Endoscopic direct cholangioscopy by using an ultra-slim upper endoscope: a feasibility study

The Role of Cholangioscopy in Biliary Diseases

Endoscopy plays a central role in diagnostic and therapeutic approaches to biliary disease in both benign and malignant conditions. A cholangioscope is an endoscopic instrument that allows for the direct exploration of the biliary tree. Over the years, technology has improved endoscopic image quality and allowed for the development of an operative procedure that can be performed during cholangioscopy. Different types of instruments are available in this context, and they can be used in different anatomical access points according to the most appropriate clinical indication. The direct visualization of biliary mucosa is essential in the presence of biliary strictures of unknown significance, allowing for the appropriate allocation of patients to surgery or conservative treatments. Cholangioscopy has demonstrated excellent performance in discriminating malignant conditions (such as colangiocarcinoma) from benign inflammatory strictures, and more recent advances (e.g., artificial intelligence and confocal laser endomicroscopy) could further increase its diagnostic accuracy. Cholangioscopy also plays a primary role in the treatment of benign conditions such as difficult bile stones (DBSs). In this case, it may not be possible to achieve complete biliary drainage using standard ERCP. Therapeutic cholangioscopy-guided lithotripsy allows for stone fragmentation and complete biliary drainage. Indeed, other complex clinical situations, such as patients with intra-hepatic lithiasis and patients with an altered anatomy, could benefit from the therapeutic role of cholangioscopy. The aim of the present review is to explore the most recent diagnostic and therapeutic advances in the roles of cholangioscopy in the management of biliary diseases.

A Preliminary Study on the Efficacy of Single-Operator Cholangioscopy with a New Basket for Residual Stone Retrieval After Mechanical Lithotripsy

BACKGROUND AND AIM

The detection of residual or fragmented common bile duct (CBD) stones after lithotripsy can be improved by the high-resolution imaging quality of digital, single-operator cholangioscopy (SOC). However, therapeutic interventions for the removal of residual CBD stones are limited by the lack of appropriate tools. We retrospectively evaluated the role of SOC and the newly developed Dormia basket for the evaluation and removal of stones remaining after lithotripsy.

METHODS

Thirty-four patients who had undergone lithotripsy for retained CBD stones with no evidence of filling defects in occluded balloon cholangiography from March 2017 to October 2018 were included in the study. After balloon cholangiography, the bile duct was evaluated by SOC for complete evacuation of the stones. The detected residual CBD stones were directly retrieved by inserting the newly developed Dormia basket into the working channel of the SOC. The incidence of residual stones detected by SOC and the success rate of residual stone retrieval by SOC were investigated.

RESULTS

Digital SOC was successfully performed in all patients. Of these, 11 patients (32.4%) had residual CBD stones. The residual stones were successfully removed in 10 patients (90.9%) by SOC using the Dormia basket, except in one case of residual stones left in the hepatic duct. There were no adverse events associated with the SOC procedures or direct stone removal.

CONCLUSIONS

Digital SOC combined with the newly developed Dormia basket was useful for the detection and extraction of residual CBD stones under direct visualization after lithotripsy.

Advanced Imaging of the Biliary System and Pancreas

Despite advances in noninvasive techniques for imaging the pancreaticobiliary system, several disease processes including indeterminate biliary strictures as well as neuroendocrine tumors, inflammatory pseudotumors, and complex cysts of the pancreas remain difficult to characterize. New endoscopic imaging technologies have emerged to address these challenges. Cholangioscopy and intraductal ultrasound (IDUS) are powerful tools to characterize subtle biliary concretions and strictures. Confocal Laser Endomicroscopy (CLE) and Optical Coherence Tomography (OCT) are emerging approaches for the most difficult biliary lesions. Contrast harmonic endoscopic ultrasound (CH-EUS), elastography, and 3D-EUS are improving the approach to subtle pancreatic lesions, particularly in the context of indeterminate tissue sampling. Pancreatoscopy, pancreatic IDUS, and intracystic CLE hold promise to further improve the assessment of pancreatic cysts. We aim to comprehensively review the emerging clinical evidence for these innovative endoscopic imaging techniques.

Peroral cholangioscopy: Update on the state-of-the-art

Peroral cholangioscopy (POC) is an endoscopic procedure that allows direct intraductal visualization of the biliary tract. POC has emerged as a vital tool for indeterminate biliary stricture evaluation and treatment of difficult biliary stones. Over several generations of devices, POC has fulfilled additional clinical needs where other diagnostic or therapeutic modalities have been inadequate. With adverse event rates comparable to standard endoscopic retrograde cholangioscopy and unique technical attributes, the role of POC is likely to continue expand. In this frontiers article, we highlight the existing and growing clinical applications of POC as well as areas of ongoing research.

Utility of Direct Peroral Cholangioscopy Using a Multibending Ultraslim Endoscope for Difficult Common Bile Duct Stones

Background/Aims

Treatment options for difficult bile duct stones are limited. Direct peroral cholangioscopy (POC)-guided lithotripsy may be an option. A newly developed multibending (MB) ultraslim endoscope has several structural features optimized for direct POC. We evaluated the utility of direct POC using an MB ultraslim endoscope for lithotripsy in patients with difficult bile duct stones.

Methods

Twenty patients with difficult bile duct stones, in whom stone removal using conventional endoscopic methods, including mechanical lithotripsy, had failed were enrolled from March 2018 to August 2019. Direct POC-guided lithotripsy was performed by electrohydraulic lithotripsy or laser lithotripsy. The primary outcome was complete ductal clearance, defined as the retrieval of all bile duct stones after lithotripsy confirmed by balloon-occluded cholangiography and/or direct POC.

Results

The technical success rate of direct POC was 100% (20/20), and the free-hand insertion rate was 95% (19/20). Direct POC-guided lithotripsy, attempted by electrohydraulic lithotripsy in nine patients (45%) and laser lithotripsy in 11 patients (55%), was successful in 95% (19/20) of the patients. Complete ductal clearance after direct POC-guided lithotripsy was achieved in 95% (19/20) of patients. Patients required a median of 2 (range, 1-3) endoscopic retrograde cholangiopancreatography sessions for complete stone removal. Adverse event was observed in one patient (5%) with hemobilia and was treated conservatively.

Conclusions

Direct POC using an MB ultraslim endoscope was safe and effective for lithotripsy in patients with difficult bile duct stones.

