Quantification of fluorescence angiography for visceral perfusion assessment: measuring agreement between two software algorithms

BACKGROUND

Indocyanine green fluorescence angiography (ICG-FA) may reduce perfusion-related complications of gastrointestinal anastomosis. Software implementations for quantifying ICG-FA are emerging to overcome a subjective interpretation of the technology. Comparison between quantification algorithms is needed to judge its external validity. This study aimed to measure the agreement for visceral perfusion assessment between two independently developed quantification software implementations.

METHODS

This retrospective cohort analysis included standardized ICG-FA video recordings of patients who underwent esophagectomy with gastric conduit reconstruction between August 2020 until February 2022. Recordings were analyzed by two quantification software implementations: AMS and CPH. The quantitative parameter used to measure visceral perfusion was the normalized maximum slope derived from fluorescence time curves. The agreement between AMS and CPH was evaluated in a Bland-Altman analysis. The relation between the intraoperative measurement of perfusion and the incidence of anastomotic leakage was determined for both software implementations.

RESULTS

Seventy pre-anastomosis ICG-FA recordings were included in the study. The Bland-Altman analysis indicated a mean relative difference of + 58.2% in the measurement of the normalized maximum slope when comparing the AMS software to CPH. The agreement between AMS and CPH deteriorated as the magnitude of the measured values increased, revealing a proportional (linear) bias (R2 = 0.512, p < 0.001). Neither the AMS nor the CPH measurements of the normalized maximum slope held a significant relationship with the occurrence of anastomotic leakage (median of 0.081 versus 0.074, p = 0.32 and 0.041 vs 0.042, p = 0.51, respectively).

CONCLUSION

This is the first study to demonstrate technical differences in software implementations that can lead to discrepancies in ICG-FA quantification in human clinical cases. The possible variation among software-based quantification methods should be considered when interpreting studies that report quantitative ICG-FA parameters and derived thresholds, as there may be a limited external validity.

Management of acute and chronic pelvic sepsis after total mesorectal excision for rectal cancer-a 10-year experience of a national referral centre

AIM

Uncontrolled pelvic sepsis following rectal cancer surgery may lead to dramatic consequences with significant impact on patients' quality of life. The aim of this retrospective observational study is to evaluate management of pelvic sepsis after total mesorectal excision for rectal cancer at a national referral centre.

METHOD

Referred patients with acute or chronic pelvic sepsis after sphincter preserving rectal cancer resection, with the year of referral between 2010 and 2014 (A) or between 2015 and 2020 (B), were included. The main outcome was control of pelvic sepsis at the end of follow-up, with healed anastomosis with restored faecal stream (RFS) as co-primary outcome.

RESULTS

In total 136 patients were included: 49 in group A and 87 in group B. After a median follow-up of 82 months (interquartile range 35-100) in group A and 42 months (interquartile range 22-60) in group B, control of pelvic sepsis was achieved in all patients who received endoscopic vacuum assisted surgical closure (7/7 and 2/2), in 91% (19/21) and 89% (31/35) of patients who received redo anastomosis (P = 1.000) and in 100% (18/18) and 95% (41/43) of patients who received intersphincteric resection (P = 1.000), respectively. Restorative procedures resulted in a healed anastomosis with RFS in 61% (17/28) of patients in group A and 68% (25/37) of patients in group B (P = 0.567).

CONCLUSION

High rates of success can be achieved with surgical salvage of pelvic sepsis in a dedicated tertiary referral centre, without significant differences over time. In well selected and motivated patients a healed anastomosis with RFS can be achieved in the majority.

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.

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.

Understanding fluorescence time curves during ileal pouch-anal anastomosis with or without vascular ligation

BACKGROUND

Intraoperative indocyanine green fluorescence angiography (ICG-FA) may be of added value during pouch surgery, in particular after vascular ligations as lengthening maneuver. The aim was to determine quantitative perfusion parameters within the efferent/afferent loop and explore the impact of vascular ligation. Perfusion parameters were also compared in patients with and without anastomotic leakage (AL).

