Fluorescence-enabled assessment of adrenal gland localization and perfusion in posterior retroperitoneoscopic adrenal surgery in a preclinical model

Dynamic full-field optical coherence tomography for extemporaneous high-resolution imaging of adrenal glands

BACKGROUND

There is an interindividual variance in postoperative adrenocortical capacity, and the minimal functional remnant size is unknown. New imaging technologies may allow for improved intraoperative assessment of adrenal tissue morphology, cell activity, and surgery-related changes. The aim of this experimental study was to provide a pilot assessment of adrenal gland architecture with dynamic full-field optical coherence tomography (D-FF-OCT) in comparison to standard hematoxylin-eosin (HE) examination.

METHODS

D-FF-OCT was performed on freshly resected porcine adrenal glands to simultaneously assess both morphology and metabolic activity in real time, and for comparison with standard histopathology. Left and right adrenal glands were assessed from 8 pigs (1 M, 7 F, mean weight 43.9 ± 8.3 kg).

RESULTS

The evaluation with D-FF-OCT proved fast in terms of acquisition time, averaging 32 min/specimen. The technique required a relatively short learning curve and provided morphological details similar to standard microscopy. In the comparative analysis of both methods, D-FF-OCT scans allowed easy identification of normal adrenal morphology and facilitated differentiation of the structural components of the cortical and medullary areas based on architectural and vascular patterns. Furthermore, it was possible to distinguish more accurately between cell subpopulations based on their metabolic activity.

CONCLUSION

While HE examination remains the gold standard for morphological evaluation, time weighs heavy on this ancillary technique. In our study, we prove that D-FF-OCT is effective in achieving a comparable level of morphological details, with added metabolic activity of the cells, a combination which can prove useful in the real-time assessment of various diseases requiring adrenal surgery.

Single-Plane Retroperitoneoscopic Adrenalectomy Guided by Indocyanine Green Dye: An Optimized Step

Background: The objective of this study was to explore the perioperative outcomes of single-plane posterior retroperitoneoscopic adrenalectomy (SPRA) guided by indocyanine green dye (ICG) fluorescence imaging. Methods: A retrospective analysis of patients who underwent SPRA from April to September 2023 in our center was conducted. Patients were divided into the ICG group and the non-ICG group, based on whether they received intraoperative ICG fluorescence guided or not. Baseline and perioperative data were recorded and analyzed by R software (R 4.3.1). Results: A total of 23 patients were enrolled in the study, with 12 in the ICG group and 11 in the non-ICG group. The demographics including age, gender, body mass index, or American Society of Anesthesiologists classification showed no significant differences between groups. There were obvious advantages in shortening adrenal gland localization time and total operative time, as well as reducing estimated blood loss in the ICG group compared with the non-ICG group (5.58 ± 0.36 minutes vs 7.55 ± 0.62 minutes, p < 0.001; 27.50 ± 5.46 minutes vs 45.00 ± 10.99 minutes, p < 0.001; 22.91 ± 7.57 mL vs 54.54 ± 18.90 mL, p < 0.001; respectively). Furthermore, patients in the ICG group exhibited significantly lower visual analog pain scale scores at 24 hours postoperatively and at discharge (p = 0.001 and p = 0.006, respectively). The oral intake intervals, hospital stays, and perioperative complications were comparable between groups. Conclusions: ICG-guided SPRA could be a safe and effective procedure for patients with adrenal tumors. This technique improves the accuracy and efficacy of adrenal gland localization and has shown benefits in perioperative outcomes. The use of ICG fluorescence guidance represents a promising clinical application.

Tailored Approach in Adrenal Surgery: Retroperitoneoscopic Partial Adrenalectomy

The interest on partial adrenalectomy has steadily increased over the past twenty years. Adrenal pathologies are mostly benign, making an organ-preserving procedure attractive for many patients. The introduction of minimally invasive techniques played probably an important role in this process because they transformed a complex surgical procedure, related to the difficult access to the retroperitoneal space, into a simple operation improving the accessibility to this organ. In this review we summarize the role of partial retroperitoneoscopic adrenalectomy over the years and the current indications and technique.

Fluorescence Image-Guided Surgery for Thyroid Cancer: Utility for Preventing Hypoparathyroidism

Background: Hypoparathyroidism is one of the most frequent complications of thyroid surgery, especially when associated with lymph node dissection in cases of thyroid cancer. Fluorescence-guided surgery is an emerging tool that appears to help reduce the rate of this complication. The present review aims to highlight the utility of fluorescence imaging in preserving parathyroid glands during thyroid cancer surgery. Methods: We performed a systematic review of the literature according to PRISMA guidelines to identify published studies on fluorescence-guided thyroid surgery with a particular focus on thyroid cancer. Articles were selected and analyzed per indication and type of surgery, autofluorescence or exogenous dye usage, and outcomes. The Methodological Index for Non-Randomized Studies (MINORS) was used to assess the methodological quality of the included articles. Results: Twenty-five studies met the inclusion criteria, with three studies exclusively assessing patients with thyroid cancer. The remaining studies assessed mixed cohorts with thyroid cancer and other thyroid or parathyroid diseases. The majority of the papers support the potential benefit of fluorescence imaging in preserving parathyroid glands in thyroid surgery. Conclusions: Fluorescence-guided surgery is useful in the prevention of post-thyroidectomy hypoparathyroidism via enhanced early identification, visualization, and preservation of the parathyroid glands. These aspects are notably beneficial in cases of associated lymphadenectomy for thyroid cancer.

