23.1%). The analysis was mainly carried out using manufacturer software (44.3%) and open-source software (15.6%). The most frequently analyzed parameter was intensity over time for blood flow assessment, followed by intensity alone or intensity-to-background ratios for structure and organ identification. Intraoperative ICG quantification could become more important with the increasing impact of robotic surgery and machine learning algorithms for image and video analysis.

Fluorescence perfusion assessment of vascular ligation during ileal pouch-anal anastomosis

BACKGROUND

Intraoperative fluorescence angiography (FA) is of potential added value during ileal pouch-anal anastomosis (IPAA), especially after vascular ligation as part of lengthening measures. In this study, time to fluorescent enhancement during FA was evaluated in patients with or without vascular ligation during IPAA.

METHODS

This is a retrospective cohort study of all consecutive patients that underwent FA-guided IPAA between August 2018 and December 2019 in our tertiary referral centre. Vascular ligation was defined as disruption of the ileocolic arcade or ligation of interconnecting terminal ileal branches. FA was performed before and after ileoanal anastomotic reconstruction. During FA, time to fluorescent enhancement was recorded at different sites of the pouch.

RESULTS

Thirty-eight patients [55.3% male, median age 45 years (IQR 24-51 years)] were included, of whom the majority (89.5%) underwent a modified-2-stage restorative proctocolectomy. Vascular ligation was performed in 15 patients (39.5%), and concerned central ligation of the ileocolic arcade in 3 cases, interconnecting branches in 10, and a combination in 2. For the entire cohort, time between indocyanine green (ICG) injection and first fluorescent signal in the pouch was 20 s (IQR 15-31 s) before and 25 s (IQR 20-36 s) after anal anastomotic reconstruction. Time from ICG injection to the first fluorescent signal at the inlet, anvil and blind loop of the pouch were non-significantly prolonged in patients that received vascular ligation.

CONCLUSIONS

Results from this study indicate that time to fluorescence enhancement during FA might be prolonged due to arterial rerouting through the arcade or venous outflow obstruction in case of vascular ligation.

Real-time quantification of intestinal perfusion and arterial versus venous occlusion using laser speckle contrast imaging in porcine model

PURPOSE

Real-time intraoperative perfusion assessment may reduce anastomotic leaks. Laser speckle contrast imaging (LSCI) provides dye-free visualization of perfusion by capturing coherent laser light scatter from red blood cells and displays perfusion as a colormap. Herein, we report a novel method to precisely quantify intestinal perfusion using LSCI.

METHODS

ActivSight™ is an FDA-cleared multi-modal visualization system that can detect and display perfusion via both indocyanine green imaging (ICG) and LSCI in minimally invasive surgery. An experimental prototype LSCI perfusion quantification algorithm was evaluated in porcine models. Porcine small bowel was selectively devascularized to create regions of perfused/watershed/ischemic bowel, and progressive aortic inflow/portal vein outflow clamping was performed to study arterial vs. venous ischemia. Continuous arterial pressure was monitored via femoral line.

RESULTS

LSCI perfusion colormaps and quantification distinguished between perfused, watershed, and ischemic bowel in all vascular control settings: no vascular occlusion (p < 0.001), aortic occlusion (p < 0.001), and portal venous occlusion (p < 0.001). LSCI quantification demonstrated similar levels of ischemia induced both by states of arterial inflow and venous outflow occlusion. LSCI-quantified perfusion values correlated positively with higher mean arterial pressure and with increasing distance from ischemic bowel.

CONCLUSION

LSCI relative perfusion quantification may provide more objective real-time assessment of intestinal perfusion compared to conventional naked eye assessment by quantifying currently subjective gradients of bowel ischemia and identifying both arterial/venous etiologies of ischemia.

Continuous organ perfusion monitoring using indocyanine green in a piglet model

BACKGROUND

Unrecognized organ hypoperfusion may cause major postoperative complications with detrimental effects for the patient. The use of Indocyanine Green (ICG) to detect organ hypoperfusion is emerging but the optimal methodology is still uncertain. The purpose of this study was to determine the feasibility of real-time continuous quantitative perfusion assessment with Indocyanine Green (ICG) to monitor organ perfusion during minimally invasive surgery using a novel ICG dosing regimen and quantification software.

METHOD

In this experimental porcine study, twelve subjects were administered a priming dose of ICG, followed by a regimen of high-frequency (1 dose per minute), low-dose bolus injections with weight-adjusted (0.008 mg/kg) ICG allowing for continuous perfusion monitoring. In each pig, one randomly assigned organ of interest [stomach (n = 3), ascending colon (n = 3), rectum (n = 3) and spleen (n = 3)] was investigated with varying camera conditions. Video recording was performed with the 1588 AIM Stryker camera platform and subsequent quantitative analysis of the ICG signal were performed using a research version of a commercially available surgical real-time analysis software.

RESULTS

Using a high-frequency, low-dose bolus ICG regimen, fluorescence visualization and quantification in abdominal organs were successful in the stomach (3/3), ascending colon (1/3), rectum (2/3), and the spleen (3/3). ICG accumulation in the tissue over time did not affect the quantification process. Considerable variation in fluorescence signal was observed between organs and between the same organ in different subjects. Of the different camera conditions investigated, the highest signal was achieved when the camera was placed 7.5 cm from the target organ.

CONCLUSION

This proof-of-concept study finds that real-time continuous perfusion monitoring in different abdominal organs using ICG is feasible. However, the study also finds a large variation in fluorescence intensity between organs and between the same organ in different subjects while using a fixed weight-adjusted dosing regimen using the same camera setting and placement.

