Defining indocyanine green fluorescence to assess anastomotic perfusion during gastrointestinal surgery: systematic review

Does Indocyanine Green Utilization during Esophagectomy Prevent Anastomotic Leaks? Systematic Review and Meta-Analysis

Background: Indocyanine Green (ICG) is a promising technique for the assessment of gastric conduit and anastomosis perfusion during esophagectomy. ICG integration may be helpful in minimizing the risk of anastomotic leak (AL). Literature evidence is sparse, while the real effect of ICG assessment on AL minimization remains unsolved. The aim of this systematic review and meta-analysis was to compare short-term outcomes between ICG-guided and non-ICG-guided (nICG) esophagogastric anastomosis during esophagectomy for cancer. Materials and Methods: PubMed, MEDLINE, Scopus, Web of Science, Cochrane Central Library, and ClinicalTrials.gov were queried up to 25 April 2024. Studies that reported short-term outcomes for ICG versus non-ICG-guided (nICG) anastomosis in patients undergoing esophagectomy were considered. Primary outcome was AL. Risk ratio (RR) and standardized mean difference (SMD) were utilized as effect size measures, whereas to assess relative inference we used 95% confidence intervals (95% CI). Results: Overall, 1399 patients (11 observational studies) were included. Overall, 576 (41.2%) underwent ICG gastric conduit assessment. The patients' ages ranged from 22 to 91 years, with 73% being male. The cumulative incidence of AL was 10.4% for ICG and 15.4% for nICG. Compared to nICG, ICG utilization was related to a reduced risk for postoperative AL (RR 0.48; 95% CI 0.23-0.99; p = 0.05). No differences were found in terms of pulmonary complications (RR 0.83), operative time (SMD -0.47), hospital length of stay (SMD -0.16), or 90-day mortality (RR 1.70). Conclusions: Our study seems to indicate a potential impact of ICG in reducing post-esophagectomy AL. However, because of limitations in the design of the included studies, allocation/reporting bias, variable definitions of AL, and heterogeneity in ICG use, caution is required to avoid potential overestimation of the ICG effect.

Late-onset lethal complication of non-surgically managed massive gastric conduit necrosis after esophagectomy: a case report

BACKGROUND

Gastric conduit necrosis (GCN) after esophagectomy is a serious complication that can prove fatal. Herein, we report a rare case of GCN with a severe course that improved with conservative treatment.

CASE PRESENTATION

We present the case of a 78-year-old male patient who underwent an Ivor Lewis esophagectomy and developed a massive GCN. The patient was critically ill in the initial phase but recovered quickly; he also had a ruptured gallbladder and a bleeding jejunal ulcer. On the 22nd postoperative day, massive GCN was revealed on endoscopy. Considering the recovery course, careful observation with a decompressing nasal gastric tube was the treatment of choice. The GCN was managed successfully, having been completely replaced by fine mucosa within 9 months postoperatively. The patient completed his follow-up visit 5 years after surgery without any evident disease recurrence. Five and a half years after the surgery, the patient presented with progressive weakness and deterioration of renal function. Gastrointestinal endoscopy revealed a large ulcer at the anastomotic site. Three months later, computed tomography revealed a markedly thin esophageal wall, accompanied by adjacent lung consolidation. An esophagopulmonary fistula was diagnosed; surgery was not considered, owing to the patient's age and markedly deteriorating performance status. He died 2013 days after the diagnosis.

CONCLUSIONS

Massive GCN after esophagectomy often requires emergency surgery to remove the necrotic conduit. However, this report suggests that a conservative approach can save lives and preserve the gastric conduit in these cases, thereby augmenting the quality of life.

