Intraoperative visualization of pancreatic juice leaking from the pancreatic stump in a swine model

Evaluation of pancreatic chymotrypsin activity for on-site prediction of clinically relevant postoperative pancreatic fistula

OBJECTIVES

Although the risk of complications due to postoperative pancreatic fistula (POPF) have been evaluated based on the amylase level in drained ascitic fluid, this method has much room for improvement regarding diagnostic accuracy and facility of the measurement. This study aimed to investigate the clinical value of measuring pancreatic chymotrypsin activity for rapid and accurate prediction of POPF after pancreaticoduodenectomy.

METHODS

In 52 consecutive patients undergoing pancreaticoduodenectomy, the chymotrypsin activity in pancreatic juice was measured by calculating the increase in fluorescence intensity during the first 5 min after activation with an enzyme-activatable fluorophore. The predictive value for clinically relevant POPF (CR-POPF) was compared between this technique and the conventional method based on the amylase level.

RESULTS

According to receiver operating characteristic analyses, pancreatic chymotrypsin activity on postoperative day (POD) 3 measured with a multiplate reader had the highest predictive value for CR-POPF (area under the curve [AUC], 0.752; P < 0.001), yielding 77.8 % sensitivity and 68.8 % specificity. The AUC and sensitivity/specificity of the amylase level in ascitic fluid on POD 3 were 0.695 (P = 0.053) and 77.8 %/41.2 %, respectively. Multivariable analysis identified high pancreatic chymotrypsin activity on POD 3 as an independent risk factor for CR-POPF. Measurement of pancreatic chymotrypsin activity with a prototype portable fluorescence photometer could significantly predict CR-POPF (AUC, 0.731; P = 0.010).

CONCLUSION

Measurement of pancreatic chymotrypsin activity enabled accurate and rapid prediction of CR-POPF after pancreaticoduodenectomy. This can help surgeons to implement appropriate drain management at the patient's bedside without delay.

Intraoperative visualisation of pancreatic leakage (ViP): study protocol for an IDEAL Stage I Post Market Clinical Study

INTRODUCTION

Pancreatic resections are an important field of surgery worldwide to treat a variety of benign and malignant diseases. Postoperative pancreatic fistula (POPF) remains a frequent and critical complication after partial pancreatectomy and affects up to 50% of patients. POPF increases mortality, prolongs the postoperative hospital stay and is associated with a significant economic burden. Despite various scientific approaches and clinical strategies, it has not yet been possible to develop an effective preventive tool. The SmartPAN indicator is the first surgery-ready medical device for direct visualisation of pancreatic leakage already during the operation. Applied to the surface of pancreatic tissue, it detects sites of biochemical leak via colour reaction, thereby guiding effective closure and potentially mitigating POPF development.

METHODS AND ANALYSIS

The ViP trial is a prospective single-arm, single-centre first in human study to collect data on usability and confirm safety of SmartPAN. A total of 35 patients with planned partial pancreatectomy will be included in the trial with a follow-up of 30 days after the index surgery. Usability endpoints such as adherence to protocol and evaluation by the operating surgeon as well as safety parameters including major intraoperative and postoperative complications, especially POPF development, will be analysed.

ETHICS AND DISSEMINATION

Following the IDEAL-D (Idea, Development, Exploration, Assessment, and Long term study of Device development and surgical innovation) framework of medical device development preclinical in vitro, porcine in vivo, and human ex vivo studies have proven feasibility, efficacy and safety of SmartPAN. After market approval, the ViP trial is the IDEAL Stage I trial to investigate SmartPAN in a clinical setting. The study has been approved by the local ethics committee as the device is used exclusively within its intended purpose. Results will be published in a peer-reviewed journal. The study will provide a basis for a future randomised controlled interventional trial to confirm clinical efficacy of SmartPAN.

TRIAL REGISTRATION NUMBER

German Clinical Trial Register DRKS00027559, registered on 4 March 2022.