Timing of real-time indocyanine green fluorescence visualization for lymph node dissection during laparoscopic colon cancer surgery

PURPOSE

Although numerous studies have highlighted the potential value of indocyanine green (ICG) imaging in lymph node dissection of cancer surgery, its efficacy and optimal method remain to be clarified. This study aimed to investigate how lymphatic flow observation via ICG fluorescence could contribute to colon cancer surgery.

METHODS

From October 2018 to March 2021, a total of 56 patients with colon cancer who underwent laparoscopic complete mesocolic excision with intraoperative ICG imaging were analyzed. Lymphatic flow was examined at the following time points following ICG injection: within 5 min, 30-60 min, and over 60 min. We also evaluated the distribution of ICG fluorescence per each vascular pedicle.

RESULTS

Lymphatic flow was observed within 5 min following ICG injection in 6 cases (10.7%), and at 30-60 min following ICG injection in 43 cases (76.8%). ICG-stained vascular pedicles were variable especially in hepatic flexural, transverse, and splenic flexural colon cancer. Lymph node metastases were observed in 14 cases. Although metastatic lymph nodes were present only in the area along the ICG-stained vascular pedicles in 12 of the 14 cases, two patients exhibited lymph node metastasis in areas along the ICG-unstained vascular pedicles. ICG fluorescence was observed outside the standard range of lymph node dissection in 9 cases (20.9%: 9/43). Although addition of the proposed resection areas was made in 8 of these 9 cases, there was no pathologically positive lymph node.

CONCLUSION

Real-time ICG fluorescence imaging of lymph nodes may improve the performance of laparoscopic colon cancer surgery, although its oncological benefit is not yet clear.

The usefulness of indocyanine green fluorescence imaging for intestinal perfusion assessment of intracorporeal anastomosis in laparoscopic colon cancer surgery

PURPOSE

The purpose of this study was to clarify the usefulness of indocyanine green fluorescence imaging (ICG-FI) in the assessment of intestinal vascular perfusion in patients who receive intracorporeal anastomosis (IA) in colon cancer surgery.

METHODS

This was a single-center, retrospective study using propensity score matching. We compared the surgical outcomes of colon cancer patients who underwent laparoscopic colonic resection with IA or external anastomosis (EA) with the intraoperative evaluation of anastomotic perfusion using ICG-FI from January 2019 to July 2021. The detection rate of poor anastomotic perfusion by ICG-FI was examined.

RESULTS

A total of 223 patients were enrolled. After matching, 69 patients each were classified into the IA and EA groups. There were no significant differences in age, sex, body mass index, tumor localization, or progression between the two groups. The operation time was similar (172 min vs. 171 min, p = 0.62) and the amount of bleeding was significantly lower (0 ml vs. 2 ml, p = 0.0023) in the IA group. The complication rates (grade ≥ 2) of the two groups were similar (14.5% vs. 11.6%, p = 0.59). ICG-FI identified four patients (5.8%) with poor anastomotic perfusion in the IA group, but none in the EA group (p = 0.046). All four patients with poor perfusion in the IA group underwent additional resection; none of these patients developed postoperative complications.

CONCLUSION

Poor anastomotic perfusion was detected in 5.8% of cases who underwent laparoscopic colon cancer surgery with IA. ICG-FI is useful for evaluating anastomotic perfusion in IA in order to prevent AL.

Anastomotic perfusion assessment with indocyanine green in robot-assisted low-anterior resection, a multicenter study of interobserver variation

BACKGROUND

Securing sufficient blood perfusion to the anastomotic area after low-anterior resection is a crucial factor in preventing anastomotic leakage (AL). Intra-operative indocyanine green fluorescent imaging (ICG-FI) has been suggested as a tool to assess perfusion. However, knowledge of inter-observer variation among surgeons in the interpretation of ICG-FI is sparse. Our primary objective was to evaluate inter-observer variation among surgeons in the interpretation of bowel blood-perfusion assessed visually by ICG-FI. Our secondary objective was to compare the results both from the visual assessment of ICG and from computer-based quantitative analyses of ICG-FI between patients with and without the development of AL.

METHOD

A multicenter study, including patients undergoing robot-assisted low anterior resection with stapled anastomosis. ICG-FI was evaluated visually by the surgeon intra-operatively. Postoperatively, recorded videos were anonymized and exchanged between centers for inter-observer evaluation. Time to visibility (TTV), time to maximum visibility (TMV), and time to wash-out (TWO) were visually assessed. In addition, the ICG-FI video-recordings were analyzed using validated pixel analysis software to quantify blood perfusion.

RESULTS

Fifty-five patients were included, and five developed clinical AL. Bland-Altman plots (BA plots) demonstrated wide inter-observer variation for visually assessed fluorescence on all parameters (TTV, TMV, and TWO). Comparing leak-group with no-leak group, we found no significant differences for TTV: Hazard Ratio; HR = 0.82 (CI 0.32; 2.08), TMV: HR = 0.62 (CI 0.24; 1.59), or TWO: HR = 1.11 (CI 0.40; 3.11). In the quantitative pixel analysis, a lower slope of the fluorescence time-curve was found in patients with a subsequent leak: median 0.08 (0.07;0.10) compared with non-leak patients: median 0.13 (0.10;0.17) (p = 0.04).

CONCLUSION

The surgeon's visual assessment of the ICG-FI demonstrated wide inter-observer variation, there were no differences between patients with and without AL. However, quantitative pixel analysis showed a significant difference between groups.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04766060.

Deconstructing mastery in colorectal fluorescence angiography interpretation

INTRODUCTION

Indocyanine green fluorescence angiography (ICGFA) is commonly used in colorectal anastomotic practice with limited pre-training. Recent work has shown that there is considerable inconsistency in signal interpretation between surgeons with minimal or no experience versus those consciously invested in mastery of the technique. Here, we deconstruct the fluorescence signal patterns of expert-annotated surgical ICGFA videos to understand better their correlation and combine this with structured interviews to ascertain whether such interpretative capability is conscious or unconscious.