NIR-II light in clinical oncology: opportunities and challenges

Novel strategies utilizing light in the second near-infrared region (NIR-II; 900-1,880 nm wavelengths) offer the potential to visualize and treat solid tumours with enhanced precision. Over the past few decades, numerous techniques leveraging NIR-II light have been developed with the aim of precisely eliminating tumours while maximally preserving organ function. During cancer surgery, NIR-II optical imaging enables the visualization of clinically occult lesions and surrounding vital structures with increased sensitivity and resolution, thereby enhancing surgical quality and improving patient prognosis. Furthermore, the use of NIR-II light promises to improve cancer phototherapy by enabling the selective delivery of increased therapeutic energy to tissues at greater depths. Initial clinical studies of NIR-II-based imaging and phototherapy have indicated impressive potential to decrease cancer recurrence, reduce complications and prolong survival. Despite the encouraging results achieved, clinical translation of innovative NIR-II techniques remains challenging and inefficient; multidisciplinary cooperation is necessary to bridge the gap between preclinical research and clinical practice, and thus accelerate the translation of technical advances into clinical benefits. In this Review, we summarize the available clinical data on NIR-II-based imaging and phototherapy, demonstrating the feasibility and utility of integrating these technologies into the treatment of cancer. We also introduce emerging NIR-II-based approaches with substantial potential to further enhance patient outcomes, while also highlighting the challenges associated with imminent clinical studies of these modalities.

Current applications of indocyanine green (ICG) in abdominal, gynecologic and urologic surgery: a meta-review and quality analysis with use of the AMSTAR 2 instrument

BACKGROUND

Indocyanine green (ICG) is an injectable fluorochrome that has recently gained popularity as a means of assisting intraoperative visualization during laparoscopic and robotic surgery. Many systematic reviews and meta-analyses have been published. We conducted a meta-review to synthesize the findings of these studies.

METHODS

PubMed and Embase were searched to identify systematic reviews and meta-analyses coping with the uses of ICG in abdominal operations, including Metabolic Bariatric Surgery, Cholecystectomy, Colorectal, Esophageal, Gastric, Hepato-Pancreato-Biliary, Obstetrics and Gynecology (OG), Pediatric Surgery, Surgical Oncology, Urology, (abdominal) Vascular Surgery, Adrenal and Splenic Surgery, and Interdisciplinary tasks, until September 2023. We submitted the retrieved meta-analyses to qualitative analysis based on the AMSTAR 2 instrument.

RESULTS

We identified 116 studies, 41 systematic reviews (SRs) and 75 meta-analyses (MAs), spanning 2013-2023. The most thoroughly investigated (sub)specialties were Colorectal (6 SRs, 25 MAs), OG (9 SRs, 15 MAs), and HPB (4 SRs, 12 MAs). Interestingly, there was high heterogeneity regarding the administered ICG doses, routes, and timing. The use of ICG offered a clear benefit regarding anastomotic leak prevention, particularly after colorectal and esophageal surgery. There was no clear benefit regarding sentinel node detection after OG. According to the AMSTAR 2 tool, most meta-analyses ranked as "critically low" (34.7%) or "low" (58.7%) quality. There were only five meta-analyses (6.7%) that qualified as "moderate" quality, whereas there were no "high" quality reviews.

CONCLUSIONS

Regardless of the abundance of pertinent literature and reviews, surgeons should be cautious when interpreting their results on ICG use in abdominal surgery. Future reviews should focus on ensuring methodological vigor; establishing clear protocols of ICG dose, route of administration, and timing; and improving reporting quality. Other sources of data (e.g., registries) and novel methods of data analysis (e.g., machine learning) might also contribute to an enhanced role of ICG as a decision-making tool in surgery.

Indocyanin Green Fluorescence Evaluation of Colonic Perfusion During Elective Open Abdominal Aortic Aneurysm Repair

OBJECTIVES

Colonic ischaemia is a rare but devastating complication of open aortic aneurysm repair and is associated with high morbidity and a mortality of up to 50%. The aim of this study was to determine the safety and effectiveness of using indocyanin green florescence (ICG) to interrogate colonic perfusion intra-operatively.

DESIGN

Prospective observational study.

METHODS

All elective open abdominal aneurysm repairs over a 6 month period underwent colonic perfusion interrogation with ICG according to a pre-defined protocol. Patient demographics and imaging findings were recorded prior to surgery. ICG was given just prior to laparotomy closure. Time to florescence was measured from the start of IV administration to surgeon defined maximal florescence of the sigmoid colon.