Cracking Difficult Biliary Stones

Apart from difficult biliary cannulation, biliary stone removal is considered one of the hurdles in endoscopic retrograde cholangiopancreatography. Generally, simple common bile duct (CBD) stones can be removed either with an extraction balloon or a basket. However, there are difficult stones that cannot be removed using these standard methods. The most difficult stones are large CBD stones and impacted stones in a tapering CBD. A few decades ago, mechanical lithotripsy was usually required to manage these stones. At present, endoscopic papillary large balloon dilation (EPLBD) of the biliary orifice has become the gold standard for large CBD stones up to 1.5 cm. EPLBD can reduce the procedural time by shortening the stone removal process. It can also save the cost of the devices, especially multiple baskets, used in mechanical lithotripsy. Unfortunately, very large CBD stones, stones impacted in a tapering CBD, and some intrahepatic duct stones still require lithotripsy. Peroral cholangioscopy provides direct visualization of the stone, which helps the endoscopist perform a probe-based lithotripsy either with an electrohydraulic probe or a laser probe. This technique can facilitate the management of difficult CBD stones with a high success rate and save procedural time without significant technical complications.

Novel peroral cholangioscopy-directed lithotripsy using an ultraslim upper endoscope for refractory Mirizzi syndrome: A case report

RATIONALE

Mirizzi syndrome (MS) is an uncommon condition characterized by common hepatic duct (CHD) compression by an impacted gallbladder or cystic duct stones or adjacent inflammation. To date, a standardized therapeutic strategy for MS has not been established yet, owing to its complex clinical presentation. Thus, researchers still have to develop new optimized approaches to solve this problem. Herein, we describe a patient with refractory MS who underwent a successful treatment by novel hybrid anchoring balloon-guided direct peroral cholangioscopy (POC) using an ultraslim endoscope.

PATIENT CONCERNS

A 56-year-old man with a history of biliary stone was referred to our hospital for complaints of discomfort in the right upper quadrant of the abdomen and obstructive jaundice. Endoscopic retrograde cholangiopancreatography showed an 18-mm impacted stone at the level of the cystic duct, which compressed the CHD. The CHD had local stricture, with its upstream and intrahepatic bile duct dilation.

DIAGNOSES

He was diagnosed with type I MS.

INTERVENTIONS

Initially, the patient received an endoscopic major sphincterotomy. However, conventional stone extraction, including mechanical lithotripsy, was unsuccessful. Then, after signing the informed consent form for further treatment, he was successfully treated with novel hybrid anchoring balloon-guided direct POC.

OUTCOMES

The patient had no operative complications and was discharged with cleared ducts. At the 3-year follow-up, he was asymptomatic.

LESSONS

Our novel hybrid anchoring balloon-guided direct POC may be an effective alternative treatment approach for difficult gallbladder cases, such as refractory MS.

Clinical value of DPOC for detecting and removing residual common bile duct stones (video)

Background

This study aims to evaluate the efficacy and safety of detecting and removing residual common bile duct stones (CBDS) using direct peroralcholangioscopy (DPOC) after performing endoscopic retrograde cholangiopancreatography (ERCP) for stone retrieval.

Methods

From January 5, 2017 to December 27, 2017, a total of 164 cases of choledocholithiasis were treated by ERCP for stone retrieval. According to the inclusion and exclusion criteria, the remaining 79 cases (39 males; mean age: 63.3 years old, range: 52–79 years old) were enrolled in the present study. The maximum transverse stone diameter was 6–15 mm (12.7 ± 4.2 mm), as determined by ERCP. Furthermore, there were 57 cases of multiple stones (number of stones: two in 41 cases, three in nine cases, and ≥ 4 in seven cases), 13 cases of post-mechanical lithotripsy, and nine cases of broken stones.

Results

The overall success rate of DPOC was 94.9% (75/79). Furthermore, 18.7%(14/75) of cases were directly inserted, 72%(54/75) of cases required guide wire assistance, and 9.3%(7/75) of cases were successfully inserted with overtube assistance. The average insertion time was 7–17 min (4.9 ± 2.9 min). Residual stones were detected in 19 cases (25.3%), and all of which were < 5 mm in diameter. Moreover, five cases of formed stones were removed by basket and balloon catheter, while the remaining cases were cleaned after irrigation and suction. There were no serious complications.

Conclusion

DPOC is safe and effective for both the detection and removal of residual CBDS after conventional ERCP.

Electronic supplementary material

The online version of this article (10.1186/s12876-019-1045-6) contains supplementary material, which is available to authorized users.

Advances in Endoscopic Imaging of the Biliary Tree

Direct endoscopic imaging of the biliary tree is increasingly performed by endoscopists since the introduction of digital single-operator cholangioscopy. In parallel, there have been several advances to overcome the challenges associated with direct peroral cholangioscopy with development of multibending cholangioscopes and new devices to enable direct placement of an endoscope into the biliary tree without a supporting duodenoscope. The indications for cholangioscopy are also evolving with newer indications, such as intraductal lithotripsy, foreign body (mostly stent) removal, guide wire cannulation of specific ducts, photodynamic therapy for cholangiocarcinoma, and performance of fluoroscopy-free cholangiography. There has also been progress in image enhancement during cholangioscopy and additional imaging techniques, such as intraductal ultrasound, confocal laser endomicroscopy, and optical coherence tomography.

Clinical study of the use of gastroscopy as oral choledochoscopy

Clinical value and safety of the use of gastroscopy as oral choledochoscopy in the treatment of biliary diseases was explored. Clinical data of 55 patients with biliary diseases who underwent gastroscopy were retrospectively analyzed. The types of gastroscopy, size of duodenal papilla incision, balloon dilatation, the success rate of gastroscopy entry, depth of gastroscopy entering into bile duct, endoscopic diagnosis and postoperative complications were recorded. Simple insertion-by-hand was performed, and insertion into common bile duct was successfully achieved in 53 cases, and the overall technical success rate was 96.4%. Residual bile duct stones in 25 patients (45.5%) after endoscopic retrograde cholangio-pancreatography (ERCP) were removed through endoscopy. Nine cases of benign stenosis and 2 cases of malignant stenosis were confirmed as ‘cholangiocarcinoma’ or ‘duodenal papilla well-differentiated adenocarcinoma’ by biopsy. Balloon oppression under intraoperative endoscopy was performed for 2 cases (3.6%) with biliary hemorrhage, and argon ion coagulation was successfully performed. No obvious abnormalities were found in 13 cases (23.6%) through gastroscopic biliary exploration. Complications occurred in 15 patients with a complication rate of 27.3%, including 2 cases of cholecystitis (3.6%), 8 cases of amyloidosis (14.6%) and 4 cases of acute pancreatitis (7.3%), and all those complications were cured. One case (1.8%) had perforation of biliary tract and was discharged after conservative treatment. The use of gastroscopy as oral choledochoscopy is safe as effective. However, this technique causes some rare and serious complications. Therefore, further studies are needed to improve this technique.