METHODS

For fluorescence signal analysis, expert-annotated ICGFA videos (n = 24) were quantitatively interrogated using a boutique intensity tracker (IBM Research) to generate signal time plots. Such fluorescence intensity data were examined for inter-observer correlation (Intraclass Correlation Coefficients, ICC) at specific curve milestones: the maximum fluorescence signal (Fmax), the times to both achieve this maximum (Tmax), as well as half this maximum (T1/2max) and the ratio between these (T1/2/Tmax). Formal tele-interview with contributing experts (n = 6) was conducted with the narrative transcripts being thematically mapped, plotted, and qualitatively analyzed.

RESULTS

Correlation by mathematical measures was excellent (ICC0.9-1.0) for Fmax, Tmax, and T1/2max (0.95, 0.938, and 0.925, respectively) and moderate (0.5-0.75) for T1/2/Tmax (0.729). While all experts narrated a deliberate viewing strategy, their specific dynamic signal appreciation differed in the manner of description.

CONCLUSION

Expert ICGFA users demonstrate high correlation in mathematical measures of their signal interpretation although do so tacitly. Computational quantification of expert behavior can help develop the necessary lexicon and training sets as well as computer vision methodology to better exploit ICGFA technology.

A Narrative Review of the Usefulness of Indocyanine Green Fluorescence Angiography for Perfusion Assessment in Colorectal Surgery

Anastomotic leakage is one of the most dreaded complications of colorectal surgery and is strongly associated with tissue perfusion. Indocyanine green fluorescence angiography (ICG-FA) using indocyanine green and near-infrared systems is an innovative technique that allows the visualization of anastomotic perfusion. Based on this information on tissue perfusion status, surgeons will be able to clearly identify colorectal segments with good blood flow for safer colorectal anastomosis. The results of several clinical trials indicate that ICG-FA may reduce the risk of AL in colorectal resection; however, the level of evidence is not high, as several other studies have failed to demonstrate a reduction in the risk of AL. Several large-scale RCTs are currently underway, and their results will determine whether ICG-FA is, indeed, useful. The major limitation of the current ICG-FA evaluation method, however, is that it is subjective and based on visual assessment by the surgeon. To complement this, the utility of objective evaluation methods for fluorescence using quantitative parameters is being investigated. Promising results have been reported from several clinical trials, but all trials are preliminary owing to their small sample size and lack of standardized protocols for quantitative evaluation. Therefore, appropriately standardized, high-quality, large-scale studies are warranted.

The effect of intracorporeal versus extracorporeal anastomosis in robotic right colectomy on perianastomotic perfusion: a substudy to a multicenter RCT

PURPOSE

Previous studies have shown that intracorporeal anastomosis (ICA) in minimally invasive right colectomy may improve postoperative recovery compared with extracorporeal anastomosis (ECA). It has been hypothesized that creating the anastomosis extracorporeally may cause mesenteric traction and compromised intestinal perfusion. The purpose of this study was to investigate the effect of either ICA or ECA on intestinal perfusion.

METHOD

This was a substudy to a multicenter, triple-blind randomized clinical trial comparing ICA with ECA in patients undergoing robotic right colectomy for colonic cancer. Videos from intraoperative Indocyanine Green (ICG) fluorescence imaging were analyzed with quantitative ICG perfusion assessment (q-ICG). q-ICG was performed by extracting perfusion metrics from a time-intensity curve generated from an image analysis software: F_MAX: maximal fluorescence intensity, T_MAX: time until maximal fluorescent signal, T_1/2MAX: time until half-maximal fluorescent signal, time ratio (T_1/2MAX/T_MAX) and slope.

RESULTS

A total of 68 patients (33 ICA and 35 ECA) were available for analysis. Demographics were similar between the groups, except for mean arterial blood pressure at the time of ICG infusion, which was significantly lower in the ICA group. We found a significantly steeper slope in the ICA group compared to the ECA group (6.3 vs. 4.7 AU/sec, P = .048). There were no significant differences in F_MAX, T_MAX, T_1/2MAX, and time ratio.

CONCLUSION

We found evidence of an improved intestinal perfusion following ICA compared with ECA. This finding may be related to patient outcomes and should be explored further in the future.

TRIAL REGISTRATION

CLINICALTRIALS

gov NCT03130166.

Utility and usability of laser speckle contrast imaging (LSCI) for displaying real-time tissue perfusion/blood flow in robot-assisted surgery (RAS): comparison to indocyanine green (ICG) and use in laparoscopic surgery

Background

Utility and usability of laser speckle contrast imaging (LSCI) in detecting real-time tissue perfusion in robot-assisted surgery (RAS) and laparoscopic surgery are not known. LSCI displays a color heatmap of real-time tissue blood flow by capturing the interference of coherent laser light on red blood cells. LSCI has advantages in perfusion visualization over indocyanine green imaging (ICG) including repeat use on demand, no need for dye, and no latency between injection and display. Herein, we report the first-in-human clinical comparison of a novel device combining proprietary LSCI processing and ICG for real-time perfusion assessment during RAS and laparoscopic surgeries.

Methods

ActivSight™ imaging module is integrated between a standard laparoscopic camera and scope, capable of detecting tissue blood flow via LSCI and ICG in laparoscopic surgery. From November 2020 to July 2021, we studied its use during elective robotic-assisted and laparoscopic cholecystectomies, colorectal, and bariatric surgeries (NCT# 04633512). For RAS, an ancillary laparoscope with ActivSight imaging module was used for LSCI/ICG visualization. We determined safety, usability, and utility of LSCI in RAS vs. laparoscopic surgery using end-user/surgeon human factor testing (Likert scale 1–5) and compared results with two-tailed t tests.

