Use of a fluorescent bile acid to enhance visualization of the biliary tract and bile leaks during laparoscopic surgery in rabbits

Fluorescent 4-Nitrobenzo-2-oxa-1,3-diazole-Coupled Bile Acids as Probe Substrates of Hepatic and Intestinal Bile Acid Transporters of the Solute Carrier Families SLC10 and SLCO

Several bile acid (BA) transporters are involved in the enterohepatic BA circulation between the liver and gut, including the hepatic Na+/taurocholate cotransporting polypeptide (NTCP) and the intestinal apical sodium-dependent BA transporter (ASBT). Fluorescent BA derivatives are helpful to measure and visualize BA transport in vitro and in vivo. We used 4-nitrobenzo-2-oxa-1,3-diazole (NBD) as the labeling fluorophore and synthesized a series of 3-NBD-coupled BA. While 3α-NBD-taurocholic acid, 3β-NBD-taurocholic acid, 3α-NBD-glycocholic acid, and 3β-NBD-glycocholic acid showed significant transport rates for human NTCP, mouse mNtcp, and mouse mAsbt, human ASBT only showed reliable transport activity for 3α-NBD-glycocholic acid. In general, NBD coupling to the 3α-position proved superior to the 3β-position, and the NBD-BA with glycine conjugation exhibited the highest overall transport rates. None of the synthesized NBD-BA was transported by the organic anion transporting polypeptides OATP1B1 and OATP1B3. Overall, 3α-NBD-glycocholic acid is most appropriate for fluorescence-based transport assays to evaluate NTCP and ASBT inhibitors.

From shadow to light: visualization of extrahepatic bile ducts using image-enhanced laparoscopy

BACKGROUND

Correct recognition of the extrahepatic bile ducts is thought to be crucial to reduce the risk of bile duct injuries during various laparoscopic procedures. Image-enhanced laparoscopy techniques, utilizing various optical modalities other than white light, may help in detecting structures "hidden" underneath connective tissue.

METHODS

A systematic literature search was conducted of studies describing image-enhanced laparoscopy techniques for visualization of the extrahepatic bile ducts.

RESULTS

In all, 29 articles met inclusion criteria. They describe various techniques in the animal or human setting, including autofluorescence imaging, drug-enhanced fluorescence imaging, infrared thermography, and spectral imaging. This review describes these various techniques and their results.

CONCLUSION

Image-enhanced laparoscopy techniques for real-time visualization of extrahepatic bile ducts are still in its infancy. Out of the techniques currently described, indocyanine green-enhanced near-infrared fluorescence laparoscopy has the most mature results, but other techniques also appear promising. It can be expected that in the future, image-enhanced laparoscopy might become a routine adjunct to any white-light laparoscopic operation near the hepatic hilum.

Advanced intraoperative imaging methods for laparoscopic anatomy navigation: an overview

BACKGROUND

Safety and efficiency are important topics in minimally invasive surgery. Apart from its advantages, laparoscopic surgery has the following drawbacks: two-dimensional imaging, challenging eye-hand coordination, and absence of tactile feedback. Enhanced imaging with earlier and clearer identification of essential tissue types can partly overcome these disadvantages. Research groups worldwide are investigating new technologies for image-guided surgery purposes. This review article gives an overview of current developments in surgical optical imaging for improved anatomic identification and physiologic tissue characterization during laparoscopic gastrointestinal surgery.

METHODS

A systematic literature search in the PubMed database was conducted. Eligible studies reported on any kind of novel optical imaging technique applied for anatomic identification or physiologic tissue characterization in laparoscopic gastrointestinal surgery. Gynecologic and urologic procedures also were included whenever vascular, nerve, ureter, or lymph node imaging was concerned.

RESULTS

Various surgical imaging techniques for enhanced intraoperative visualization of essential tissue types (i.e., blood vessel, bile duct, ureter, nerve, lymph node) and for tissue characterization purposes such as assessment of blood perfusion were identified. An overview of preclinical and clinical experiences is given as well as the potential added value for intraoperative anatomic localization and characterization during laparoscopy.

CONCLUSION

Implementation of new optical imaging methods during laparoscopic gastrointestinal surgery can improve intraoperative anatomy navigation. This may lead to increased patient safety (preventing iatrogenic functional tissue injury) and procedural efficiency (shorter operating time). Near-infrared fluorescence imaging seems to possess the greatest potential for implementation in clinical practice in the near future.