RESULTS

Ten patients fulfilled the inclusion criteria. All patients were male with an average age of 69.7 years. Inferior mesenteric artery reimplantation was performed in 5 patients. Median colonic fluorescence time was 58 s. No complications related to ICG were identified. A single patient had clinical concern of colonic ischaemia and delayed perfusion (>3 min) on ICG; colorectal opinion advised not for immediate resection. At relook laparotomy, ischaemic colon at the area of demarcation was noted and a Hartmann's procedure was performed. No other patients had delayed perfusion and no further episodes of colonic ischaemia were noted. IMA reimplantation did not show statistical difference in colonic ICG time (P = .81, 95% CI -1.98 to 2.45). There was no statistical difference between operating times between the cohort and all repairs performed 6 months before the data collection (P = .59, 95% CI -.73 to 1.24).

CONCLUSION

In this pilot study ICG appears to be a safe and useful adjunct in objective assessment of colonic perfusion during open AAA repair. Further research is required to fully determine its role in this cohort of patients.

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 pancreas stump perfusion assessment during pancreaticoduodenectomy: A systematic scoping review

BACKGROUND

Post-operative pancreatic fistula (POPF) is the primary cause of morbidity following pancreaticoduodenectomy. Rates of POPF have remained high despite well known risk factors. The theory that hypoperfusion of the pancreatic stump leads to anastomotic failure has recently gained interest.

AIM

To define the published literature with regards to intraoperative pancreas perfusion assessment and its correlation with POPF.

METHODS

A systematic search of available literature was performed in November 2022. Data extracted included study characteristics, method of assessment of pancreas stump perfusion, POPF and other post-pancreatic surgery specific complications.

RESULTS

Five eligible studies comprised two prospective non-randomised studies and three case reports, total 156 patients. Four studies used indocyanine green fluorescence angiography to assess the pancreatic stump, with the remaining study assessing pancreas perfusion by visual inspection of arterial bleeding of the pancreatic stump. There was significant heterogeneity in the definition of POPF. Studies had a combined POPF rate of 12%; intraoperative perfusion assessment revealed hypoperfusion was present in 39% of patients who developed POPF. The rate of POPF was 11% in patients with no evidence of hypoperfusion and 13% in those with evidence of hypoperfusion, suggesting that not all hypoperfusion gives rise to POPF and further analysis is required to analyse if there is a clinically relevant cut off. Significant variance in practice was seen in the pancreatic stump management once hypoperfusion was identified.

CONCLUSION

The current published evidence around pancreas perfusion during pancreaticoduodenectomy is of poor quality. It does not support a causative link between hypoperfusion and POPF. Further well-designed prospective studies are required to investigate this.

Indocyanine Green (ICG) and Colorectal Surgery: A Literature Review on Qualitative and Quantitative Methods of Usage

Background: Due to its many benefits, indocyanine green (ICG) has gained progressive popularity in operating rooms (ORs) globally. This literature review examines its qualitative and quantitative usage in surgical treatment. Method: Relevant terms were searched in five international databases (1. Pubmed, 2. Sciencedirect, 3. Scopus, 4. Oxfordjournals, 5. Reaxys) for a comprehensive literature review. The main benefits of using ICG in colorectal surgery are: intraoperative fluorescence angiography; fluorescence-guided lymph node involvement detection and the sentinel technique; the fluorescent emphasis of a minute liver tumour, counting just 200 tumour cells; facilitation of fistula diagnosis; and tumour tattooing. This methodology can also be used with quantitative characteristics such as maximum intensity, relative maximum intensity, and in-flow parameters such as time-to-peak, slope, and t1/2max. This article concludes that fluorescence surgery with ICG and near-infrared (NIR) light is a relatively new technology that improves anatomical and functional information, allowing more comprehensive and safer tumour removal and the preservation of important structures.