Results

67 patients were included in the study—40 (60%) RAS vs. 27 (40%) laparoscopic surgeries. Patient demographics were similar in both groups. No adverse events to patients and surgeons were observed in both laparoscopic and RAS groups. Use of an ancillary laparoscopic system for LSCI/ICG visualization had minimal impact on usability in RAS as evidenced by surgeon ratings of device usability (set-up 4.2/5 and form-factor 3.8/5). LSCI ability to detect perfusion (97.5% in RAS vs 100% in laparoscopic cases) was comparable in both RAS and laparoscopic cases.

Conclusions

LSCI demonstrates comparable utility and usability in detecting real-time tissue perfusion/blood flow in RAS and laparoscopic surgery.

Graphical abstract

Indocyanine green (ICG) fluorescence guide for the use and indications in general surgery: recommendations based on the descriptive review of the literature and the analysis of experience

Indocyanine Green is a fluorescent substance visible in near-infrared light. It is useful for the identification of anatomical structures (biliary tract, ureters, parathyroid, thoracic duct), the tissues vascularization (anastomosis in colorectal, esophageal, gastric, bariatric surgery, for plasties and flaps in abdominal wall surgery, liver resection, in strangulated hernias and in intestinal ischemia), for tumor identification (liver, pancreas, adrenal glands, implants of peritoneal carcinomatosis, retroperitoneal tumors and lymphomas) and sentinel node identification and lymphatic mapping in malignant tumors (stomach, breast, colon, rectum, esophagus and skin cancer). The evidence is very encouraging, although standardization of its use and randomized studies with higher number of patients are required to obtain definitive conclusions on its use in general surgery. The aim of this literature review is to provide a guide for the use of ICG fluorescence in general surgery procedures.

Does the level of inferior mesenteric artery ligation affect short-term and long-term outcomes of patients with sigmoid colon cancer or rectal cancer? A single-center retrospective study

Background

For sigmoid colon or rectal cancer, a definite consensus regarding the optimal level ligating the inferior mesenteric artery (IMA) has not been reached. We performed this study to determine whether the ligation level significantly affected short-term and long-term outcomes of patients with sigmoid colon or rectal cancer after curative laparoscopic surgery.

Methods

Medical records of patients with sigmoid colon or rectal cancer who had undergone curative laparoscopic surgery between January 2008 and December 2014 at the Department of Gastrointestinal Surgery, Guangdong Provincial Hospital of Traditional Chinese Medicine were reviewed. Then, the high tie group (HTG) was compared with the low tie group (LTG) in terms of short-term and long-term outcomes.

Results

Five-hundred ninety patients were included. No significant differences between two groups regarding baseline characteristics existed. HTG had a significantly higher risk of anastomotic fistula than LTG (21/283 vs 11/307, P = 0.040). Additionally, high ligation was proven by multivariate logistic regression analysis to be an independent factor for anastomotic fistula (P = 0.038, OR = 2.232, 95% CI: 1.047–4.758). Furthermore, LT resulted in better preserved urinary function. However, LTG was not significantly different from HTG regarding operative time (P = 0.075), blood transfusion (P = 1.000), estimated blood loss (P = 0.239), 30-day mortality (P = 1.000), ICU stay (P = 0.674), postoperative hospital stay (days) (P = 0.636), bowel obstruction (P = 0.659), ileus (P = 0.637), surgical site infection (SSI) (P = 0.121), number of retrieved lymph nodes (P = 0.501), and number of metastatic lymph nodes (P = 0.131). Subsequently, it was revealed that level of IMA ligation did not significantly influence overall survival (OS) (P = 0.474) and relapse-free survival (RFS) (P = 0.722). Additionally, it was revealed that ligation level did not significantly affect OS (P = 0.460) and RFS (P = 0.979) of patients with stage 1 cancer, which was also observed among patients with stage 2 or stage 3 cancer. Ultimately, ligation level was not an independent predictive factor for either OS or RFS.

Conclusions

HT resulted in a significantly higher incidence of anastomotic fistula and worse preservation of urinary function. Level of IMA ligation did not significantly affect long-term outcomes of patients with sigmoid colon or rectal cancer after curative laparoscopic surgery.

Assessment of blood perfusion quality in laparoscopic colorectal surgery by means of Machine Learning

An innovative algorithm to automatically assess blood perfusion quality of the intestinal sector in laparoscopic colorectal surgery is proposed. Traditionally, the uniformity of the brightness in indocyanine green-based fluorescence consists only in a qualitative, empirical evaluation, which heavily relies on the surgeon’s subjective assessment. As such, this leads to assessments that are strongly experience-dependent. To overcome this limitation, the proposed algorithm assesses the level and uniformity of indocyanine green used during laparoscopic surgery. The algorithm adopts a Feed Forward Neural Network receiving as input a feature vector based on the histogram of the green band of the input image. It is used to (i) acquire information related to perfusion during laparoscopic colorectal surgery, and (ii) support the surgeon in assessing objectively the outcome of the procedure. In particular, the algorithm provides an output that classifies the perfusion as adequate or inadequate. The algorithm was validated on videos captured during surgical procedures carried out at the University Hospital Federico II in Naples, Italy. The obtained results show a classification accuracy equal to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$99.9\%$$\end{document}99.9%, with a repeatability of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.9\%$$\end{document}1.9%. Finally, the real-time operation of the proposed algorithm was tested by analyzing the video streaming captured directly from an endoscope available in the OR.