Robotic approach for partial adrenalectomy

Although safe and feasible, partial adrenalectomy is not a widespread procedure. Endorsement of robotic technologies and fluorescence techniques in adrenal surgery might help develop partial adrenalectomy and could avoid unnecessary total adrenalectomies. When performed in selected cases, partial adrenalectomy is associated with good postoperative outcomes comparable with those reported after total adrenalectomy. It has been hypothesized that one of the advantages of the robotic approach in adrenal-sparing surgery is to reduce manipulation of the gland allowing preservation of the vascularization of the residual adrenal, overcoming some limits when performing a laparoscopic conventional approach. A major drawback of the robotic surgery is its cost, but the overcost due to the use of the robotic system could be balanced by the execution of a high number of partial adrenalectomies leading to fewer life-long replacement steroid treatment. Partial adrenalectomy could become the recommended management for small benign and hormonal active adrenal tumors. Indocyanine green fluorescence (IGF) also seems to be a useful technique to help surgeons identify the adrenal gland and to locate small tumors from the normal adrenal tissue in difficult patients. It is likely that the use of a robotic approach associated with IGF may extend indications of partial adrenalectomy in the years to come.

Intraoperative imaging for remnant viability assessment in bilateral posterior retroperitoneoscopic partial adrenalectomy in an experimental model

BACKGROUND

A surgical approach preserving functional adrenal tissue allows biochemical cure while avoiding the need for lifelong steroid replacement. The aim of this experimental study was to evaluate the impact of intraoperative imaging during bilateral partial adrenalectomy on remnant perfusion and function.

METHODS

Five pigs underwent bilateral posterior retroperitoneoscopic central adrenal gland division (9 divided glands, 1 undivided). Intraoperative perfusion assessment included computer-assisted quantitative fluorescence imaging, contrast-enhanced CT, confocal laser endomicroscopy (CLE) and local lactate sampling. Specimen analysis after completion adrenalectomy (10 adrenal glands) comprised mitochondrial activity and electron microscopy.

RESULTS

Fluorescence signal intensity evolution over time was significantly lower in the cranial segment of each adrenal gland (mean(s.d.) 0·052(0·057) versus 0·133(0·057) change in intensity per s for cranial versus caudal parts respectively; P = 0·020). Concordantly, intraoperative CT in the portal phase demonstrated significantly lower contrast uptake in cranial segments (P = 0·031). In CLE, fluorescein contrast was observed in all caudal segments, but in only four of nine cranial segments (P = 0·035). Imaging findings favouring caudal perfusion were congruent, with significantly lower local capillary lactate levels caudally (mean(s.d.) 5·66(5·79) versus 11·58(6·53) mmol/l for caudal versus cranial parts respectively; P = 0·008). Electron microscopy showed more necrotic cells cranially (P = 0·031). There was no disparity in mitochondrial activity (respiratory rates, reactive oxygen species and hydrogen peroxide production) between the different segments.

CONCLUSION

In a model of bilateral partial adrenalectomy, three intraoperative imaging modalities consistently discriminated between regular and reduced adrenal remnant perfusion. By avoiding circumferential dissection, mitochondrial function was preserved in each segment of the adrenal glands. Surgical relevance Preservation of adrenal tissue to maintain postoperative function is essential in bilateral and hereditary adrenal pathologies. There is interindividual variation in residual adrenocortical stress capacity, and the minimal functional remnant size is unknown. New intraoperative imaging technologies allow improved remnant size and perfusion assessment. Fluorescence imaging and contrast-enhanced intraoperative CT showed congruent results in evaluation of perfusion. Intraoperative imaging can help to visualize the remnant vascular supply in partial adrenalectomy. Intraoperative assessment of perfusion may foster maximal functional tissue preservation in bilateral adrenal pathologies and procedures.

Simultaneous computer-assisted assessment of mucosal and serosal perfusion in a model of segmental colonic ischemia

BACKGROUND

Fluorescence-based enhanced reality (FLER) enables the quantification of fluorescence signal dynamics, which can be superimposed onto real-time laparoscopic images by using a virtual perfusion cartogram. The current practice of perfusion assessment relies on visualizing the bowel serosa. The aim of this experimental study was to quantify potential differences in mucosal and serosal perfusion levels in an ischemic colon segment.

METHODS

An ischemic colon segment was created in 12 pigs. Simultaneous quantitative mucosal and serosal fluorescence imaging was obtained via intravenous indocyanine green injection (0.2 mg/kg), using two near-infrared camera systems, and computer-assisted FLER analysis. Lactate levels were measured in capillary blood of the colonic wall at seven regions of interest (ROIs) as determined with FLER perfusion cartography: the ischemic zone (I), the proximal and distal vascularized areas (PV, DV), and the 50% perfusion threshold proximally and distally at the mucosal and serosal side (P50M, P50S, D50M, D50S).

RESULTS

The mean ischemic zone as measured (mm) for the mucosal side was significantly larger than the serosal one (56.3 ± 21.3 vs. 40.8 ± 14.9, p = 0.001) with significantly lower lactate values at the mucosal ROIs. There was a significant weak inverse correlation between lactate and slope values for the defined ROIs (r = - 0.2452, p = 0.0246).

CONCLUSIONS

Mucosal ischemic zones were larger than serosal zones. These results suggest that an assessment of bowel perfusion from the serosal side only can underestimate the extent of ischemia. Further studies are required to predict the optimal resection margin and anastomotic site.