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.

Rationale and Preclinical Data Supporting Bariatric Arterial Embolization

The prevalence of obesity is increasing globally, leading to significantly increased morbidity, mortality, and health care costs. However, there is a lack of effective treatment options that can treat patients with obesity less invasively than with bariatric surgery. Bariatric arterial embolization (BAE) is an image-guided, minimally invasive, percutaneous procedure that is currently being investigated in preclinical animal models and early clinical trials. If successful, BAE may represent a viable interventional approach for obesity treatment. The purpose of this article is to introduce the physiological and anatomical rationale for BAE, review techniques involved in performing BAE for weight modulation, and provide up-to-date preclinical evidence that supports the translation of BAE into patients.

The GAMMA concept (gastrointestinal activity manipulation to modulate appetite) preliminary proofs of the concept of local vibrational gastric mechanical stimulation

BACKGROUND

Mechanical stimulation of the stretch receptors of the gastric wall can simulate the presence of indigested food leading to reduced food intake. We report the preliminary experimental results of an innovative concept of localized mechanical gastric stimulation.

METHODS

In a first survival study, a biocompatible bulking agent was injected either in the greater curvature (n = 8) or in the cardia wall (n = 8) of Wistar rats. Six animals served as sham. Changes of bulking volume, leptin levels and weight gain were monitored for 3 months. In a second acute study, a micro-motor (n = 10; MM) or a size-paired inactive device (n = 10; ID) where applied on the cardia, while 10 additional rats served as sham. Serum ghrelin and leptin were measured at baseline and every hour (T0-T1-T2-T3), during 3 h. In a third study, 24 implants of various shapes and sizes were introduced into the gastric subserosa of 6 Yucatan pigs. Monthly CT scans and gastroscopies were done for 6 months.

RESULTS

Weight gain in the CW group was significant lower after 2 weeks and 3 months when compared to the shame and GC (p = 0.01/p = 0.01 and p = 0.048/p = 0.038 respectively). Significant lower increase of leptin production occurred at 2 weeks (p = 0.01) and 3 months (p = 0.008) in CW vs. SG. In the MM group significant reduction of the serum ghrelin was seen after 3 h. Leptin was significantly increased in both MM and ID groups after 3 h, while it was significantly reduced in sham rats. The global device retention was 43.5%. Devices with lower profile and with a biocompatible coating remained more likely in place without complications.

CONCLUSIONS

Gastric mechanical stimulation induced a reduced weight gain and hormonal changes. Low profile and coated devices inserted within the gastric wall are more likely to be integrated.

Gastrointestinal Hormones Manipulation to Counteract Metabolic Syndrome Using Duodenal Targeted Embolization

PURPOSE

Targeted embolization of gastrointestinal (GI) arteries can modify hormonal production. We aimed to evaluate the impact of the embolization of the gastroduodenal artery (GDA) on the activity of foregut mucosa.

METHODS

The GDA's duodenal branch was embolized in 12 Yucatan pigs using 100-300 µm (group A; n = 4) or 300-500 µm (group B; n = 4) microspheres, followed by coiling of the branch. In 4 animals (sham), only saline was injected. The levels of GI hormones (ghrelin, glucose-dependent insulinotropic peptide [GIP], glucagon-like peptide-1 [GLP-1], insulin, peptide YY [PYY], leptin) and the gene expression of sodium-glucose-linked transporter-1 (SGLT-1) and glucose transporter-2 (GLUT-2) were assessed before (T0), 1 hour (T1), 1 month (T2), 3 months (T3), and 6 months (T4) after embolization.

RESULTS

In group A, a segmental duodenal stenosis occurred in all cases, which required balloon dilatation. There was a significant drop in the baseline glycemia in group A at T1 and T4 versus sham. Ghrelin was reduced in group A versus baseline and versus group B at T2 and T3 and versus sham at T1 and T3. Insulin was significantly lower in group A versus B at T1 and at T4 but not versus sham. SGLT-1 expression increased in B and sham at T4, while it remained stable in group A. GLUT-2 expression increased in sham at T4 but not in A or B.

CONCLUSIONS

GDA embolization induced a decrease in ghrelin production and influenced expression of glucose carriers in the foregut mucosa.

Discrimination between arterial and venous bowel ischemia by computer-assisted analysis of the fluorescent signal

BACKGROUND

Arterial blood supply deficiency and venous congestion both play a role in anastomotic complications. Our aim was to evaluate a software-based analysis of the fluorescence signal to recognize the patterns of bowel ischemia.

METHODS

In 18 pigs, two clips were applied on the inferior mesenteric artery (group A: n = 6) or vein (group V: n = 6) or on both (group A-V: n = 6). Three regions of interest (ROIs) were identified on the sigmoid: P = proximal to the first clip; C = central, between the two clips; and D = distal to the second clip. Indocyanine Green was injected intravenously. The fluorescence signal was captured by means of a near-infrared laparoscope. The time-to-peak (seconds) and the maximum fluorescence intensity were recorded using software. A normalized fluorescence intensity unit (NFIU: 0-to-1) was attributed, using a reference card. The NFIU's over-time variations were computed every 10 min for 50 min. Capillary lactates were measured on the sigmoid at the 3 ROIs. Various machine learning algorithms were applied for ischemia patterns recognition.