A new hybrid anchoring balloon for direct peroral cholangioscopy using an ultraslim upper endoscope

BACKGROUND AND AIM

Large impacted or residual invisible common bile duct (CBD) stones after mechanical lithotripsy are challenging. We aimed to evaluate the feasibility and success rate of a new hybrid anchoring balloon-guided direct peroral cholangioscopy (POC) for these conditions using an ultraslim endoscope.

METHODS

Sixty-five patients with large or residual invisible CBD stones for direct POC from July 2012 to July 2016 were identified, including six cases in whom an additional interventional procedure was required. There were altogether 55 cases undergoing a procedure with our new device, with a 0.021-inch guidewire tied to a balloon catheter at its distal end in this single-center retrospective study. Technical success, procedure time, diagnostic and therapeutic efficacy of direct POC, and procedure-related complications were studied.

RESULTS

The hybrid anchoring balloon-guided direct POC was successful in 51/55 (92.7%) procedures, including 18 cases in whom the conventional wire-guided method failed within 25 min. Mean time for technical success by our method was 12.4 ± 3.4 min. In total, of the 43 cases with previous removal of CBD stones, seven (16.3%) were found to have residual stones ≥4 mm, excluding three cases in whom direct POC failed. In another 25 cases for difficult stones, 24 lithotripsies were carried out, resulting in 23 complete fragmentations. No significant procedure-related complications were observed.

CONCLUSION

The new hybrid anchoring balloon device performs well in facilitating direct POC using an ultraslim endoscope for evaluation and extraction of residual or large impacted CBD stones.

Indeterminate biliary strictures: a simplified approach

Pre-operative evaluation of biliary strictures remains challenging. The dilemma that exists is how to balance the risk of failing to detect malignancy and the potential morbidity caused by unnecessary surgery in patients with benign etiologies. With emerging novel diagnostic modalities, this study aims to assess the efficacy of diagnostic techniques and facilitate a clinical approach to indeterminate biliary strictures. Areas covered: Conventional imaging modalities are crucial in identifying the location of a stricture and are helpful for choosing further diagnostic modalities. Utilization of endoscopic techniques, including endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound (EUS), is key in establishing a diagnosis. The emergence of novel diagnostic modalities, such as fluorescence in-situ hybridization (FISH), peroral cholangioscopy (POC), intraductal endoscopic ultrasound (IDUS) and confocal laser endomicroscopy (CLE), enhance the diagnostic yield in the evaluation of indeterminate biliary strictures. Expert commentary: More reliable and validated visual criteria for differentiating malignancy from benign biliary conditions, utilizing advanced imaging modalities such as POC and CLE, need to be established. It is of significance to further evaluate these novel diagnostic modalities through ongoing trials and to develop a diagnostic algorithm that reconciles cost-effectiveness with diagnostic accuracy.

Novel ex vivo training model for freehand insertion using a double-bending peroral direct cholangioscope

BACKGROUND AND AIM

Several experts of direct peroral videocholangioscopy (D-PVCS) using a conventional ultraslim endoscope have reported its usefulness for the diagnosis and therapy of biliary tract diseases. We have additionally developed a dedicated double-bending D-PVCS technique for freehand scope insertion. In this study, we developed an ex vivo training model for the freehand double-bending D-PVCS technique and compared it with the technique using a conventional ultraslim endoscope.

METHODS

The ex vivo model was made for training using a U-shape insertion pattern. A third prototype endoscope and an ultraslim upper gastrointestinal endoscope were used. Two experts and nine non-experts performed D-PVCS using the freehand technique.

RESULTS

The two experts could not advance the tip of the endoscope to the hilar portion using the freehand technique, but they could achieve technical successful insertion to the hilar portion with the third prototype cholangioscope using the freehand technique alone. The non-experts could not advance the tip of the endoscope to the bile duct using the freehand technique. On the other hand, two (22.2%) non-experts could advance the tip of the third prototype cholangioscope using the freehand technique before the training conducted by the experts. After the training, all the non-experts could advance the tip of the third prototype cholangioscope to the hilar portion.

CONCLUSIONS

The novel ex vivo model using a third prototype cholangioscope was useful for training in the use of the freehand D-PVCS technique.

Novel biomarkers and endoscopic techniques for diagnosing pancreaticobiliary malignancy

The UK incidence of pancreatic ductal adenocarcinoma is 9 per 100,000 population, and biliary tract cancer occurs at a rate of 1–2 per 100,000. The incidence of both cancers is increasing annually and these tumours continue to be diagnosed late and at an advanced stage, limiting options for curative treatment. Population-based screening programmes do not exist for these cancers, and diagnosis currently is dependent on symptom recognition, but often symptoms are not present until the disease is advanced. Recently, a number of promising blood and urine biomarkers have been described for pancreaticobiliary malignancy and are summarised in this review. Novel endoscopic techniques such as single-operator cholangioscopy and confocal endomicroscopy have been used in some centres to enhance standard endoscopic diagnostic techniques and are also evaluated in this review.

A snare-assisted peroral direct choledochoscopy and pancreatoscopy using an ultra-slim upper endoscope: A case series study

OBJECTIVE

To evaluate the feasibility, effectiveness and safety of a new snare-assisted peroral direct choledochoscopy/pancreatoscopy (PDCPS) technique.

METHODS

From November 2014 through December 2016, 20 consecutive patients with indications for PDCPS were enrolled in this observational study. Endoscopic retrograde cholangiography was initially performed using a conventional duodenoscope, and endoscopic papillary balloon dilation was performed. Next, an ultra-slim endoscope was inserted to perform the PDCPS; a snare tightened around the end of the scope's bending section facilitated its entry into the common bile duct (CBD). The primary endpoint was the overall success rate of the PDCPS procedure (successful biliary intubation and visualization of the area of interest) and the time for biliary intubation with the ultra-slim upper endoscope.