Fluorescence-guided laparoscopic cholecystectomy: a new technique for visualization of biliary system by using fluorescein

BACKGROUND

Safe cholecystectomy requires confident identification of extrahepatic biliary anatomy. This is the first report of the use of fluorescein and ultraviolet light to improve visualization of biliary topography during laparoscopic cholecystectomy.

METHODS

Five patients who had symptomatic gallstones underwent laparoscopic cholecystectomy with intraoperative intravenous fluorescein injection. Ultraviolet A from an LED light source was used to induce fluorescence of bile. It was delivered by a device that was designed and built by the authors.

RESULTS

Within 4 to 5 minutes the bile ducts were shining with green fluorescence and were easily differentiated from the surrounding tissues. In all cases, identification of the extrahepatic biliary anatomy by the fluorescence technique preceded its identification with conventional white light. Fluorescence remained for the whole duration of operation that extended for 42 to 77 minutes.

CONCLUSIONS

At laparoscopic cholecystectomy, intravenous fluorescein injection and ultraviolet A excitation induce bile ducts to fluoresce. The technique allows better and earlier real-time visualization of biliary anatomy than conventional white light. The technique is simple and inexpensive. It serves as an additional tool that would improve safety of laparoscopic cholecystectomy.

Intraoperative near-infrared fluorescent cholangiography (NIRFC) in mouse models of bile duct injury

BACKGROUND

Accidental injury to the common bile duct is a rare but serious complication of laparoscopic cholecystectomy. Accurate visualization of the biliary ducts may prevent injury or allow its early detection. Conventional X-ray cholangiography is often used and can mitigate the severity of injury when correctly interpreted. However, it may be useful to have an imaging method that could provide real-time extrahepatic bile duct visualization without changing the field of view from the laparoscope. The purpose of the present study was to test a new near-infrared (NIR) fluorescent agent that is rapidly excreted via the biliary route in preclinical models to evaluate intraoperative real-time near infrared fluorescent cholangiography (NIRFC).

METHODS

To investigate probe function and excretion, a lipophilic near-infrared fluorescent agent with hepatobiliary excretion was injected intravenously into one group of C57/BL6 control mice and four groups of C57/BL6 mice under the following experimentally induced conditions: (1) chronic biliary obstruction, (2) acute biliary obstruction (3) bile duct perforation, and (4) choledocholithiasis, respectively. The biliary system was imaged intravitally for 1 h with near-infrared fluorescence (NIRF) with an intraoperative small animal imaging system (excitation 649 nm, emission 675 nm).

RESULTS

The extrahepatic ducts and extraluminal bile were clearly visible due to the robust fluorescence of the excreted fluorochrome. Twenty-five minutes after intravenous injection, the target-to-background ratio peaked at 6.40 +/- 0.83 but signal was clearly visible for ~60 min. The agent facilitated rapid identification of biliary obstruction and bile duct perforation. Implanted beads simulating choledocholithiasis were promptly identifiable within the common bile duct lumen.

CONCLUSIONS

Near-infrared fluorescent agents with hepatobiliary excretion may be used intraoperatively to visualize extrahepatic biliary anatomy and physiology. Used in conjunction with laparoscopic imaging technologies, the use of this technique should enhance hepatobiliary surgery.

Real-time intra-operative near-infrared fluorescence identification of the extrahepatic bile ducts using clinically available contrast agents

BACKGROUND

Iatrogenic bile duct injuries are serious complications with patient morbidity. We hypothesized that the invisible near-infrared (NIR) fluorescence properties of methylene blue (MB) and indocyanine green (ICG) could be exploited for real-time, intraoperative imaging of the extrahepatic bile ducts during open and laparoscopic surgeries.

METHODS

In all, 2.0 mg/kg of MB and 0.05 mg/kg of ICG were injected intravenously into 35-kg female Yorkshire pigs and the extrahepatic bile ducts were imaged over time using either the Fluorescence-Assisted Resection and Exploration (FLARE) image-guided surgery system (open surgery) or a custom NIR fluorescence laparoscopy system. Surgical anatomy was confirmed using x-ray cholangiography. The contrast-to-background ratio (CBR), contrast-to-liver ratio (CLR), and chemical concentrations in the cystic duct (CD) and common bile duct (CBD) were measured, and the performance of each agent was quantified.