Closure and anastomosis of the pancreas using a four-needle three-loop suture device

Pancreatic juice can leak not only from the main pancreatic duct but also from unclosed ductal branches appearing on the pancreatic stump. We have developed a suture device consisting of three loops of suture attached to four small-curvature needles with the aim to maximize the area of pancreatic parenchyma to be ligated and reduce the number of punctures made on the pancreas during pancreatic closure or anastomosis. In pancreatojejunostomy, the dorsal wall of the jejunum and then the pancreatic parenchyma are sutured using the four needles. Following duct-to-mucosa anastomosis, the ventral jejunal wall is sutured, and the three threads are finally tied sequentially to complete the reconstruction following the Blumgart method. In distal pancreatectomy, the pancreatic stump is sutured from the dorsal aspect sequentially using the four needles, before or after the pancreatic transection. The three threads are then respectively tied on the ventral surface of the pancreas. This device was used in six pancreatoduodenectomies (including two minimally invasive procedures) and five distal pancreatectomies. A postoperative pancreatic fistula requiring additional drainage or repositioning of abdominal drains developed in two patients. No adverse events associated with this device were encountered. The four-needle three-loop suture device can be an alternative to conventional staplers or sutures for closure and anastomosis of the pancreatic stump.

SmartPAN: in vitro and in vivo proof-of-safety assessments for an intra-operative predictive indicator of postoperative pancreatic fistula

Pancreatic surgery is complicated by untreated fluid leakage, but no tenable techniques exist to detect and close leakage sites during surgery. A novel hydrogel called SmartPAN has been developed to meet this need and is here assessed for safety before trials on human patients. Firstly, resazurin assays were used to test the cytotoxic effects of SmartPAN's active bromothymol blue (BTB) indicator and its solution of phosphate-buffered saline (PBS) on normal (HPDE: Human Pancreatic Duct Epithelial) or carcinomic (FAMPAC) human pancreatic cells. Cells incubated with BTB showed no significant reduction in cell viability below threshold safety levels. However, PBS had a mild cytotoxic effect on FAMPAC cells. Secondly, SmartPAN's pathological effects were evaluated in vivo by applying 4 mL SmartPAN to a porcine (Sus scrofa domesticus) model of pancreatic resection. There were no significant differences in macroscopic and microscopic pathologies between pigs treated with SmartPAN or saline. Thirdly, measurements using HPLC-MS/MS demonstrate that BTB does not cross into the bloodstream and was eliminated from the body within two days of surgery. Overall, SmartPAN appears safe in the short-term and ready for first-in-human trials because its components are either biocompatible or quickly neutralized by dilution and drainage.

Applying an intraoperative predictive indicator for postoperative pancreatic fistula: randomized preclinical trial

Leaking pancreatic fluid can contribute to postoperative pancreatic fistula (POPF), which can complicate pancreatic surgery. Surgeons lack reliable tools to identify pancreatic leaks, so a novel hydrogel indicator called SmartPAN was developed for intraoperative application. In this preclinical efficacy assessment study, SmartPAN was capable of detecting sites associated with biochemical leak and POPF-related symptoms, thereby guiding effective closure. Thus, SmartPAN may help to reduce POPF development in upcoming clinical trials.

A novel reaction force-fluorescence measurement system for evaluating pancreatic juice leakage from an excised swine pancreas during distal pancreatectomy

BACKGROUND

Resection using a stapler is a popular approach to distal pancreatectomy. However, the resulting leakage of pancreatic juice represents a serious problem. We have developed a force-fluorescence measurement as a first step towards the quantitative evaluation of pancreatic leakage due to tissue tearing under compression.

METHODS

The system comprises a testing machine with an indenter, similar in size to a stapler, which controls compression speed and measures reaction force, and a fluorescence measurement system to measure pancreatic juice leakage. Pancreatic juice leakage is measured as the maximum value of the increasing rate of fluorescence intensity (max value). Ten excised swine pancreases were compressed at a speed of 500, 100, and 10 mm/min until their thicknesses became 2 mm.

RESULTS

A strong positive correlation (0.804) was observed between the increase in max value before and after compression and the amount of reaction force drop due to tissue destruction. No pancreatic juice leakage was observed when compressed slowly (10 mm/min).

CONCLUSIONS

We have successfully developed a novel force-fluorescence measurement system that can detect and quantify pancreatic juice leakage caused by tissue tearing. This system can determine the optimal compression conditions for preventing pancreatic juice leakage.