Quantitative Analysis of Colonic Perfusion Using ICG Fluorescence Angiography and Its Consequences for Anastomotic Healing in a Rat Model

Forty-three rats were randomly assigned to the following four groups: non-ischemic group (Control Group), 1 cm-long ischemic group (Group 1), 2 cm-long ischemic group (Group 2), and 3 cm-long ischemic group (Group 3). The rates of AL were 0% (0/10) in the Control Group, 22.2% (2/9) in Group 1, 25% (2/8) in Group 2, and 50% (4/8) in Group 3. The bursting pressure of the Control Group was significantly higher than that of the other groups (p < 0.01). Regarding the pathological findings, the granulation thickness and the number of blood vessels at the anastomosed site were significantly higher in the Control Group than in Group 3 (p < 0.05). Receiver operating characteristics analysis revealed that Slope was the most significant predictor of AL, with an area under the curve of 0.861. When the cutoff value of Slope was 0.4, the sensitivity and specificity for the prediction of AL were 75% and 81.4%, respectively. Quantitative analysis of ICG fluorescence angiography could predict AL in a rat model.

Successful salvage of torsion testis by means of intraoperative indocyanine green fluorescence imaging

Background

Testicular torsion (TT) is common surgical emergency that requires early diagnosis and immediate intervention within 6 h since its onset to salvage the testis. However, the decision was made only by the surgeon’s experience whether it has to be resected or not. Recently, indocyanine green (ICG) has become an excellent tool to identify biliary and vascular anatomy, and assess perfusion abnormalities in tissues. In this case report, we successfully salvaged the twisted testis, since the testicular blood perfusion was confirmed by means of intraoperative ICG (IICG) fluorescence imaging.

Case presentation

A 14-year-old healthy male patient presented due to acute left testicular pain. The patient was diagnosed with TT and had immediate surgery. Macroscopically, the testis had stagnant blood flow and appeared to be dark colored. After manual detorsion, the testis remained cyanotic and with macroscopically poor blood flow. ICG angiography was performed under near-infrared light by laparoscopic camera to assess the perfusion of the affected testicle. An excellent ICG signal appeared after 45 s in the testis, and decision was made to be preserved. Therefore, left orchidopexy was performed to complete the operation. The patient had a good postoperative course and was discharged the day after surgery. Six months later, the testis did not show any shrinkage, and both sides of the testis showed the same size without any consequences.

Conclusion

The blood flow in the testis was visually confirmed during the IICG fluorescence method. ICG fluorescence imaging may become an effective alternative to evaluate whether a testis can be preserved following TT.

Experimental study of the quantification of indocyanine green fluorescence in ischemic and non-ischemic anastomoses, using the SERGREEN software program

Tissue ischemia is a key risk factor in anastomotic leak (AL). Indocyanine green (ICG) is widely used in colorectal surgery to define the segments with the best vascularization. In an experimental model, we present a new system for quantifying ICG fluorescence intensity, the SERGREEN software. Controlled experimental study with eight pigs. In the initial control stage, ICG fluorescence intensity was analyzed at the level of two anastomoses, in the right and in the left colon. Control images of the two segments were taken after ICG administration. The images were processed with the SERGREEN program. Then, in the experimental ischemia stage, the inferior mesenteric artery was sectioned at the level of the anastomosis of the left colon. Fifteen minutes after the section, sequential images of the two anastomoses were taken every 30 min for the following 2 h. At the control stage, the mean scores were 134.2 (95% CI 116.3–152.2) for the right colon and 147 (95% CI 134.7–159.3) for the left colon (p = 0.174) (Scale RGB—Red, Green, Blue). The right colon remained stable throughout the experiment. In the left colon, intensity fell by 47.9 points with respect to the pre-ischemia value (p < 0.01). After the first post-ischemia determination, the values of the ischemic left colon remained stable throughout the experiment. The relative decrease in ICG fluorescence intensity of the ischemic left colon was 32.6%. The SERGREEN program quantifies ICG fluorescence intensity in normal and ischemic situations and detects differences between them. A reduction in ICG fluorescence intensity of 32.6% or more was correlated with complete tissue ischemia.

The Role of Indocyanine Near-Infrared Fluorescence in Colorectal Surgery

Purposes

The aim of this study was to evaluate the importance of Indocyanine Green in control of anastomosis perfusion and on anastomotic leakage rates during laparoscopic and robotic colorectal procedures.

Methods

A retrospective review of patients who underwent elective minimally invasive surgery for colorectal cancer from 1 January 2018 to 31 December 2020 was performed. All patients underwent Near-Infrared Fluorescence-Indocyanine Green system in two moments: before performing the anastomosis and after completing the anastomotic procedure. Primary outcomes were the rate of intraoperative change in the surgical resection due to an inadequate vascularization and the rate of postoperative anastomotic leakage. Secondary outcomes were the postoperative complications, both medical and surgical (intra-abdominal bleeding, anastomotic leakage).

Results

Our analysis included 93 patients. Visible fluorescence was detected in 100% of the cases. In 7 patients (7.5%), the planned site of resection was changed due to inadequate perfusion. The mean extension of the surgical resection in these 7 patients was 2.2 ± 0.62. Anastomotic leakage occurred in 2 patients (2.1%). Other complications included 8 postoperative bleedings (8.6%) and 1 pulmonary thromboembolism.

Conclusions

The intraoperative use of Near-Infrared Fluorescence-Indocyanine Green in colorectal surgery is safe, feasible, and associated with a substantial reduction in postoperative anastomotic leakage rate.