RESULTS

Using NIR fluorescence of MB, the CD and CBD could be identified with good sensitivity (CBR and CLR > or =4), during both open and laparoscopic surgeries, from 10 to 120 min postinjection. Functional impairment of the ducts, including constriction and injury were immediately identifiable. Using NIR fluorescence of ICG, extrahepatic bile ducts did not become visible until 90 min postinjection because of strong residual liver retention; however, between 90 and 240 min, ICG provided exquisitely high sensitivity for both CD and CBD, with CBR > or =8 and CLR > or =4.

CONCLUSION

We demonstrate that 2 clinically available NIR fluorophores, MB fluorescing at 700 nm and ICG fluorescing at 800 nm, provide sensitive, prolonged identification of the extrahepatic bile ducts and assessment of their functional status.

[Laparoscopic vesical autoaugmentation: an animal model in rabbits (Oryctolagus cuniculus)]

INTRODUCTION

Small contracted bladder remains a challenge in clinical urological practice and treatment options are not always effective. Urothelium sparing surgical techniques represent a reasonable therapeutical option. We aimed to evaluate the feasibility of a rabbit model (Oryctolagus cuniculus) in the teaching and training setting for laparoscopic vesical autoaugmentation.

METHODS

Transperitoneal laparoscopic bladder autoaugmentation was performed in five New Zealand male rabbits (Oryctolagus cuniculus). A three port technique was used for all cases. Circumferential detrusorectomy was performed with vascular pedicles sparing, subsequently submucosal detailed blunt dissection allowed the creation of a bladder diverticulum which was verified intraoperatively. Eye-ball cystometry was performed preoperatively and postoperatively to verify bladder capacity variations. Postoperatively cystometry was done immediately after the procedure and 7 and 15 days postoperatively. Statistical analysis was performed with T-student model. A p-value < 0.05 was considered of significance for the analysis. Surgical procedure and perioperative animal care was minutely precised according to the Guidelines of the Institute of Laboratory Animal Resources, Commission on Life Sciences, National Research Council.

RESULTS

Five New Zealand male rabbits (Oryctolagus cuniculus) were surgically treated as described. Median operative time was 68.8 minutes (range 44 -120). Median preoperatory bladder capacity for the series was 25.8 cc (7-52). Median postoperative bladder capacity was diminished in 33% immediately after the operation. Then, bladder capacity augmented 72% and 52% for 7th and 15th postoperative days, respectively. Percentage variation in bladder capacity is statistically significant. Two operative complications (mucosal tear) were reported. A postoperatory abscess was observed in one animal.

CONCLUSION

The rabbit (Oryctolagus cuniculus) model for the laparoscopic bladder autoaugmentation is feasible for teaching, training and research. Bigger series and longer follow-up should be addressed.

Fluorescent cholangiography in a mouse model: an innovative method for improved laparoscopic identification of the biliary anatomy

BACKGROUND

Real-time imaging of the biliary anatomy may facilitate safe and timely completion of laparoscopic cholecystectomy. This study sought to determine whether the unique autofluorescent properties of bile could facilitate intraoperative identification of the biliary anatomy in mice using fluorescent cholangiography.

METHODS

Fluorimetry was performed on samples of mouse bile to determine excitation and emission spectra. For seven mice, chevron laparotomy was performed, followed by liver retraction to expose the porta hepatis. Using stereomicroscopy, photographs were taken in brightfield and fluorescent modes without a change in depth or focus. Six surgical residents evaluated the pictures and identified the gallbladder, cystic duct, common bile duct, and whether the cystic duct joined the right hepatic duct or the common bile duct.

RESULTS

Fluorimetry demonstrated autofluorescence of bile at an excitation wavelength of 475 nm. Intense emission was observed at 480 nm. At these settings, fluorescent stereomicroscopy easily identified the gallbladder and biliary tree in mice. This technique decreased diagnostic errors of the biliary anatomy 11-fold (2% vs 22%; p < 0.01), as compared with brightfield visualization. Fluorescent stereomicroscopy also was used to diagnose bile leak, obstruction, and complex anatomy. Using a prototype 5-mm laparoscope equipped with fluorescent filters, the results were reproduced.

CONCLUSIONS

Fluorescent cholangiography based solely on the autofluorescence of bile may facilitate real-time identification of the biliary anatomy during laparoscopic procedures, without the need for extraneous dye administration or the use of radiography. This technique has the potential to decrease the rate of iatrogenic biliary tract injuries during laparoscopic cholecystectomy.