RESULTS

Participants (11 men and 9 women; mean age, 72.2 years [range, 41-93 years]) had CBD adenoma (n=1), large CBD stones after failed extraction/lithotripsy treatment (n=13), CBD strictures (n=4), pancreatic duct tumor (n=1) or pancreatic duct dilation (n=1). The success rate was 95%. The mean intubation time was 18min (range, 4-57min). No adverse events were reported.

CONCLUSIONS

A snare-assisted PDCPS technique appears to be technically feasible, effective and safe for both diagnostic and therapeutic applications.

Prospective evaluation of the short access cholangioscopy for stone clearance and evaluation of indeterminate strictures

BACKGROUND

Peroral cholangioscopy facilitates diagnosis and therapy of biliary disorders. This study prospectively evaluated a new short access cholangioscopy.

METHODS

Consecutive patients were included as follows: difficult stones (group 1) underwent cholangioscopy with electrohydraulic lithotripsy and indeterminate biliary strictures (group 2) were evaluated with macroscopic assessment and cholangioscopy guided biopsy sampling. We evaluated the complete stone clearance rate (group 1) and diagnostic accuracy (group 2). Follow-up was performed over a median of 13 and 16 months, respectively.

RESULTS

Group 1 (n=21): complete stone clearance defined as lack of stones in cholangiography and stone removal during cholangioscopy was achieved in 15 (71.4%) patients. Clinical stone clearance defined as lack of symptoms, laboratory abnormalities and hospital visits during follow-up, irrespective of stone clearance was evident in 17 (81.0%) patients. One serious adverse event occurred (bile duct perforation). Group 2 (n=28): malignancy was confirmed in 15 patients. Sensitivity, specificity and diagnostic accuracy of cholangioscopy were 85.7%, 75.0% and 80.7%, respectively. Sensitivity, specificity and diagnostic accuracy of biopsies were 54.5%, 100.0% and 72.2%, respectively. No serious adverse events occurred, and one patient was lost to follow-up.

CONCLUSIONS

The novel system enabled complex stone treatment and biliary stricture diagnosis. Cholangioscopy outperformed direct biopsy regarding characterization of indeterminate strictures.

Effects of carbon dioxide insufflation during direct cholangioscopy on biliary pressures and vital parameters: a pilot study in porcine models

BACKGROUND AND AIMS

Direct per-oral cholangioscopy allows endoscopic visualization of the biliary tract. Insufflation with carbon dioxide (CO₂) is an alternative to saline solution irrigation during direct cholangioscopy. There are no data on maximal CO₂ insufflation in direct cholangioscopy without causing biliary barotrauma or fatal gas embolism. We aimed to evaluate the safety of increasing CO₂ insufflation in direct cholangioscopy without causing biliary barotrauma or fatal gas embolism.

METHODS

This was an in vivo animal study. Four domestic pigs, under general endotracheal anesthesia, were used. The first animal was used to validate the feasibility of direct cholangioscopy and biliary pressure measurements, after which all animals underwent laparotomy, insertion of a pressure transducer in the cystic duct, and direct transpapillary placement of the cholangioscope. The common bile duct (CBD) and cystic duct were ligated to contain the instilled gas and exclusively expose the biliary tree. Insufflation of CO₂ started at 200 mL/min and was continuously increased until there was evidence of bile duct rupture (as measured by a drop in intraductal pressures) or instability of vital signs (hypotension, bradycardia, bradypnea, O₂ desaturation). Necropsy was performed on all animals to assess the liver and biliary system for evidence of barotrauma.

RESULTS

CO₂ was insufflated up to 8 L/min without causing bile duct rupture or instability in vital signs despite increasing CBD pressure with insufflation. There was significant correlation between CO₂ flow with partial pressure of CO₂ in arterial blood (PaCO₂) (coefficient, 0.96-1.00; P < .01) and end tidal expired CO₂ (EtCO₂) (coefficient, 0.94-1.00; P < .01). However, the pulse rate, respiratory rate, arterial blood pressure, and O₂ did not correlate with the amount of CO₂ flow. There was no evidence of hepatic or biliary barotrauma on necropsy.

CONCLUSIONS

This pilot experience in porcine models suggests that CO₂ insufflation is safe for direct cholangioscopy and does not result in biliary barotrauma or vital signs instability.

Dilation of Strictures in Patients with Inflammatory Bowel Disease: Who, When and How

Stricture formation occurs in up to 40% of patients with inflammatory bowel disease (IBD). Patients are often symptomatic, resulting in significant morbidity, hospitalizations, and loss of productivity. Strictures can be managed endoscopically in addition to traditional surgical management (sphincteroplasty or resection of the affected bowel segments). About 3% to 5% patients with IBD develop primary sclerosing cholangitis (PSC), which results in stricture formation in the biliary tree, managed for the most part by endoscopic therapies. In this article, we discuss endoscopic management of strictures both in the alimentary tract and biliary tree in patients with IBD and/or PSC.

Development of an in vivo swine model of biliary dilatation-based direct peroral cholangioscopy

A reproducible in vivo swine model of bile duct dilation (BDD) was recently established and reported for preclinical testing of newly developed biliary devices or endoscopic techniques. The aim of the present study was to develop a more advanced large animal model in which it is possible to direct examination of the biliary tree. Methods Six mini pigs were prepared for the study. BDD models were first made by closure of the Vater's ampulla in all swine. Then endoscopic papillary balloon dilation (EPBD) was done in the animals. Feasibility of single-operator peroral cholangioscopy without assistance of accessories was evaluated using an ultra-slim upper endoscope in the animals. Results EPBD could be implemented using a dilation balloon catheter (10~13.5 mm) in all BDD models (6/6, 100%). Success rate of freehand direct insertion of an ultra-slim endoscope into the common bile duct was 100% (6/6), and access to the common hepatic duct with examination was possible using direct peroral cholangioscopy in five animals (5/6, 83.3%). None of the animals died. In the cholangioscopic examination, a bile duct polyp and a benign biliary stricture occurred naturally, respectively, in two of the six swine. Conclusion An in vivo swine model of biliary dilatation-based direct peroral cholangioscopy was established. This novel animal model may be useful for preclinical research of new materials or devices because direct visualization of the biliary tree is feasible.