Correlation between Colon Perfusion and Postoperative Fecal Output through a Transanal Drainage Tube during Laparoscopic Low Anterior Resection

In order to prevent anastomotic leakage (AL) following rectal surgery, various solutions—such as intraoperative indocyanine green (ICG) angiography and transanal drainage tubes (TDT)—have been proposed. This study investigated the relationship between intestinal perfusion and fecal volume through TDT in laparoscopic low anterior resection (LAR). A total of 59 rectal cancer patients who underwent laparoscopic LAR with both intraoperative ICG angiography and postoperative TDT placement were retrospectively analyzed. The relationship between intestinal perfusion and fecal volume through TDT was examined. Based on the ICG fluorescence, the transection site was shifted more proximally in 20 cases (33.9%). Symptomatic AL occurred in seven patients (11.8%). The AL rate of the patients whose daily fecal volume exceeded 100 mL/day in 2 or more days was significantly higher than that of those whose daily fecal volume exceeded it in 0 or 1 day (44.4% vs. 6.0%; p < 0.01). Univariate and multivariate analyses showed that the need for a proximal shift of the transection site was significantly associated with a high fecal volume. The quantitative analysis of ICG fluorescence indicated that Fmax (the fluorescence difference between the baseline and maximum) was significantly associated with fecal volume through TDT.

Combined indocyanine green and quantitative perfusion assessment with hyperspectral imaging during colorectal resections

Anastomotic insufficiencies still represent one of the most severe complications in colorectal surgery. Since tissue perfusion highly affects anastomotic healing, its objective assessment is an unmet clinical need. Indocyanine green-based fluorescence angiography (ICG-FA) and hyperspectral imaging (HSI) have received great interest in recent years but surgeons have to decide between both techniques. For the first time, two data processing pipelines capable of reconstructing an ICG-FA correlating signal from hyperspectral data were developed. Results were technically evaluated and compared to ground truth data obtained during colorectal resections. In 87% of 46 data sets, the reconstructed images resembled the ground truth data. The combined applicability of ICG-FA and HSI within one imaging system might provide supportive and complementary information about tissue vascularization, shorten surgery time, and reduce perioperative mortality.

The arrival time of indocyanine green in tissues can be a quantitative index because of its correlation with tissue oxygen saturation: A clinical pilot study

Indocyanine green (ICG) fluorescence angiography has recently been reported useful as a method for predicting intestinal blood flow and may reduce anastomotic leakage. However, the quantification method for ICG fluorescence angiography has not been established. We usually measure the tissue oxygen saturation (StO₂ ) in the intestinal tract via near-infrared spectroscopy, as it is able to measure the oxygen concentration accurately and immediately shows objective data. In this study, we propose that the time to reach the anastomotic site after intravenous ICG injection is an effective parameter for quantifying ICG fluorescence angiography from the comparison to the data of StO₂ in the intestinal tract.

Complications after bowel resection for inflammatory bowel disease associated cancer. A systematic literature review

INTRODUCTION

Inflammatory bowel disease (IBD) associated colorectal cancer represents the 1-2% of all patients affected by colorectal carcinoma, but it is frequent responsible for death in these patients. Aim of this systematic review was to report the complications after bowel resection in patients with IBD associated cancer.

EVIDENCE ACQUISITION

A systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis statement. The search was carried out in PubMed, Embase, Cochrane and Web of Science databases. A total of 54,084 articles were found. Of these 38,954 were eliminated because were duplicates between the searches. Of the remaining 15,130 articles, 14,888 were excluded after screening title and abstract.

EVIDENCE SYNTHESIS

Two-hundred-forty-two articles were fully analyzed, and 239 further articles were excluded. Finally, three articles were included for a total of 63 patients. Overall, 38 early postoperative complications (60.3%) were observed. Of these, anastomotic leakage occurred in 13 patients (20.6%). The indication for surgery was ulcerative colitis in 52 patients (82.5%), Crohn's disease in 8 patients (12.7%) and indeterminate colitis in 3 patients (4.8%). Intraoperative complications, readmission and postoperative mortality were not observed.

CONCLUSIONS

Complication rate after bowel resection for IBD associated cancer is not different from complication rate after colorectal surgery for other diseases. Given the high probability of developing a cancer and the time correlated occurrence of malignancy in IBD patients, it should be debated if a surgical resection should be performed as soon as dysplasia is detected in IBD patients or earlier in their life.

Multispectral Imaging Using Fluorescent Properties of Indocyanine Green and Methylene Blue in Colorectal Surgery-Initial Experience

Introduction: Image-guided surgery is becoming a new tool in colorectal surgery. Intraoperative visualisation of different structures using fluorophores helps during various steps of operations. In our report, we used two fluorophores—indocyanine green (ICG), and methylene blue (MB)—during different steps of colorectal surgery, using one camera system for two separate near-infrared wavelengths. Material and methods: Twelve patients who underwent complex open or laparoscopic colorectal surgeries were enrolled. Intravenous injections of MB and ICG at different time points were administered. Visualisation of intraoperative ureter position and fluorescent angiography for optimal anastomosis was performed. A retrospective analysis of patients treated in our departments during 2020 was performed, and data about ureter injury and anastomotic site complications were collected. Results: Intraoperative localisation of ureters with MB under fluorescent light was possible in 11 patients. The mean signal-to-background ratio was 1.58 ± 0.71. Fluorescent angiography before performing anastomosis using ICG was successful in all 12 patients, and none required a change in position of the planned colon resection for anastomosis. The median signal-to-background ratios was 1.25 (IQR: 1.22–1.89). Across both centres, iatrogenic injury of the ureter was found in 0.4% of cases, and complications associated with anastomosis was found in 5.5% of cases. Conclusions: Our study showed a substantial opportunity for using two different fluorophores in colorectal surgery, whereby the visualisation of one will not change the possible quantification analysis of the other. Using two separate dyes during one procedure may help in optimisation of the fluorescent properties of both dyes when using them for different applications. Visualisation of different structures by different fluorophores seems to be the future of image-guided surgery, and shows progress in optical technologies used in image-guided surgery.

Feasibility of quantitative analysis of colonic perfusion using indocyanine green to prevent anastomotic leak in colorectal surgery

BACKGROUND

The aim of this study was to quantify Fluorescence angiography with indocyanine green (ICG) in colorectal cancer anastomosis, determine influential factors in its temporary intensity and pattern, assessing the ability to predict the AL, and setting the cut-off levels to establish high- or low-risk groups.