RESULTS

The time-to-peak at the ischemic ROI C was significantly longer in group A versus V (20.1 ± 13 vs. 8.43 ± 3.7; p = 0.04) and in group A-V versus V (20.71 ± 11.6 vs. 8.43 ± 3.7; p = 0.03). The maximal NIFU at ROI C, was higher in the V group (1.01 ± 0.21) when compared to A (0.61 ± 0.11; p = 0.002) and A-V (0.41 ± 0.2; p = 0.0005). Capillary lactates at ROI C were lower in V (1.3 ± 0.6) than in A (1.9 ± 0.5; p = 0.0071), and A-V (2.6 ± 1.5; p = 0.034). The K nearest neighbor and the Linear SVM algorithms provided both an accuracy of 75% in discriminating between A versus V and 85% in discriminating A versus A-V. The accuracy dropped to 70% when the ML had to identify the ROI and the type of ischemia simultaneously.

CONCLUSIONS

The computer-assisted dynamic analysis of the fluorescence signal enables the discrimination between different bowel ischemia models.

Bariatric manipulation of gastric arteries: A systematic review on the potential concept for treatment of obesity

BACKGROUND

Gastric artery embolization (GAE) has recently received attention as a minimally invasive intervention in bariatric setting.

AIMS

The current systematic review aimed to gather and categorizes the existing data in the literature regarding bariatric gastric artery manipulation. This will highlight the importance of this potential concept as a therapeutic modality.

METHODS

A PubMed/Medline search was conducted to identify animal and human studies investigating the effect of gastric artery manipulation on weight, ghrelin, obesity, and tissue adiposity.

RESULTS

A total of 9 studies including 6 animal experiments with 71 subjects and 3 human studies with a total of 25 patients were retrieved. Animal subjects underwent chemical embolization while particle embolization was only used in human subjects. Five animal studies and 1 human study reported decreased ghrelin concentration. Three animal experiments and 2 human studies showed a significant weight change following GAE. There was no report regarding a serious adverse event requiring surgical or interventional management.

CONCLUSION

Currently, data regarding the potential role of gastric artery manipulation in decreasing the ghrelin and potential weight loss is scarce.

A Novel Endoscopic Bariatric Procedure: Results of an Experimental Study

BACKGROUND

Surgical treatment of obesity is characterized by both early and late complications, and thus, there is a need to develop safe and non-invasive techniques. Ghrelin is an orexigenic hormone produced by the fundus of the stomach, which may represent a novel target for obesity management. Unfortunately, numerous attempts to alter ghrelin levels have failed to present significant clinical results. We describe a novel procedure that involves modifying arterial blood flow to the gastric fundus for limiting plasma ghrelin levels.

METHODS

A gastroscope was advanced into the gastric fundus of 13 healthy Yorkshire swine, and the fundus was clipped under direct visualization to restrict left gastric artery blood flow. Body weights and ghrelin levels were recorded before and once a week for 4 weeks after the procedure.

RESULTS

Compared to controls, gastroscopic clipping of the fundus decreased plasma ghrelin levels and prevented further weight gain in the 4 weeks of follow-up. Immunohistochemistry and histomorphometry revealed reduced numbers of ghrelin-positive cells in the fundus of experimental animals. We also observed thrombosis in submucosal arteries and submucosal fibrosis. Histological studies demonstrated minimal gastric mucosal injury.

CONCLUSION

Gastroscopic clipping of the fundus in an experimental porcine model resulted in sustained weight loss and a reduction in plasma ghrelin levels at 1 month post-procedure, with no adverse events. Further experimental studies in human patients are needed to examine the clinical utility of this procedure and to optimize a technique, which can facilitate adequate weight loss while minimizing the risk of mucosal injury.

Metabolism-Guided Bowel Resection

Background. Strip-based handheld devices can measure lactatemia on capillary blood obtained by needle puncturing. We aimed to assess the kinetic of bowel capillary lactates, metabolomics profiling, and mitochondria respiratory rate in a prolonged model of bowel hypoperfusion. Materials and Methods. In 6 pigs, a 3- to 4-cm ischemic segment was created in 6 small bowel loops (total = 36 loops) by clamping the vascular supply, for a duration of 1 to 6 hours. Hourly, 5 blood samples were obtained by puncturing the serosa, and lactates were measured using a handheld analyzer. Samples were made at the following regions of interest (ROIs): center of the ischemic area (1), proximal and distal clinical margins of resection (2a-2b), and vascularized zones (3a-3b). Every hour, surgical biopsies of ROIs were sampled. Activity of bowel mitochondria complexes was measured after 1, 3, and 5 hours of ischemia. Quantification of metabolites was performed on all samples (total N = 180). Results. Capillary lactates were significantly higher at ROI 1 versus ROI 3ab at all time points. After 1 hour lactates at the margins were significantly higher than those at vascularized areas ( P = .0095), showing a mismatch between visual assessment and actual perfusion status. From 2 to 6 hours, there was no difference in lactates between ROIs 2a-2b and 3a-3b. Maximal tissue respiration decreased significantly after 1 hour (ROI 1 vs ROI 3ab). Seven metabolites (lactate, glucose, aspartate, choline, creatine, taurine, and tyrosine) expressed significantly different evolutions between ROIs. Conclusions. Capillary lactates could help precisely estimate local bowel perfusion status.