METHODS

All consenting patients that underwent FA-guided ileal pouch-anal anastomosis (IPAA) between July 2020 and December 2021 were included. After intravenous bolus injection of 0.1 mg/kg ICG, the near-infrared camera (Stryker Aim 1688) registered the fluorescence intensity over time. Quantitative analysis of ICG-FA from standardized regions of interests on the pouch was performed using software. Fluorescence parameters were extracted for inflow (T₀, T_max, F_max, slope, Time-to-peak) and outflow (T_90% and T_80%). Change of management related to FA findings and AL rates were recorded.

RESULTS

Twenty-one patients were included, three patients (14%) required vascular ligation to obtain additional length, by ligating terminal ileal branches in two and the ileocolic artery (ICA) in one patient. In nine patients the ICA was already ligated during subtotal colectomy. ICG-FA triggered a change of management in 19% of patients (n = 4/21), all of them had impaired vascular supply (ligated ileocolic/ terminal ileal branches). Overall, patients with intact vascular supply had similar perfusion patterns for the afferent and efferent loop. Pouches with ICA ligation had longer T_max in both afferent as efferent loop than pouches with intact ICA (afferent 51 and efferent 53 versus 41 and 43 s respectively). Mean slope of the efferent loop diminished in ICA ligated patients 1.5(IQR 0.8-4.4) versus 2.2 (1.3-3.6) in ICA intact patients.

CONCLUSION

Quantitative analysis of ICG-FA perfusion during IPAA is feasible and reflects the ligation of the supplying vessels.

Evaluation of inter-user variability in indocyanine green fluorescence angiography to assess gastric conduit perfusion in esophageal cancer surgery

Indocyanine Green Fluorescence Angiography (ICGFA) has been deployed to tackle malperfusion-related anastomotic complications. This study assesses variations in operator interpretation of pre-anastomotic ICGFA inflow in the gastric conduit. Utilizing an innovative online interactive multimedia platform (Mindstamp), esophageal surgeons completed a baseline opinion-practice questionnaire and proceeded to interpret, and then digitally assign, a distal transection point on 8 ICGFA videos of esophageal resections (6 Ivor Lewis, 2 McKeown). Annotations regarding gastric conduit transection by ICGFA were compared between expert users versus non-expert participants using ImageJ to delineate longitudinal distances with Shapiro Wilk and t-tests to ascertain significance. Expert versus non-expert correlation was assessed via Intraclass Correlation Coefficients (ICC). Thirty participants (13 consultants, 6 ICGFA experts) completed the study in all aspects. Of these, a high majority (29 participants) stated ICGFA should be used routinely with most (21, including 5/6 experts) stating that 11-50 cases were needed for competency in interpretation. Among users, there were wide variations in dosing (0.05-3 mg/kg) and practice impact. Agreement regarding ICGFA video interpretation concerning transection level among experts was 'moderate' (ICC = 0.717) overall but 'good' (ICC = 0.871) among seven videos with Leave One Out (LOO) exclusion of the video with highest disagreement. Agreement among non-experts was moderate (ICC = 0.641) overall and in every subgroup including among consultants (ICC = 0.626). Experts choose levels that preserved more gastric conduit length versus non-experts in all but one video (P = 0.02). Considerable variability exists with ICGFA interpretation and indeed impact. Even adept users may be challenged in specific cases. Standardized training and/or computerized quantitative fluorescence may help better usage.

Iatrogenic injury of the urinary tract during salvage procedures for pelvic sepsis: Experience of a national referral centre

AIM

This study aimed to determine the incidence, consequences and outcomes of iatrogenic urinary tract injury (IUI) during salvage surgery for pelvic sepsis.