Indocyanine green angiography for lower incidence of anastomotic leakage after transanal total mesorectal excision: a propensity score-matched cohort study

Background

Anastomotic leakage (AL) is the most serious complication that can arise during colorectal surgery. Indocyanine green (ICG) angiography offers an intraoperative assessment of colonic vascular perfusion in real time. We aimed to assess ICG's effects on the AL rate in patients who have undergone transanal total mesorectal excision (TaTME) for rectal cancer.

Methods

This retrospective cohort study was conducted at our center from October 2018 to March 2022 to analyze the clinical data of patients with rectal cancer who have undergone TaTME after propensity score matching (PSM). The primary outcome was the proximal colonic transection line modification and clinical AL rate.

Results

A total of 143 patients in the non-ICG group and 143 patients in the ICG group were included after PSM. The proximal colonic transection line of seven patients in the non-ICG group was modified, while 18 were in the ICG group (4.9% vs. 12.5%, p = 0.023). Twenty-three patients (16.1%) in the non-ICG group and five patients (3.5%) in the ICG group were diagnosed with AL (p < 0.001). The ICG group had a less hospital readmission rate than the non-ICG group (0.7% vs. 7.7%, p = 0.003). The between-group differences in basic line and other outcomes were not significant.

Conclusions

ICG angiography is a safe and feasible method to help surgeons identify potentially poor colonic vascular perfusion and modify the proximal colonic transection line, resulting in a significant reduction in AL and hospital readmission rates.

Perfusion assessment by fluorescence time curves in esophagectomy with gastric conduit reconstruction: a prospective clinical study

BACKGROUND

Intraoperative perfusion assessment with indocyanine green fluorescence angiography (ICG-FA) may reduce postoperative anastomotic leakage rates after esophagectomy with gastric conduit reconstruction. This study evaluated quantitative parameters derived from fluorescence time curves to determine a threshold for adequate perfusion and predict postoperative anastomotic complications.

METHODS

This prospective cohort study included consecutive patients who underwent FA-guided esophagectomy with gastric conduit reconstruction between August 2020 and February 2022. After intravenous bolus injection of 0.05-mg/kg ICG, fluorescence intensity was registered over time by PINPOINT camera (Stryker, USA). Fluorescent angiograms were quantitatively analyzed at a region of interest of 1 cm diameter at the anastomotic site on the conduit using tailor-made software. Extracted fluorescence parameters were both inflow (T₀, T_max, F_max, slope, Time-to-peak) as outflow parameters (T_90% and T_80%). Anastomotic complications including anastomotic leakage (AL) and strictures were documented. Fluorescence parameters in patients with AL were compared to those without AL.

RESULTS

One hundred and three patients (81 male, 65.7 ± 9.9 years) were included, the majority of whom (88%) underwent an Ivor Lewis procedure. AL occurred in 19% of patients (n = 20/103). Both time to peak as T_max were significantly longer for the AL group in comparison to the non-AL group (39 s vs. 26 s, p = 0.04 and 65 vs. 51 s, p = 0.03, respectively). Slope was 1.0 (IQR 0.3-2.5) and 1.7 (IQR 1.0-3.0) for the AL and non-AL group (p = 0.11). Outflow was longer in the AL group, although not significantly, T_90% 30 versus 15 s, respectively, p = 0.20). Univariate analysis indicated that T_max might be predictive for AL, although not reaching significance (p = 0.10, area under the curve 0.71) and a cut-off value of 97 s was derived, with a specificity of 92%.

CONCLUSION

This study demonstrated quantitative parameters and identified a fluorescent threshold which could be used for intraoperative decision-making and to identify high-risk patients for anastomotic leakage during esophagectomy with gastric conduit reconstruction. A significant predictive value remains to be determined in future studies.

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.

Quantitative perfusion assessment using indocyanine green during surgery - current applications and recommendations for future use

PURPOSE

Incorrect assessment of tissue perfusion carries a significant risk of complications in surgery. The use of near-infrared (NIR) fluorescence imaging with Indocyanine Green (ICG) presents a possible solution. However, only through quantification of the fluorescence signal can an objective and reproducible evaluation of tissue perfusion be obtained. This narrative review aims to provide an overview of the available quantification methods for perfusion assessment using ICG NIR fluorescence imaging and to present an overview of current clinically utilized software implementations.