Recent developments in choledochoscopy: technical and clinical advances

Peroral cholangioscopy has become an important tool in the diagnosis and treatment of a variety of biliary diseases, ranging from indeterminate biliary strictures to bile duct stones. Although the first cholangioscopy was performed in the 1970s, recent technological advances have provided us with cholangioscopes that yield high-resolution images, possess single-operator capability, and have ultrathin design to allow easier maneuverability and detailed imaging of the biliary tract. We review here the currently available devices for peroral cholangioscopy, their clinical applications, limitations, and complications.

A newly modified access balloon catheter for direct peroral cholangioscopy by using an ultraslim upper endoscope (with videos)

BACKGROUND AND AIMS

Direct peroral cholangioscopy (POC) by using an ultraslim upper endoscope has been increasingly applied for diagnosis and treatment of diverse biliary diseases. Recently, an intraductal balloon catheter has been used commonly to guide the flexible ultraslim endoscope. However, accessibility into the bile duct remains a limitation of the procedure. The aim of this study was to evaluate the feasibility and success rate of an intraductal balloon-guided direct POC by using an ultraslim endoscope with a newly modified 5F balloon catheter.

METHODS

In total, 36 patients with biliary obstruction were included prospectively for a direct POC by using an ultraslim endoscope with a newly modified intraductal 5F balloon catheter. The main outcome measure was technical success, defined as successful advancement of the ultraslim endoscope into the obstructed segment of the biliary tree or the bifurcation. Secondary outcomes were mean time for the total procedure, intubation into the common bile duct and advancement up to the target site after intubation of the ultraslim endoscope, technical success rates of diagnostic and therapeutic interventions, and adverse events.

RESULTS

The intraductal balloon-guided direct POC using a newly modified 5F balloon catheter was completed successfully in 35 of 36 patients (97.2%). The mean times for total procedure, intubation into the distal common bile duct, and advancement up to the obstructed bile duct segment were 27.3 ± 7.2, 2.2 ± 0.5, and 0.8 ± 0.4 minutes, respectively. In total, 49 interventions were performed in 35 patients, excluding 1 patient in whom we failed to perform direct POC. Technical success of the interventions was achieved with 44 of 49 procedures (89.8%). No adverse events, including cholangitis, were observed.

CONCLUSIONS

A newly modified 5F balloon catheter seemed to facilitate performing intraductal balloon-guided direct POC for direct visual examination of the bile duct in patients with biliary obstruction. Continued development of endoscopes and accessories are expected to further improve the performance of direct POC.

Advanced Imaging Technology in Biliary Tract Diseases:Narrow-Band Imaging of the Bile Duct

Newly introduced direct peroral cholangioscopy and the development of video choledochoscopes have enabled more defined observation of bile duct mucosal lesions with clearer images. Narrow-band imaging (NBI) is a unique endoscopic imaging technology that provides enhanced endoscopic images of surface mucosal structures and its superficial microvessels. Advanced cholangioscopy and NBI are expected to be useful for precise evaluation and correct diagnosis of biliary tract diseases. However, the diagnostic value of advanced bile duct imaging with cholangioscopy requires further evaluation.

The Role of Endoscopy in the Diagnosis and Management of Cholangiocarcinoma

Cholangiocarcinomas (CCAs) are associated with poor overall survival, and majority of the tumors are unresectable at the time of diagnosis. Early diagnosis at a resectable stage is essential for improved outcomes. Noninvasive imaging plays an important role in evaluating patients with biliary obstruction, but is limited due to the lack of tissue sampling and in many cases due to the absence of a mass, especially for extrahepatic CCAs. Endoscopic diagnosis is needed in majority of patients with CCA and the diagnostic yield depends on the tumor location as well as the expertise and experience of the endoscopist. Endoscopic retrograde cholangiopancreatography and endoscopic ultrasound remain the most common endoscopic diagnostic tools although newer technologies including fluorescence in situ hybridization, single-operator cholangioscopy, confocal laser endomicroscopy, and intraductal ultrasound are being increasing used. Traditionally, the role of endoscopy has been mainly palliative and limited to biliary drainage in patients with obstructive jaundice, however, newer treatment options like photodynamic therapy and radiofrequency ablation have shown promise toward improved patient survival. Multidisciplinary approach that involves medical oncology, gastroenterology, radiology, and surgical oncology teams is imperative for improved outcomes. In this review, we will first review the diagnostic approach to CCAs including imaging and endoscopic methods followed by a discussion of different endoscopic techniques in management of patients after a diagnosis of CCA.

Innovations in Intraductal Endoscopy: Cholangioscopy and Pancreatoscopy

Cholangioscopy was first performed in the 1970s. We now use the term cholangiopancreatoscopy (CP) to reflect the wider application of these miniature reusable dual-operator "mother-daughter" endoscope systems and now fully disposable and digital single-operator optical catheters for evaluating the biliary or pancreatic duct. Cholangioscopy is an established modality for the management of large biliary stones and for the diagnosis and exclusion of biliary tumors. Pancreatoscopy is increasingly being performed to treat difficult pancreatic duct stones and may be used to distinguish malignant from benign ductal pathology. This review covers available CP technologies, indications, technique, efficacy, and complications.

Cholangioscopy in liver disease

Since its introduction, cholangioscopy has been used diagnostically and therapeutically. The working channel size has increased, permitting direct visualization for tissue sampling and to guide application of lithotripsy for difficult stones. Cholangioscopy utilizes endoscope and catheter-based systems. The application of slim gastroscopes for direct cholangioscopy provides better image resolution than conventional systems. Cholangioscopy has proven effective in the management of large biliary stones and for the diagnosis and exclusion of biliary tumors. Commercially available cholangioscopes are fiberoptic; those with digital video technology remain in a prototype development phase. This review covers available cholangioscope technologies, indications, technique, efficacy, and complications.

Advances in the endoscopic management of common bile duct stones

Extraction of common bile duct stones by endoscopic retrograde cholangiopancreatography generally involves biliary sphincterotomy, endoscopic papillary balloon dilation or a combination of both. Endoscopic papillary large-balloon dilation after sphincterotomy has increased the safety of large stone extraction. Cholangioscopically directed electrohydraulic and laser lithotripsy using single-operator mother-daughter systems or direct peroral cholangioscopy using ultraslim endoscopes are increasingly utilized for the management of refractory stones. In this Review, we focus on advances in endoscopic approaches and techniques, with a special emphasis on management strategies for 'difficult' common bile duct stones.