METHODS

Retrospective analysis of prospectively managed database, including 70 patients who underwent elective surgery for colorectal cancer in which performing a primary anastomosis was in primary plan. In all of them, ICG fluorescence angiography was performed as usual clinical practice with VisionSense™ VS Iridium (Medtronic, Mansfield, MA, USA), in Elevision™ IR Platform (Medtronic, Mansfield, MA, USA). Parameters measured at real time or calculated were T₀, T_max, ∆T, F_max, %_pos, F_pos, and Slope.

RESULTS

70 patients were included, 69 anastomosis were performed and one end colostomy. Arterial hypertension demonstrated higher F_max, as well as the location of the anastomosis (the nearest to rectum, the most intensity detected). A statistical relationship was found between AL and the lower F_pos and Slope. The decision of changing the subjectively decided point of division did not demonstrate statistical difference on the further development of AL. All parameters were analyzed to detect the cut-off related with AL. Only in case of F_pos lower than 158.3 U and Slope lower than 13.1 U/s p-value were significant. The most valuable diagnostic parameter after risk stratification was the Negative Predictive Value.

CONCLUSION

Quantitative analysis of ICG fluorescence in colorectal surgery is safe and feasible to stratify risk of AL. Hypertension and location of anastomosis influence the intensity of fluorescence at the point of section. A change of division place should be considered to avoid AL related to vascular reasons when intensities of fluorescence at the point of section is lower than 169 U or slopes lower than 14.4 U/s.

Indocyanine green fluorescence angiography after full-thickness bowel resection for rectosigmoid endometriosis: A multicentric experience with quantitative analysis

OBJECTIVE

To evaluate effectiveness and reproducibility of qualitative and quantitative near-infrared indocyanine green (NIR-ICG) analyses as a tool for anastomotic perfusion assessment after full-thickness bowel resection for rectosigmoid endometriosis (RSE).

METHODS

Symptomatic women with RSE undergoing minimally invasive full-thickness surgical excision of RSE and NIR-ICG evaluation from November 2019 to July 2020 were included. Study outcomes were the accuracy of qualitative and quantitative NIR-ICG analyses in predicting bowel fistula and their reproducibility. NIR-ICG predictive accuracy was assessed by calculating sensitivity, specificity, and area under the curve on receiver operating characteristic curves with 95% confidence intervals (CI). NIR-ICG reproducibility was assessed through Cohen's k coefficient to determine interoperator agreement between two observers.

RESULTS

Of 33 patients, 2 (6%) developed bowel fistula. In predicting bowel fistula, qualitative and quantitative NIR-ICG evaluations showed sensitivity of 100% and 100%, specificity of 71% and 93%, and area under the curve of 0.86 (95% CI 0.67-1.00) and 0.96 (95% CI 0-1.00), respectively. Regarding interoperator agreement rate, it was reported as excellent for the qualitative analysis and very good for the quantitative analysis.

CONCLUSION

Qualitative and quantitative NIR-ICG evaluations might be effective and reproducible tools for anastomotic perfusion assessment after discoid or segmental resection for RSE. Quantitative evaluation might be even more effective than qualitative evaluation in predicting bowel fistula.

Evaluating the Effect of Intraoperative Near-Infrared Observation on Anastomotic Leakage After Stapled Side-to-Side Anastomosis in Colon Cancer Surgery Using Propensity Score Matching

BACKGROUND

Recent studies have clarified that near-infrared observation using indocyanine green has the advantage of evaluating perfusion of the anastomotic site, especially in rectal cancer surgery, resulting in a reduction in anastomotic leak.

OBJECTIVE

The aim of this study was to evaluate the efficacy of near-infrared observation for reducing the anastomotic leak after stapled side-to-side anastomosis in colon cancer surgery.

DESIGN

This was a retrospective propensity score case-matched study.

SETTINGS

The study was conducted at 3 institutions in the Yokohama Clinical Oncology Group.

PATIENTS

From January 2011 to December 2019, patients who underwent colon cancer surgery with stapled side-to-side anastomosis were included.

MAIN OUTCOME MEASURES

The main outcome was the percentage of anastomotic leak within 30 days after surgery.

RESULTS

A total of 1034 patients were collected. There were 532 patients who underwent near-infrared observation and 502 who did not. A total of 370 patients were matched to the near-infrared and non-near-infrared groups. In the near-infrared group, 12 patients (3.2%) were judged to have poor perfusion (4 patients) and no perfusion (8 patients), so the planned transection point was changed. There were no cases of anastomotic leak among these 12 patients. The anastomotic leak rates were 3.5% (13/370) in the non-near-infrared group and 0.8% (3/370) in the near-infrared group. The anastomotic leak and reoperation rates were significantly lower in the near-infrared group than in the non-near-infrared group (OR, 0.224; 95% CI, 0.063-0.794, p = 0.001; OR, 0.348; 95% CI, 0.124-0.977, p = 0.036).

LIMITATIONS

Although we reduced selection bias by performing propensity score matching, this was a retrospective study and was not randomized.

CONCLUSION

This large-scale case-matched study showed that assessing perfusion by near-infrared observation significantly reduced the anastomotic leak and reoperation rates after stapled side-to-side anastomosis in colon cancer surgery and may be better suited to colo-colonic anastomosis. Video Abstract at http://links.lww.com/DCR/B513.Japanese Clinical Trials Registry: UMIN-CTR000039977.