METHODS

PubMed was searched for clinical studies on the quantification of ICG NIR fluorescence imaging to assess tissue perfusion. Data on the utilized camera systems and performed methods of quantification were collected.

RESULTS

Eleven software programs for quantifying tissue perfusion using ICG NIR fluorescence imaging were identified. Five of the 11 programs have been described in three or more clinical studies, including Flow® 800, ROIs Software, IC Calc, SPY-Q™, and the Quest Research Framework®. In addition, applying normalization to fluorescence intensity analysis was described for two software programs.

CONCLUSION

Several systems or software solutions provide a quantification of ICG fluorescence; however, intraoperative applications are scarce and quantification methods vary abundantly. In the widespread search for reliable quantification of perfusion with ICG NIR fluorescence imaging, standardization of quantification methods and data acquisition is essential.

Indocyanine green fluorescence in robot-assisted minimally invasive esophagectomy with intrathoracic anastomosis: a prospective study

Indocyanine green fluorescence angiography (ICG-FA) allows for real-time intraoperative assessment of the perfusion of the gastric conduit during esophagectomy. The aim of this study was to investigate the effect of the implementation of ICG-FA during robot-assisted minimally invasive esophagectomy (RAMIE) with an intrathoracic anastomosis. In this prospective cohort study, a standardized protocol for ICG-FA was implemented in a high-volume center in December 2018. All consecutive patients who underwent RAMIE with an intrathoracic anastomosis were included. The primary outcome was whether the initial chosen site for the anastomosis on the gastric conduit was changed based on ICG-FA findings. In addition, ICG-FA was quantified based on the procedural videos. Out of the 63 included patients, the planned location of the anastomosis was changed in 9 (14%) patients, based on ICG-FA. The median time to maximum intensity at the base of the gastric conduit was shorter (25 s; range 13-49) compared to tip (34 s; range 12-83). In patients with anastomotic leakage, the median time to reach the FImax at the tip was 56 s (range 30-83) compared to 34 s (range 12-66) in patients without anastomotic leakage (p = 0.320). The use of ICG-FA resulted in an adaptation of the anastomotic site in nine (14%) patients during RAMIE with intrathoracic anastomosis. The quantification of ICG-FA showed that the gastric conduit reaches it maximum intensity in a base-to-tip direction. Perfusion of the entire gastric conduit was worse for patients with anastomotic leakage, although not statistically different.

Feasibility of Novel Software-Based Perfusion Indicators for the Ileal J-Pouch-On the Path towards Objective and Quantifiable Intraoperative Perfusion Assessment with Indocyanine Green Near-Infrared Fluorescence

BACKGROUND

In restorative proctocolectomy with ileal J-pouch, perfusion assessment is vital to prevent complications such as anastomotic leak (AL). Indocyanine green near-infrared fluorescence (ICG-NIRF) is gaining popularity, while its interpretation and relevance remain subjective. This study aimed to evaluate a standardized ICG-NIRF imaging protocol combined with a novel, software-based assessment to detect areas of impaired perfusion and a possible correlation with AL of the pouch.

METHODS

In this prospective study, patients undergoing ileal J-pouch for ulcerative colitis at an inflammatory bowel disease (IBD) referral center were included. Intraoperatively, strictly standardized ICG-NIRF visualization was performed and video-recorded. Postoperatively, a specific software was utilized to determine the change in fluorescence intensity per second (i/s) for systematic regions of interest, generating perfusion-time curves and a pixel-to-pixel map. These were analysed in detail and correlated with clinical outcome (primary end point: AL within 30 days; clearly defined and screened for by pouchoscopy).