Diagnostic and therapeutic cholangiopancreatoscopy: performance of a new digital cholangioscope

BACKGROUND

High-definition cholangioscopes provide excellent images of the pancreatobiliary ductal system and may play a significant role in diagnosis and treatment of various pancreatobiliary disorders.

OBJECTIVE

To assess the performance of a new digital cholangioscope for diagnosis and treatment of pancreatobiliary disorders in clinical practice.

DESIGN

Prospective study.

SETTING

Academic hospital, tertiary-care referral center.

PATIENTS

Consecutive patients with suspected pancreatobiliary disorders.

INTERVENTION

Diagnostic or therapeutic high-definition digital cholangiopancreatoscopy.

MAIN OUTCOME MEASUREMENTS

Satisfactory visualization of the ductal mucosa and lumen and treatment of pancreatobiliary disorders when indicated.

RESULTS

A total of 28 cholangioscopy and 4 pancreatoscopy procedures were completed before breakdown of the cholangioscope. Excellent views of the ductal lumen and mucosa were obtained in all patients. In the 18 patients with indeterminate biliary strictures, high-definition cholangioscopy identified all cholangiocarcinomas but labeled as malignant only 1 of 4 strictures caused by pancreatic cancer (sensitivity 73%). All benign strictures were correctly labeled (specificity 100%). Cholangioscopy proved helpful in evaluation of various biliary disorders and lithotripsy of pancreatic stones under direct vision.

LIMITATIONS

Single center, small number of patients.

CONCLUSION

High-definition cholangioscopy is a useful adjunct to ERCP in the diagnosis and treatment of pancreatobiliary disorders. Although fragility of the cholangioscope remains a problem, the changes made in the construction of this prototype digital cholangioscope have significantly increased its durability.

Direct peroral cholangioscopy using an ultraslim upper endoscope for biliary lesions

BACKGROUND

The development of direct peroral cholangioscopy (DPOC) using an ultraslim endoscope simplifies biliary cannulation. The conventional techniques are cumbersome to perform and require advanced skills. The recent introduction of the guidewires and balloons has improved the therapeutic outcomes. Here we describe an effective and easier method for performing DPOC using an ultraslim upper endoscope.

METHODS

Indications for DPOC were the presence of stones on follow-up of patients who had previously undergone complete sphincteroplasty, including endoscopic sphincterotomy or endoscopic papillary large balloon dilatation. Fifteen patients underwent DPOC. An ultraslim endoscope was inserted perorally and was advanced into the major papilla. The ampulla of Vater was visualized by retroflexing the endoscope in the distal second portion of the duodenum, and then DPOC was performed using a wire-guided cannulation technique with an anchored intraductal balloon catheter.

RESULTS

One patient failed in the treatment due to looping of the endoscope in the fornix of the stomach. Fourteen (93.3%) were successfully treated with our modified DPOC technique. Only one patient (6.7%) experienced an adverse event (pancreatitis) who responded well to conservative management. Residual stones of the common bile duct were completely removed in 3 patients.

CONCLUSION

The modified method of DPOC is simple, safe and easy to access the bile duct.

Efficacy and safety of direct transnasal cholangioscopy with standard ultraslim endoscopes: results of a large cohort study

BACKGROUND

Direct cholangioscopy (DC) with ultraslim endoscopes and free-hand cannulation of the common bile duct (CBD) is a promising technique for evaluating and treating cholangiopathy. However, its safety and success rates are as yet unclear.

OBJECTIVE

To evaluate the overall success rates and adverse events with the procedure.

DESIGN

Single-center, prospective cohort study; 12 patients retrospectively enrolled.

SETTING

Academic tertiary referral center.

PATIENTS

A total of 100 DC procedures in 84 patients with biliary disease were evaluated prospectively.

INTERVENTIONS

DC performed with the patient under conscious sedation.

MAIN OUTCOME MEASUREMENTS

Overall success rates and adverse events with the procedure.

RESULTS

In 34 cases with small- or medium-sized sphincterotomies, sphincteroplasty was performed with a 10-mm dilating balloon before DC. The intraductal area of interest was successfully accessed in 87% of the procedures. The intended interventions were successfully carried out in 81 patients (93.1%), but failed in 6 (6.9%). In patients without significant strictures, intrahepatic exploration of the bile ducts beyond the level of the bifurcation was feasible in only 10.8%. The mean total procedure time was 38.6 ± 12.2 minutes. Adverse events occurred in 12 procedures (12%) and were managed conservatively.

LIMITATIONS

All procedures were performed by 1 endoscopist.

CONCLUSION

DC is safe and allows direct, high-resolution examination and a wide range of therapeutic options in the bile ducts in the majority of patients with biliary disease. However, the range of access is limited to the main bile duct. Suspected pathology restricted to the proximal intrahepatic ducts beyond the bifurcation is therefore not a good indication for DC.

Clinical evaluation of a prototype multi-bending peroral direct cholangioscope

BACKGROUND

Although peroral direct cholangioscopy (PDCS) is emerging as an alternative to traditional mother-daughter cholangioscopy, it is associated with high failure rates. The aim of the present study was to evaluate the ability to insert and carry out interventions using a prototype multi-bending PDCS.

PATIENTS AND METHODS

Prospective, observational clinical feasibility study was done in 41 patients with a variety of biliary diseases. A multi-bending PDCS prototype was inserted using a free-hand technique, a guidewire alone, or with a 5-Fr diameter anchoring balloon. Diagnostic and therapeutic procedures were carried out.

RESULTS

The free-hand direct insertion technique failed in all attempted cases (n = 7). Of the remaining 34 cases, successful rate of PDCS insertion into the distal bile duct was achieved by passing the PDCS over a guidewire alone (n = 6) and/or with a guidewire plus anchoring balloon (n = 28) for an overall successrate of 88.2% (30/34). In 13 (92.9%) patients without an underlying biliary stricture, PDCS insertion proximal to the bifurcation was possible. In 25 cases, biliary interventions were attempted including biopsy (n = 13), stone removal (n = 6), stent removal (n = 1), and intraductal electrohydraulic lithotripsy (n = 2) and were successful in 22 (88%). Other than two patients with procedure-related cholangitis with a mild grade of severity, no complications were observed.

CONCLUSIONS

Using a novel multi-bending prototype peroral direct cholangioscope, cholangioscopy had a high diagnostic and therapeutic success rate only when passed over a guidewire and anchoring balloon but not with the free-hand insertion technique. Comparative studies of direct cholangioscopy are warranted.