On-Site Monitoring of Postoperative Bile Leakage Using Bilirubin-Inducible Fluorescent Protein

Background

Bile leakage is the most common postoperative complication associated with hepatobiliary and pancreatic surgery. Until now, however, a rapid, accurate diagnostic method for monitoring intraoperative and postoperative bile leakage had not been established.

Method

Bilirubin levels in drained abdominal fluids collected from 23 patients who had undergone hepatectomy (n = 22) or liver transplantation (n = 1) were measured using a microplate reader with excitation/emission wavelengths of 497/527 nm after applying 5 µM of UnaG to the samples. UnaG was also sprayed directly on hepatic raw surfaces in swine hepatectomy models to identify bile leaks by fluorescence imaging.

Results

The bilirubin levels measured by UnaG fluorescence imaging showed favorable correlations with the results of the conventional light-absorptiometric methods (indirect bilirubin: rs = 0.939, p < 0.001; direct bilirubin: rs = 0.929, p < 0.001). Approximate time required for bilirubin measurements with UnaG was 15 min, whereas it took about 40 min with the conventional method at a hospital laboratory. Following administration of UnaG on hepatic surfaces, the fluorescence imaging identified bile leaks not only on the resected specimens but also in the abdominal cavity of the swine hepatectomy models.

Conclusion

Fluorescence imaging techniques using UnaG may enable real-time identification of bile leaks during hepatectomy and on-site rapid diagnosis of bile leaks after surgery.

Electronic supplementary material

The online version of this article (10.1007/s00268-020-05774-x) contains supplementary material, which is available to authorized users.

SmartPAN: A novel polysaccharide-microsphere-based surgical indicator of pancreatic leakage

Postoperative pancreatic fistula is a major surgical complication that can follow pancreatic resection. Postoperative pancreatic fistula can develop as a consequence of leaking pancreatic fluid, which calls for an intraoperative indicator of leakage. But suitable indicators of pancreatic leakage have yet to be found. This study details the evidence-based development and early efficacy assessments of a novel pancreatic leakage indicator (SmartPAN), following the IDEAL framework of product development. We developed 41 SmartPAN prototypes by combining indicators of pancreatic fluid with a polysaccharide-microsphere matrix. The prototypes were assessed in vitro using porcine ( Sus scrofa domesticus) pancreatic tissue and ex vivo with human pancreatic fluid. From these initial tests, we chose a hydrogel-based compound that uses the pH indicator bromothymol blue to detect alkali pancreatic fluid. This prototype was then assessed in vivo for usability, effectiveness and reliability using a porcine model. Treatment groups were defined by SmartPAN-reaction at initial pancreatic resection: indicator-positive or negative. Indicator-positive individuals randomly received either targeted closure of leakage sites or no further closure. We assessed SmartPAN’s reliability and effectiveness by monitoring abdominal drainage for amylase and with relaparotomy after 48 h. SmartPAN responses were consistent between both surgical procedures and conformed to amylase measurements. In conclusion, we have developed the first surgery-ready indicator for predicting the occurrence of pancreatic leakage during pancreatic resection. SmartPAN can enable targeted prophylactic closure in a simple and reliable way, and thus may reduce the impact of postoperative pancreatic fistula by guiding peri- and post-operative management.

Has the pancreatic fistula already occurred in the operation? An intraoperative predictive factor of clinical relevant-postoperative pancreatic fistula after the distal pancreatectomy

Purpose

The aim of this study was to assess the predictive effect of intraoperative amylase value from pancreatic remnant on the development of clinical relevant-postoperative pancreatic fistula after distal pancreatectomy.

Methods

Patients undergoing distal pancreatectomy between June 2017 and October 2018 were studied retrospectively. The intraoperative amylase value was measured followed by drain fluid for amylase on postoperative day 3. The analysis of clinical relevant-postoperative pancreatic fistula predictors was carried out using the logistic regression. The receiver operating characteristic analysis was performed to evaluate the discriminative capacity of intraoperative amylase value as a predictive risk factor.