RESULTS

Four out of 18 included patients developed AL of the ileal pouch-anal anastomosis (IPAA). In the AL group, the perfusion curves on the area adjacent to the IPAA (pouch apex) displayed considerably lower ingress/inflow (median = 1.7; range = 8.5; interquartile-range = 3.8 i/s) and egress/outflow (median = -0.1; range = 0.7; interquartile-range = 0.5 i/s) values than in the non-AL group (ingress: median = 4.3; range = 10.3; interquartile-range = 4.0 i/s); egress: median = (-1.1); range = 3.9; interquartile range = 1.0 i/s). This was confirmed by further novel parameters of pouch perfusion (maximum ingress; maximum egress) and pixel-to-pixel analysis.

CONCLUSIONS

This study presents the feasibility of a novel methodology to precisely assess pouch perfusion with ICG-NIRF, identifying comparable, quantifiable, and objective parameters to potentially detect perfusion-associated complications in surgery in real-time.

In vivo real-time assessment of the anastomotic blood supply in colorectal surgery using confocal laser endomicroscopy in an anastomotic model

BACKGROUND AND STUDY AIMS

Anastomotic ischemia can affect healing and eventually lead to anastomotic leakage, and confocal laser endomicroscopy (CLE) can offer detailed observations at the subcellular level. We aimed to evaluate the anastomotic microcirculation in different anastomotic perfusion models using CLE.

METHODS

Anastomotic perfusion models were established using twelve rabbits distributed into two groups: group A (good perfusion, n = 6) and group B (poor perfusion, n = 6). Afterward, intraoperative detection of anastomotic perfusion was carried out using CLE, and quantitative analysis of blood cells was performed. Rabbits that satisfied the criteria underwent a second exploratory operation and specimens were stained by hematoxylin and eosin.

RESULTS

Enhanced with fluorescein sodium, capillaries were obviously highlighted in group A, while few capillaries were viewed in group B. Delayed development of fluorescence occurred in group B. The average flow of blood cells was 37.0 ± 5.93 per minute in group A and 6.33 ± 2.16 per minute in group B (p < 0.001). In addition, during the second exploratory surgery, rabbits with inadequate anastomotic perfusion exhibited more serious intestinal adhesion and ischemia. Anastomotic leakage and abdominal infection occurred in all rabbits in group B.

CONCLUSION

CLE can realize real-time imaging of the anastomotic microcirculation and is a feasible technique for performing intraoperative evaluation in different anastomotic perfusion situations. This animal experiment provides the groundwork for future in vivo research in humans.

Quantification of gastric tube perfusion following esophagectomy using fluorescence imaging with indocyanine green

INTRODUCTION

Anastomotic leakage (AL) remains a prevalent and life-threatening complication after esophagectomy. Gastric tube perfusion assessment using indocyanine green fluorescence imaging (ICG-FI) has been published in several studies and appears to be a promising tool to reduce AL rates by changing the surgical approach, namely by an intraoperative evaluation of the anastomosis localization.

METHODS

In this study, gastric tube perfusion was quantified by using ICG-FI in 20 high-risk patients undergoing esophagectomy. From a time-dependent fluorescence intensity curve, the following three parameters were evaluated: slope of fluorescence intensity (SFI), background subtracted peak fluorescence intensity (BSFI), and time to slope (TTS).

RESULTS

The values between pyloric region and tip showed a similar downward trend and SFI and BSFI significantly correlated with the distance to the pyloric region. SFI and BSFI were significantly decreased at the tip of the gastric tube. The placement of anastomosis in an area with homogenous fluorescence pattern was correlated with no AL in 92.9% of cases. An inhomogeneous fluorescence pattern at anastomotic site was a risk factor for the occurrence of an AL (p < 0.05). Reduction of perfusion up to 32% using SFI and up to 23% using BSFI was not associated with AL.

CONCLUSION

ICG-FI can be used to quantify the gastric tube perfusion by calculating SFI, BSFI, and TTS. The anastomosis should be created in areas with homogeneous fluorescence pattern. A reduction in blood flow of up to 32% can be accepted without causing an increased rate of insufficiency.

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.

Indocyanine green (ICG) fluorescence imaging for prevention of anastomotic leak in totally minimally invasive Ivor Lewis esophagectomy: a systematic review and meta-analysis

BACKGROUND

Indocyanine green (ICG) fluorescence imaging is an emerging technology that might help decreasing anastomotic leakage (AL) rates. The aim of this study was to determine the usefulness of ICG fluorescence imaging for the prevention of AL after minimally invasive esophagectomy with intrathoracic anastomosis.