METHOD

Patients who underwent salvage surgery for pelvic sepsis after prior low anterior resection or Hartmann's procedure for rectal cancer were prospectively maintained in a database between 2010 and 2020 and reviewed retrospectively. The primary endpoint was the incidence of IUI. Secondary endpoints were timing of diagnosis (intra- vs. postoperative), reinterventions related to the IUI and healing of IUI.

RESULTS

In total 126 consecutive patients were included, and IUI occurred in 13 patients (10%). A ureteric injury occurred in eight patients, bladder injury in four patients and a urethral injury in one patient. All patients with an IUI had radiotherapy as neoadjuvant treatment. The IUI was diagnosed postoperatively in 63% (n = 8/13) with a median duration between surgery and diagnosis of the IUI of 10 days (IQR: 6-15). The median number of reinterventions was five (range 1-31) in the group with a postoperative diagnosis and one (range 0-1) in the group with an intraoperative diagnosis. Four patients required a surgical reintervention, all concerning injuries diagnosed postoperatively. At the end of follow-up, 85% of patients (n = 11/13) had a healed IUI.

CONCLUSION

Iatrogenic urinary tract injury is not uncommon in salvage procedures for pelvic sepsis, even in an experienced tertiary referral centre. Most injuries were diagnosed postoperatively which affects the severity of these complications, emphasising the need to improve intraoperative diagnostic modalities.

The role of fluorescence angiography in colonic interposition after esophagectomy

Colonic interposition is an alternative for gastric conduit reconstruction after esophagectomy. Anastomotic leakage (AL) occurs in 15-25% of patients and may be attributed to reduced blood supply after vascular ligation. Indocyanine green fluorescence angiography (ICG-FA) can visualize tissue perfusion. We aimed to give an overview of the first experiences of ICG-FA and AL rate in colonic interposition. This study included all consecutive patients who underwent a colonic interposition between January 2015 and December 2021 at a tertiary referral center. Surgery was performed for the following indications: inability to use the stomach because of previous surgery or extensive tumour involvement, cancer recurrence in the gastric conduit, or because of complications after initial esophagectomy. Since 2018 ICG-FA was performed before anastomotic reconstruction by administration of ICG injection (0.1 mg/kg/bolus), using the Spy-phi (Stryker, Kalamazoo, MI). Twenty-eight patients (9 female, mean age 62.8), underwent colonic interposition of whom 15 (54%) underwent ICG-FA-guided surgery. Within the ICG-FA group, three (20%) AL occurred, whereas in the non-ICG-FA group, three AL and one graft necrosis (31%) occurred (P=0.67). There was a change of management due to the FA assessment in three patients in the FA group (20%) which led to the choice of a different bowel segment for the anastomosis. Mean operative times in the ICG-FA and non-ICG-FA groups were 372±99 and 399±113 minutes, respectively (P=0.85). ICG-FA is a safe, easy and feasible technique to assess perfusion of colonic interpositions. ICG-FA is of added value leading to a change in management in a considerable percentage of patients. Its role in prevention of AL remains to be elucidated.

The use of fluorescence angiography to assess bowel viability in the acute setting: an international, multi-centre case series

Introduction

Assessing bowel viability can be challenging during acute surgical procedures, especially regarding mesenteric ischaemia. Intraoperative fluorescence angiography (FA) may be a valuable tool for the surgeon to determine whether bowel resection is necessary and to define the most appropriate resection margins. The aim of this study is to report on FA use in the acute setting and to judge its impact on intraoperative decision making.

Materials and methods

This is a multi-centre, retrospective case series of patients undergoing emergency abdominal surgery between February 2016 and 2021 in three general/colorectal units where intraoperative FA was performed to assess bowel viability. Primary endpoint was change of management after the FA assessment.