Results

The study population consisted of 40 patients. The clinical relevant-postoperative pancreatic fistula occurred in 13 patients, no grade C pancreatic fistula (PF). The intraoperative amylase value correlated significantly with clinical relevant-postoperative pancreatic fistula. An intraoperative amylase value > 3089 U/L was proposed as the cut-off level to predict clinical relevant-postoperative pancreatic fistula by the receiver operating characteristic curve. The sensitivity, specificity and accuracy of this level were respectively 84.6%, 88.9% and 88.5%. The multivariate logistic regression analysis revealed that intraoperative amylase value and suture closure for the pancreatic stump were the significant predictive risk factors for the clinical relevant-postoperative pancreatic fistula.

Conclusion

The intraoperative amylase value can be early and easily measured as a predictive risk factor, which seems useful for postoperative management of clinical relevant-postoperative pancreatic fistula after distal pancreatectomy. While, the stapler closure might be a feasible way for the pancreatic transection during the operation.

Rapid detection of papillary thyroid carcinoma by fluorescence imaging using a γ-glutamyltranspeptidase-specific probe: a pilot study

Background

Nodular lesions of the thyroid gland, including papillary thyroid carcinoma (PTC), may be difficult to diagnose by imaging, such as in ultrasonic echo testing, or by needle biopsy. Definitive diagnosis is made by pathological examination but takes several days. A more rapid and simple method to clarify whether thyroid nodular lesions are benign or malignant is needed. Fluorescence imaging with γ-glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) uses γ-glutamyltranspeptidase (GGT), a cell-surface enzyme, to hydrolyze the γ-glutamyl peptide and transfer the γ-glutamyl group. GGT is overexpressed in several cancers, such as breast, lung, and liver cancers. This imaging method is rapid and useful for detecting such cancers. In this study, we tried to develop a rapid fluorescence detection method for clinical samples of thyroid cancer, especially papillary carcinoma.

Methods

Fluorescence imaging with gGlu-HMRG was performed to detect PTC using 23 surgically resected clinical samples. A portable imaging device conveniently captured white-light images and fluorescence images with blue excitation light. Hematoxylin-eosin (HE) staining was used to evaluate which fluorescent regions coincided with cancer, and immunohistochemical examination was used to detect GGT expression.

Results

All 16 PTC samples exhibited fluorescence after topical application of gGlu-HMRG, whereas the normal sections of each sample showed no fluorescence. HE staining revealed that each fluorescent region corresponded to a region with carcinoma. The PTC samples also exhibited GGT expression, as confirmed by immunohistochemistry.

Conclusions

All PTC samples were detected by fluorescence imaging with gGlu-HMRG. Thus, fluorescence imaging with gGlu-HMRG is a rapid, simple, and powerful detection tool for PTC.

Advantages of patient-derived orthotopic mouse models and genetic reporters for developing fluorescence-guided surgery

Fluorescence-guided surgery can enhance the surgeon's ability to achieve a complete oncologic resection. There are a number of tumor-specific probes being developed with many preclinical mouse models to evaluate their efficacy. The current review discusses the different preclinical mouse models in the setting of probe evaluation and highlights the advantages of patient-derived orthotopic xenografts (PDOX) mouse models and genetic reporters to develop fluorescence-guided surgery.

The development of fluorescence guided surgery for pancreatic cancer: from bench to clinic

INTRODUCTION

Surgeons face major challenges in achieving curative R0 resection for pancreatic cancers. When the lesion is localized, they must appropriately visualize the tumor, determine appropriate resection margins, and ensure complete tumor clearance. Real-time surgical navigation using fluorescence-guidance has enhanced the ability of surgeons to see the tumor and has the potential to assist in achieving more oncologically complete resections. When there is metastatic disease, fluorescence enhancement can help detect these lesions and prevent unnecessary and futile surgeries. Areas covered: This article reviews different approaches for delivery of a fluorescence signal, their pre-clinical and clinical developments for fluorescence guided surgery, the advantages/challenges of each, and their potential for advancements in the future. Expert commentary: A variety of molecular imaging techniques are available for delivering tumor-specific fluorescence signals. Significant advancements have been made in the past 10 years due to the large body of literature on targeted therapies and this has translated into rapid developments of tumor-specific probes.