METHODS

A systematic literature review of the MEDLINE and Cochrane databases was performed to identify all articles on totally minimally invasive Ivor Lewis esophagectomy. Studies were then divided into two groups based on the use or not of ICG for perfusion assessment. Primary outcome was anastomotic leak. Secondary outcomes included operative time, ICG-related adverse reactions, and mortality rate. A meta-analysis was conducted to estimate the overall weighted proportion and its 95% confidence interval (CI) for main outcomes.

RESULTS

A total of 3,171 patients were included for analysis: 381 (12%) with intraoperative ICG fluorescence imaging and 2,790 (88%) without ICG. Mean patients' age and proportion of males were similar between groups. Mean operative time was also similar between both groups (ICG: 354.8 vs. No-ICG: 354.1 minutes, P = 0.52). Mean ICG dose was 12 mg (5-21 mg). No ICG-related adverse reactions were reported. AL rate was 9% (95% CI, 5-17%) and 9% (95% CI, 7-12%) in the ICG and No-ICG groups, respectively. The risk of AL was similar between groups (odds ratio 0.85, 95% CI 0.53-1.28, P = 0.45). Mortality was 3% (95% CI, 1-9%) in patients with ICG and 2% (95% CI, 2-3%) in those without ICG. Median length of hospital stay was also similar between groups (ICG: 13.6 vs. No-ICG: 11.2 days, P = 0.29).

CONCLUSION

The use of ICG fluorescence imaging for perfusion assessment does not seem to reduce AL rates in patients undergoing minimally invasive esophagectomy with intrathoracic anastomosis.

Normalization of Time-Intensity Curves for Quantification of Foot Perfusion Using Near-Infrared Fluorescence Imaging With Indocyanine Green

PURPOSE

Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) is gaining popularity for the quantification of tissue perfusion, including foot perfusion in patients with lower extremity arterial disease (LEAD). However, the absolute fluorescence intensity is influenced by patient-and system-related factors limiting reliable and valid quantification. To enhance the quality of quantitative perfusion assessment using ICG NIR fluorescence imaging, normalization of the measured time-intensity curves seems useful.

MATERIALS AND METHODS

In this cohort study, the effect of normalization on 2 aspects of ICG NIR fluorescence imaging in assessment of foot perfusion was measured: the repeatability and the region selection. Following intravenous administration of ICG, the NIR fluorescence intensity in both feet was recorded for 10 mins using the Quest Spectrum platform^®. The effect of normalization on repeatability was measured in the nontreated foot in patients undergoing unilateral revascularization preprocedural and postprocedural (repeatability group). The effect of normalization on region selection was performed in patients without LEAD (region selection group). Absolute and normalized time-intensity curves were compared.

RESULTS

Successful ICG NIR fluorescence imaging was performed in 54 patients (repeatability group, n = 38; region selection group, n = 16). For the repeatability group, normalization of the time-intensity curves displayed a comparable inflow pattern for repeated measurements. For the region selection group, the maximum fluorescence intensity (Imax) demonstrated significant differences between the 3 measured regions of the foot (P = .002). Following normalization, the time-intensity curves in both feet were comparable for all 3 regions.

CONCLUSION

This study shows the effect of normalization of time-intensity curves on both the repeatability and region selection in ICG NIR fluorescence imaging. The significant difference between absolute parameters in various regions of the foot demonstrates the limitation of absolute intensity in interpreting tissue perfusion. Therefore, normalization and standardization of camera settings are essential steps toward reliable and valid quantification of tissue perfusion using ICG NIR fluorescence imaging.