Prospective randomized comparison of short-access mother-baby cholangioscopy versus direct cholangioscopy with ultraslim gastroscopes

BACKGROUND

Mother-baby technologies, the criterion standard for cholangioscopy, have several limitations. A novel, short-access, mother-baby (SAMBA) system may improve this technique. Direct cholangioscopy (DC) was recently developed as an alternative to mother-baby cholangioscopy.

OBJECTIVE

Comparison of success rates with SAMBA and DC.

DESIGN

Single-center, randomized, controlled trial.

SETTING

Academic tertiary-care referral center.

PATIENTS

Sixty patients with suspected cholangiopathies randomized to either SAMBA (n = 30) or DC (n = 30).

INTERVENTION

Cholangioscopy under deep sedation.

MAIN OUTCOME MEASUREMENTS

Technical success rate of diagnostic or therapeutic procedure.

RESULTS

A total of 24 and 21 diagnostic procedures were performed in the SAMBA and DC groups, respectively. There were no significant differences in the overall technical success rates between SAMBA (90.0%) and DC (86.7%) (P = 1.0). There was better correlation between the endoscopic prediction and histologic findings in DC (P = .013). Procedure times were shorter in DC (P < .03). In patients without significant stenoses, SAMBA allowed intrahepatic bile duct exploration in all cases, compared with 10.5% of cases in DC (P < .01). No differences regarding adverse event rates between the groups occurred (10.0% both groups).

LIMITATIONS

Small sample size. Heterogeneous indications for cholangioscopy. DC requires advanced skills of the endoscopist. The study is not replicable.

CONCLUSION

SAMBA and DC offer high technical success rates for diagnostic and therapeutic interventions. The advantages of DC consist of superior imaging, shorter total procedure time, and a wider working channel for adequate tissue sampling. SAMBA is better than DC with regard to intraductal stability and accessibility of the intrahepatic bile ducts.

The role of direct peroral cholangioscopy using an ultraslim endoscope for biliary lesions: indications, limitations, and complications

Advantages of direct peroral cholangioscopy (POC) using an ultraslim endoscope include use of conventional endoscopy equipment, operation by a single endoscopist, and superior image quality of the biliary tree with easy application of enhanced endoscopy and a large working channel. The major diagnostic indications of this system are an evaluation of biliary strictures, filling defects, or unclear findings on cholangiogram or other imaging studies. Therapeutic application using a direct POC system can be broadened by a larger working channel. However, direct POC is difficult to apply in patients with a narrow diameter bile duct, far distal common bile duct lesion, or failed anchoring of the scope with accessories. An air embolism is a rare complication of direct POC but can be a fatal problem. Cholangitis can also occur during or after the procedure. Use of a CO₂ system instead of room air during the POC procedure and administration of antibiotics before and after the procedure are strongly recommended. Continuous development of specialized endoscopes and accessories is expected to facilitate the diagnostic and therapeutic roles of direct POC.

Novel endoscopic approaches in the diagnosis and management of biliary strictures

Indeterminate bilary strictures present the clinician with a wide differential diagnosis. Histological confirmation is usually required for treatment, but tissue acquisition remains challenging. Novel developments in endoscopic technology, such as single operator cholangioscopy and confocal endomicroscopy, have led to improvements in diagnostic accuracy in recent years. In patients with non-resectable malignant biliary obstruction, effective biliary decompression improves symptoms and enables patients to undergo palliative therapies. Improvements in endoscopic techniques, biliary stents and the development of local ablative techniques have led to further improvements in stent patency and survival in these patients. In this article, we review emerging diagnostic and therapeutic techniques for the endoscopic management of indeterminate biliary strictures.

Cholangioscopy: the biliary tree never looked so good!

PURPOSE OF REVIEW

Endoscopists have long awaited advances in the equipment and techniques for cholangiopancreatoscopy. Since the turn of the millennium, endoscopists have witnessed an explosion in the development and refinement of the capabilities of cholangioscopes as they move from being almost exclusive to tertiary care academic settings to a wider range of practices.

RECENT FINDINGS

Studies have tested and constructively critiqued the procedure, hoping to increase the success rate of diagnostic and therapeutic interventions. Many have found significant improvement upon the limitations of radiographic imaging in diagnosing diseases and achieving full clearance of biliary stones. Image quality has improved with a range of features. However, most of these still need to be studied further. The addition of balloon catheters and overtubes has improved stability and access to the biliary ducts, but comes with complications that need to be studied further.

SUMMARY

Although we still have improvements to yearn for, the future looks bright. As endoscopists continue their commitment to the promise of direct visualization of the biliary trees and the complementary tools for diagnosis and treatment, we are continuing to raise quality of care for patients with complicated biliary diseases.

Residual common bile duct stones on direct peroral cholangioscopy using ultraslim endoscope

AIM: To detect and manage residual common bile duct (CBD) stones using ultraslim endoscopic peroral cholangioscopy (POC) after a negative balloon-occluded cholangiography.

METHODS: From March 2011 to December 2011, a cohort of 22 patients with CBD stones who underwent both endoscopic retrograde cholangiography (ERC) and direct POC were prospectively enrolled in this study. Those patients who were younger than 20 years of age, pregnant, critically ill, or unable to provide informed consent for direct POC, as well as those with concomitant gallbladder stones or CBD with diameters less than 10 mm were excluded. Direct POC using an ultraslim endoscope with an overtube balloon-assisted technique was carried out immediately after a negative balloon-occluded cholangiography was obtained.

RESULTS: The ultraslim endoscope was able to be advanced to the hepatic hilum or the intrahepatic bile duct (IHD) in 8 patients (36.4%), to the extrahepatic bile duct where the hilum could be visualized in 10 patients (45.5%), and to the distal CBD where the hilum could not be visualized in 4 patients (18.2%). The procedure time of the diagnostic POC was 8.2 ± 2.9 min (range, 5-18 min). Residual CBD stones were found in 5 (22.7%) of the patients. There was one residual stone each in 3 of the patients, three in 1 patient, and more than five in 1 patient. The diameter of the residual stones ranged from 2-5 mm. In 2 of the patients, the residual stones were successfully extracted using either a retrieval balloon catheter (n = 1) or a basket catheter (n = 1) under direct endoscopic control. In the remaining 3 patients, the residual stones were removed using an irrigation and suction method under direct endoscopic visualization. There were no serious procedure-related complications, such as bleeding, pancreatitis, biliary tract infection, or perforation, in this study.