EVALUACIN DEL EFECTO DE LA OBSERVACIN INTRAOPERATORIA CON INFRARROJO CERCANO SOBRE LA FUGA ANASTOMTICA DESPUS DE UNA ANASTOMOSIS LATEROLATERAL CON ENGRAPADORA EN LA CIRUGA DE CNCER DE COLON MEDIANTE EL EMPAREJAMIENTO POR PUNTAJES DE PROPENSIN

ANTECEDENTES:Estudios recientes han aclarado que la observación con infrarrojo cercano con verde de indocianina tiene la ventaja de evaluar la perfusión del sitio anastomótico, especialmente en la cirugía de cáncer de recto, lo que resulta en una reducción de la fuga anastomótica.OBJETIVO:El objetivo de este estudio fue evaluar la eficacia de la observación con infrarrojo cercano para reducir la fuga anastomótica después de una anastomosis latero-lateral con engrapadora en la cirugía de cáncer de colon.DISEÑO:Este fue un estudio retrospectivo emparejado con puntaje de propensión.AJUSTE:El estudio se llevó a cabo en tres instituciones del Grupo de Oncología Clínica de Yokohama.PACIENTES:Desde enero de 2011 hasta diciembre de 2019, se incluyeron pacientes que se sometieron a cirugía de cáncer de colon con anastomosis latero-lateral con engrapadora.PRINCIPALES MEDIDAS DE RESULTADO:El resultado principal fue el porcentaje de fuga anastomótica dentro de los 30 días posteriores a la cirugía.RESULTADOS:Se recogió un total de 1034 pacientes. Hubo 532 pacientes que se sometieron a observación con infrarrojo cercano y 502 que no. Un total de 370 pacientes fueron emparejados con los grupos de infrarrojo cercano y no infrarrojo cercano. En el grupo de infrarrojo cercano, se consideró que 12 casos (3,2%) tenían mala perfusión (4 casos) y ninguna perfusión (8 casos), por lo que se cambió el punto de transección planificado. No hubo casos de fuga anastomótica entre estos 12 casos. Las tasas de fuga anastomótica fueron del 3,5% (13/370) en el grupo sin infrarrojo cercano y del 0,8% (3/370) en el grupo con infrarrojo cercano. Las tasas de fuga anastomótica y de reintervención fueron significativamente menores en el grupo con infrarrojo cercano que en el grupo sin infrarrojo cercano (razón de posibilidades 0,224, intervalo de confianza del 95% 0,063-0,794, p = 0,001; razón de posibilidades 0,348, intervalo de confianza del 95% 0,124 -0,977, p = 0,036, respectivamente).LIMITACIONES:Aunque se redujo el sesgo de selección al realizar el emparejamiento por puntaje de propensión, este fue un estudio retrospectivo y no fue aleatorio.CONCLUSIÓN:Este estudio de casos emparejados a gran escala demostró que la evaluación de la perfusión mediante la observación con infrarrojo cercano redujo significativamente la fuga anastomótica y las tasas de reintervención después de la anastomosis latero-lateral con engrapadora en la cirugía de cáncer de colon y puede ser más adecuada para la anastomosis colo-colónica. Consulte Video Resumen en http://links.lww.com/DCR/B513.Registro japonés de ensayos clínicos: UMIN-CTR000039977.

Indocyanine green: An old drug with novel applications

Indocyanine green (ICG), a US Food and Drug Administration-approved fluorescent compound, has been on the medical stage for more than 60 years. Current uses include hepatic function evaluation before surgical procedure and fundus evaluation. The large safety margin and near-infrared fluorescent optical advantage of the drug have proved useful in several clinical trials of intraoperative systems for tumor removal. Several nanoparticle-sized formulations for thermal ablation and photodynamic therapy have also been evaluated in animal experiments. Studies have attempted to manipulate ICG as a reporter fluorophore with initial success. In this article, we reviewed ICG's histological applications, chemical and physical properties, current clinical applications, ongoing clinical trials, and biomedical studies and prospects. We believe that ICG could be used with novel biotechnological techniques, such as fluorescent endoscopy and photoacoustic equipment, in a range of biomedical fields.

Development of Surgical and Visualization Procedures to Analyze Vasculatures by Mouse Tail Edema Model

Background

Because of the high frequency of chronic edema formation in the current “aged” society, analyses and detailed observation of post-surgical edema are getting more required. Post-surgical examination of the dynamic vasculature including L.V. (Lymphatic Vasculature) to monitor edema formation has not been efficiently performed. Hence, procedures for investigating such vasculature are essential. By inserting transparent sheet into the cutaneous layer of mouse tails as a novel surgery model (theTailEdema bySilicone sheet mediatedTransparency protocol; TEST), the novel procedures are introduced and analyzed by series of histological analyses including video-based L.V. observation and 3D histological reconstruction of vasculatures in mouse tails.

Results

The dynamic generation of post-surgical main and fine (neo) L.V. connective structure during the edematous recovery process was visualized by series of studies with a novel surgery model. Snapshot images taken from live binocular image recording for TEST samples suggested the presence of main and elongating fine (neo) L.V. structure. After the ligation of L.V., the enlargement of main L.V. was confirmed. In the case of light sheet fluorescence microscopy (LSFM) observation, such L.V. connections were also suggested by using transparent 3D samples. Finally, the generation of neo blood vessels particularly in the region adjacent to the silicone sheet and the operated boundary region was suggested in 3D reconstruction images. However, direct detection of elongating fine (neo) L.V. was not suitable for analysis by such LSFM and 3D reconstruction procedures. Thus, such methods utilizing fixed tissues are appropriate for general observation for the operated region including of L.V.

Conclusions

The current surgical procedures and analysis on the post-surgical status are the first case to observe vasculatures in vivo with a transparent sheet. Systematic analyses including the FITC-dextran mediated snap shot images observation suggest the elongation of fine (neo) lymphatic vasculature. Post-surgical analyses including LSFM and 3D histological structural reconstruction, are suitable to reveal the fixed structures of blood and lymphatic vessels formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12575-021-00159-3.