Objective Perfusion Assessment in Gracilis Muscle Interposition—A Novel Software-Based Approach to Indocyanine Green Derived Near-Infrared Fluorescence in Reconstructive Surgery

Background: Gracilis muscle interposition (GMI) is an established treatment option for complex perineal fistulas and reconstruction. The outcome is limited by complications such as necrosis, impaired wound healing and fistula persistence or recurrence. Quantifiable methods of assessing muscle flap perfusion intraoperatively are lacking. This study evaluates a novel and objective software-based assessment of indocyanine green near-infrared fluorescence (ICG-NIRF) in GMI. Methods: Intraoperative ICG-NIRF visualization data of five patients with inflammatory bowel disease (IBD) undergoing GMI for perineal fistula and reconstruction were analyzed retrospectively. A new software was utilized to generate perfusion curves for the specific regions of interest (ROIs) of each GMI by depicting the fluorescence intensity over time. Additionally, a pixel-to-pixel and perfusion zone analysis were performed. The findings were correlated with the clinical outcome. Results: Four patients underwent GMI without postoperative complications within 3 months. The novel perfusion indicators identified here (shape of the perfusion curve, maximum slope value, distribution and range) indicated adequate perfusion. In one patient, GMI failed. In this case, the perfusion indicators suggested impaired perfusion. Conclusions: We present a novel, software-based approach for ICG-NIRF perfusion assessment, identifying previously unknown objective indicators of muscle flap perfusion. Ready for intraoperative real-time use, this method has considerable potential to optimize GMI surgery in the future.

Biophysics inspired artificial intelligence for colorectal cancer characterization

Over the last ten years artificial intelligence (AI) methods have begun to pervade even the most common everyday tasks such as email filtering and mobile banking. While the necessary quality and safety standards may have understandably slowed the introduction of AI to healthcare when compared with other industries, we are now beginning to see AI methods becoming more available to the clinician in select settings. In this paper we discuss current AI methods as they pertain to gastrointestinal procedures including both gastroenterology and gastrointestinal surgery. The current state of the art for polyp detection in gastroenterology is explored with a particular focus on deep leaning, its strengths, as well as some of the factors that may limit its application to the field of surgery. The use of biophysics (utilizing physics to study and explain biological phenomena) in combination with more traditional machine learning is also discussed and proposed as an alternative approach that may solve some of the challenges associated with deep learning. Past and present uses of biophysics inspired AI methods, such as the use of fluorescence guided surgery to aid in the characterization of colorectal lesions, are used to illustrate the role biophysics-inspired AI can play in the exciting future of the gastrointestinal proceduralist.

Quantitative fluorescence-guided perfusion assessment of the gastric conduit to predict anastomotic complications after esophagectomy

BACKGROUND

Fluorescence angiography (FA) assesses anastomotic perfusion during esophagectomy with gastric conduit reconstruction, but its interpretation is subjective. This study evaluated time to fluorescent enhancement in the gastric conduit, with the aim to determine a threshold to predict postoperative anastomotic complications.

METHODS

In a prospective cohort study, all consecutive patients undergoing esophagectomy with gastric conduit reconstruction from July 2018 to October 2019 were included. FA was performed before anastomotic reconstruction following injection of indocyanine green (ICG). During FA, the following time points were recorded: ICG injection, first fluorescent enhancement in the lung, at the base of the gastric conduit, at the planned anastomotic site, and at ICG watershed or in the tip of the gastric conduit. Anastomotic complications including anastomotic leakage and clinically relevant strictures were documented.

RESULTS

Eighty-four patients were included, the majority (67 out of 84, 80%) of which underwent an Ivor Lewis procedure. After a median follow-up of 297 days, anastomotic leakage was observed in 12 out of 84 (14.3%) and anastomotic stricture in 12 out of 82 (14.6%). Time between ICG injection and enhancement in the tip was predictive for anastomotic leakage (P = 0.174, area under the curve = 0.731), and a cut-off value of 98 seconds was derived (specificity: 98%). All times to enhancement at the planned anastomotic site and ICG watershed were significantly predictive for the occurrence of a stricture, however area under the curves were <0.7.

CONCLUSIONS

The identified fluorescent threshold can be used for intraoperative decision making or to identify potentially high-risk patients for anastomotic leakage after esophagectomy with gastric conduit reconstruction.