Results

A total of 93 patients (50 males, 66.6 ± 19.2 years, ASA score ≥ III in 85%) were identified and studied. Initial surgical approach was laparotomy in 66 (71%) patients and laparoscopy in 27 (29% and seven, 26% conversions). The most common aetiologies were mesenteric ischaemia (n = 42, 45%) and adhesional/herniae-related strangulation (n = 41, 44%). In 50 patients a bowel resection was performed. Overall rates of anastomosis after resection, reoperation and 30-day mortality were 48% (n = 24/50, one leak), 12% and 18%, respectively. FA changed management in 27 (29%) patients. In four patients (4% overall), resection was avoided and in 21 (23%) extra bowel length was preserved (median 50 cm of bowel saved, IQR 28–98) although three patients developed further ischaemia. FA prompted extended resection (median of 20 cm, IQR 10–50 extra bowel) in six (6%) patients.

Conclusion

Intraoperative use of FA impacts surgical decisions regarding bowel resection for intestinal ischaemia, potentially enabling bowel preservation in approximately one out of four patients. Prospective studies are needed to optimize the best use of this technology for this indication and to determine standards for the interpretation of FA images and the potential subsequent need for second-look surgeries.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00464-022-09136-7.

In vivo destruction of tumor tissue by cryoablation can induce inhibition of secondary tumor growth: an experimental study

BACKGROUND

Cryoablation has been used successfully for the local treatment of several cancers. Besides local destruction, a systemic antitumor response has been postulated after cryoablation of tumor tissue. In this study we evaluate the possible systemic antitumor response induced by cryodestruction of tumor tissue in two mouse tumor models.

METHODS

Mice received two subcutaneously placed tumor implants (thigh and flank) of the nonimmunogenic mouse colon tumor cell line, colon 26-B. After 7 days, the thigh implant was treated by cryoablation or excision and the effect on secondary tumor growth was determined by volume measurement of the nontreated flank tumor. Cytokine (IL-1alpha and TNF-alpha) levels in plasma were measured after treatment. Similar experiments were performed in nude mice using a human melanoma cell line (MV3). Moreover, in this model the effect of cryoablation on development of spontaneous lung metastases was evaluated.

RESULTS

In the colon 26-B tumor model treatment of primary tumor implants by cryoablation resulted in a significant inhibition of secondary tumor growth compared to animals treated by surgical excision (P < 0.01). Six hours after treatment, plasma levels of IL-1alpha and TNF-alpha were higher after cryoablation than after excision (P < 0.01). Also in the nude mice model cryoablation resulted in inhibition of secondary tumor growth, though not significant. Mice treated by cryoablation showed significantly less lung metastases compared to those treated by excision (P = 0.03).

CONCLUSIONS

Cryoablation of tumor tissue can result in inhibition of secondary and metastatic tumor growth. A cytokine response induced by cryoablation of tumor tissue may attribute to this feature.

Intraoperative lymphatic mapping and the sentinel node concept in colorectal carcinoma

BACKGROUND

Orderly progression of nodal metastases has been described for melanoma and breast cancer. The first draining lymph node, the sentinel node, is also the first to contain metastases and accurately predicts nodal status. The aim of this study was to assess the feasibility of lymphatic mapping and sentinel node biopsy in colorectal cancer.

METHODS

In 50 patients with colorectal cancer patent blue dye was injected around the tumour. After resection of the tumour the specimen was examined to identify blue-stained lymph nodes. Routine histopathological examination was performed on all nodes and the blue, haematoxylin and eosin-stained tumour-negative nodes were tested immunohistochemically.

RESULTS

Lymphatic mapping was possible in 35 of 50 patients (70 per cent). Pathological examination with haematoxylin and eosin staining showed lymph node metastases in 20 of 35 patients. In eight of these 20 patients the blue nodes showed tumour, while in 12 the blue nodes were not involved. This represents a false-negative rate of 60 per cent.

CONCLUSION

Lymphatic mapping using patent blue dye is feasible in colorectal cancer. The blue-stained nodes do not predict nodal status of the remaining lymph nodes in the resected specimen. The concept of lymphatic mapping and sentinel node identification is not valid for colorectal cancer.