CONCLUSION: Direct POC using an ultraslim endoscope appears to be a useful tool for both detecting and treating residual CBD stones after conventional ERC.

Advanced techniques for endoscopic biliary imaging: cholangioscopy, endoscopic ultrasonography, confocal, and beyond

Cholangioscopy, endosonography, and confocal microscopy represent important technologies that expand biliary imaging beyond a level previously realized by noninvasive modalities (ultrasonography, computed tomography, and magnetic resonance cholangiopancreatography) and endoscopic retrograde cholangiopancreatography. Endoscopic ultrasonography has shown efficacy for the evaluation of indeterminate biliary strictures; however, this modality seems most reliable for distal bile duct abnormalities and in the setting of a moderate to high pretest probability for malignancy. Further refinement of these technologies, validation of their respective diagnostic criteria, and study within the context of comparative, randomized trials are needed and will contribute greatly to expedient patient care.

[Cholangioscopy]

Cholangioscopy is an important component of the management of a selected group of patients with biliary diseases. Due to the advantage of direct visualization cholangioscopy provides targeted diagnostic and therapeutic procedures under endoscopic control. Thus cholangioscopy improves the differentiation of benign and malignant intraductal lesions, targeted biopsies and precise delineation of intraductal tumor spread before surgical resection. Furthermore lithotripsy of difficult bile duct stones, ablative therapies for biliary malignancies and direct biliary drainage can be carried out under endoscopic control. Recent developments of new types of conventional peroral cholangioscopy permit feasible, safe and effective procedures that can broaden the use of this technique at reasonable costs. Hence the spectrum of diagnostic and therapeutic interventions under cholangioscopic control will be further expanded in the future.

Usefulness of percutaneous transhepatic cholangioscopic lithotomy for removal of difficult common bile duct stones

Background/Aims

Approximately 5% to 10% of common bile duct (CBD) stones are difficult to remove by conventional endoscopic methods. Percutaneous transhepatic cholangioscopic lithotomy (PTCSL) can be an alternative method for this condition, but is not well established yet. The aim of this study was to evaluate the clinical efficacy and safety of PTCSL for removal of difficult CBD stones.

Methods

This study is a retrospective review of 34 consecutive patients who underwent unsuccessful removal of CBD stones using conventional endoscopic methods between December 2008 and July 2010 and were subsequently treated using PTCSL.

Results

Among 443 patients with CBD stones, 34 patients (7.8%) failed to achieve stone removal using conventional endoscopic methods. Of these 34 patients, 33 were treated using PTCSL. In all 33 cases (100%), complete stone removal was achieved using PTCSL. Most complications (15/17, 88.2%) were mild and transient. Major complications occurred in two patients (6.1%) who experienced hemobilia, and percutaneous transhepatic biliary drainage tract disruption, respectively; which were fully recovered without mortality.

Conclusions

Despite prolonged hospital stay and temporary decline of quality of life, PTCSL is an effective and safe method in the management of difficult CBD stones, especially in patients with difficulty in approaching the affected bile duct.

Endoscopic management of difficult common bile duct stones

Endoscopy is widely accepted as the first treatment option in the management of bile duct stones. In this review we focus on the alternative endoscopic modalities for the management of difficult common bile duct stones. Most biliary stones can be removed with an extraction balloon, extraction basket or mechanical lithotripsy after endoscopic sphincterotomy. Endoscopic papillary balloon dilation with or without endoscopic sphincterotomy or mechanical lithotripsy has been shown to be effective for management of difficult to remove bile duct stones in selected patients. Ductal clearance can be safely achieved with peroral cholangioscopy guided laser or electrohydraulic lithotripsy in most cases where other endoscopic treatment modalities have failed. Biliary stenting may be an alternative treatment option for frail and elderly patients or those with serious co morbidities.

Diagnostic and therapeutic direct peroral cholangioscopy using an intraductal anchoring balloon

AIM: To report our experience using a recently introduced anchoring balloon for diagnostic and therapeutic direct peroral cholangioscopy (DPOC).

METHODS: Consecutive patients referred for diagnostic or therapeutic peroral cholangioscopy were evaluated in a prospective cohort study. The patients underwent DPOC using an intraductal anchoring balloon, which was recently introduced to allow consistent access to the biliary tree with an ultraslim upper endoscope. The device was later voluntarily withdrawn from the market by the manufacturer.

RESULTS: Fourteen patients underwent DPOC using the anchoring balloon. Biliary access with an ultraslim upper endoscope was accomplished in all 14 patients. In 12 (86%) patients, ductal access required sphincteroplasty with a 10-mm dilating balloon. Intraductal placement of the ultraslim upper endoscope allowed satisfactory visualization of the biliary mucosa to the level of the confluence of the right and left hepatic ducts in 13 of 14 patients (93%). Therapeutic interventions by DPOC were successfully completed in all five attempted cases (intraductal biopsy in one and DPOC guided laser lithotripsy in four). Adverse events occurred in a patient on immunosuppressive therapy who developed an intrahepatic biloma at the site of the anchoring balloon. This required hospitalization and antibiotics. Repeat endoscopic retrograde cholangiopancreatography 8 wk after the index procedure showed resolution of the biloma.

CONCLUSION: Use of this anchoring balloon allowed consistent access to the biliary tree for performance of diagnostic and therapeutic DPOC distal to the biliary bifurcation.

Evaluating the feasibility of direct peroral cholangioscopy training with an endoscopic simulator

INTRODUCTION

Direct peroral cholangioscopy (DPOCS) was reported to present clinical potential, and creating a target-specific training program for biliary endoscopists who lack experience with DPOCS is an important task.

METHODS

This prospective and observational study used five male domestic pigs. Optimal procedures were decided after pilot tests using an in vivo live porcine model. A total of three ERCP men were enrolled into the training program. The objective parameters, including the rate of success and complications, and the length of the procedure, were recorded for each participant.

RESULTS

In the training program, all the trainees successfully performed DPOCS and biopsies without significant complications. Close observation, free discussions, and the sharing of experiences helped shorten the total procedure time from 37.3 to 18.5 min.

CONCLUSIONS

This training program is a feasible approach to help biliary endoscopists acquire the experience for DPOCS with the ultrathin endoscope.