Pancreatic Compression during Lymph Node Dissection in Laparoscopic Gastrectomy: Possible Cause of Pancreatic Leakage

Purpose

Postoperative pancreatic fistula is a serious and fatal complication of gastrectomy for gastric cancer. Blunt trauma to the parenchyma of the pancreas can result from an assistant's forceps compressing and retracting the pancreas, which in turn may result in pancreatic juice leakage. However, no published studies have focused on blunt trauma to the pancreas during laparoscopic surgery. Our aim was to investigate the relationship between compression of the pancreas and pancreatic juice leakage in a swine model.

Materials and Methods

Three female pigs were used in this study. The pancreas was gently compressed dorsally for 15 minutes laparoscopically with gauze grasped with forceps. Pancreatic juice leakage was visualized by fluorescence imaging after topical administration of chymotrypsin-activatable fluorophore in real time. Amylase concentrations in ascites collected at specified times was measured. In addition, pancreatic tissue was fixed with formalin, and the histology of the compressed sites was evaluated.

Results

Fluorescence imaging enabled visualization of pancreatic juice leaking into ascites around the pancreas. Median concentrations of pancreatic amylase in ascites increased from 46 U/L preoperatively to 12,509 U/L 4 hours after compression. Histological examination of tissues obtained 4 hours after compression revealed necrotic pancreatic acinar cells extending from the surface to deep within the pancreas and infiltration of inflammatory cells.

Conclusions

Pancreatic compression by the assistant's forceps can contribute to pancreatic juice leakage. These findings will help to improve the procedure for lymph node dissection around the pancreas during laparoscopic gastrectomy.

Intra-Operative Amylase Concentration in Peri-Pancreatic Fluid Predicts Pancreatic Fistula After Distal Pancreatectomy

Post-operative pancreatic fistula (POPF) is a potentially severe complication following distal pancreatectomy. The aim of this study was to assess the predictive value of intra-operative amylase concentration (IOAC) in peri-pancreatic fluid after distal pancreatectomy for the diagnosis of POPF. Consecutive patients who underwent a distal pancreatectomy between November 2014 and September 2016 were included in the analysis. IOAC was measured, followed by drain fluid analysis for amylase on post-operative days (PODs) 1, 3, and 5. Receiver operator characteristic (ROC) analysis was performed to evaluate the discriminative capacity of IOAC as a predictor of POPF. IOAC was measured after distal pancreatectomy in 26 patients. The IOAC correlated significantly with (i) PODs 1, 3, and 5 drain amylase (p < 0.01); (ii) the development of POPF (p < 0.01); and (iii) the Clavien-Dindo grade of surgical complications (p = 0.02). Eighty-three percent of patients with an IOAC > 1000 experienced a post-operative complication (OR 18.3, 95% CI 2.51-103, p < 0.01). ROC curve analysis confirmed the predictive relationship of IOAC and POPF as an excellent test with an area under the curve of 0.92 (95% CI 0.81-0.99, p < 0.01). Measurement of IOAC allows early and accurate categorization of patients at risk for POPF in distal pancreatectomy.

Novel Bio-imaging Tools Based on the Precise Design of Functional Fluorescence Probes

Fluorescence imaging is one of the most powerful techniques currently available for continuous observation of intracellular processes in living cells and tissues, and so it would be useful to have a large toolset of fluorescence probes suitable for visualizing bioactive molecules or biological phenomena. However, design strategies for small molecule-based fluorescence probes have been limited. Therefore, we are interested in establishing novel rational design strategies for developing functional fluorescence probes. For this purpose, we have focused on the intramolecular spirocyclization reaction of rhodamine derivatives bearing intramolecular nucleophiles as a fluorescence switching mechanism; these derivatives exist in thermal equilibrium between a fluorescent open form and a non-fluorescent spirocyclic form. By utilizing this reaction, we have successfully developed various kinds of fluorescence probes. This review first describes the design of our recently developed fluorescence probes, and then introduces their applications for visualizing the activities of reporter enzymes, for in vivo cancer imaging, and for super-resolution imaging. We believe these probes can serve as key tools to provide unprecedented insights into a wide range of biological phenomena.