Diagnostic accuracy and interobserver agreement of digital single-operator cholangioscopy for indeterminate biliary strictures

Multimodal convolutional neural network-based algorithm for real-time detection and differentiation of malignant and inflammatory biliary strictures in cholangioscopy: a proof-of-concept study (with video)

BACKGROUND AND AIMS

Deep learning algorithms gained attention for detection (computer-aided detection [CADe]) of biliary tract cancer in digital single-operator cholangioscopy (dSOC). We developed a multimodal convolutional neural network (CNN) for detection (CADe), characterization and discriminating (computer-aided diagnosis [CADx]) between malignant, inflammatory, and normal biliary tissue in raw dSOC videos. In addition, clinical metadata were included in the CNN algorithm to overcome limitations of image-only models.

METHODS

Based on dSOC videos and images of 111 patients (total of 15,158 still frames), a real-time CNN-based algorithm for CADe and CADx was developed and validated. We established an image-only model and metadata injection approach. In addition, frame-wise and case-based predictions on complete dSOC video sequences were validated. Model embeddings were visualized, and class activation maps highlighted relevant image regions.

RESULTS

The concatenation-based CADx approach achieved a per-frame area under the receiver-operating characteristic curve of .871, sensitivity of .809 (95% CI, .784-.832), specificity of .773 (95% CI, .761-.785), positive predictive value of .450 (95% CI, .423-.467), and negative predictive value of .946 (95% CI, .940-.954) with respect to malignancy on 5715 test frames from complete videos of 20 patients. For case-based diagnosis using average prediction scores, 6 of 8 malignant cases and all 12 benign cases were identified correctly.

CONCLUSIONS

Our algorithm distinguishes malignant and inflammatory bile duct lesions in dSOC videos, indicating the potential of CNN-based diagnostic support systems for both CADe and CADx. The integration of non-image data can improve CNN-based support systems, targeting current challenges in the assessment of biliary strictures.

Endoscopic evaluation of indeterminate biliary strictures: Cholangioscopy, endoscopic ultrasound, or both?

Accurate and timely diagnosis of biliary strictures can be challenging. Because the diagnostic sensitivity and accuracy of standard endoscopic retrograde cholangiopancreatography-based tissue sampling for malignancy are suboptimal, additional endoscopic evaluation by cholangioscopy and/or endoscopic ultrasound (EUS) is often necessary to differentiate between malignant and benign biliary strictures to guide clinical management. While direct visualization by cholangioscopy and/or high-resolution imaging by EUS are often the first step in the evaluation of an indeterminate biliary stricture (IDBS), tissue diagnosis by cholangioscopy-guided biopsy and/or EUS-guided fine-needle tissue acquisition is the preferred modality to establish a diagnosis of malignancy. Because each modality has its own strengths and limitations, selection of cholangioscopy and EUS is best guided by the biliary stricture location and local expertise. Artificial intelligence-assisted diagnosis, biopsy forceps with improved design, contrast-enhanced EUS, and dedicated fine-needle biopsy devices are recent technological advances that may further improve the diagnostic performance of cholangioscopy and EUS in patients with IDBS.

Role of endoscopy in hepatology

The growing and evolving field of EUS and advanced hepatobiliary endoscopy has amplified traditional upper gastrointestinal endoscopy and unveiled novel options for remaining unsolved hepatobiliary issues, both diagnostically and therapeutically. This conceptually appealing and fascinating integration of endoscopy within the practice of hepatology is referred to as 'endo-hepatology'. Endo-hepatology focuses on the one hand on disorders of the liver parenchyma and liver vasculature and of the hepatobiliary tract on the other hand. Applications hanging under the umbrella of endohepatology involve amongst others EUS-guided liver biopsy, EUS-guided portal pressure measurement, EUS-guided portal venous blood sampling, EUS-guided coil & glue embolization of gastric varices and spontaneous portosystemic shunts as well as ERCP in the challenging context of (decompensated cirrhosis) and intraductal cholangioscopy for primary sclerosing cholangitis. Although endoscopic proficiency however does not necessarily equal in an actual straightforward end-solution for currently persisting (complex) hepatobiliary situations. Therefore, endohepatology continues to generate high-quality data to validate and standardize procedures against currently considered (best available) "golden standards" while continuing to search and trying to provide novel minimally invasive solutions for persisting hepatological stalemate situations. In the current review, we aim to critically appraise the status and potential future directions of endo-hepatology.

Diagnostic accuracy and interobserver agreement of cholangioscopy for indeterminate biliary strictures: A single-center experience

BACKGROUND AND STUDY AIMS

Characterization of indeterminate biliary strictures (IDBS) still represents a major challenge. Digital single-operator cholangioscopy (DSOC) could potentially overcome limits of conventional biopsy and brush sampling. The aim of this study was to compare diagnostic accuracy of visual evaluation and DSOC-guided biopsies to conventional trans-papillary sampling techniques and to evaluate the inter-observer agreement (IOA) on visual diagnosis.

PATIENTS AND METHODS

All consecutive patients undergoing DSOC-guided biopsy after conventional sampling techniques for IDBS during a six-year period were retrospectively evaluated. Final diagnosis was based on histological evaluation of the surgical specimen if available or a clinical follow-up of at least 6 months. For IOA, 20-second DSOC clips were retrospectively reviewed by 6 experts and 6 trainees and classified according to the Monaco Classification.

RESULTS

Thirty-five patients underwent DSOC for IDBS in the study period; 14 patients (F = 9) with a median age of 64 years (range 53-76) met the study aim. After DSOC, strictures location was changed in three patients (additional yield of 21.4 %). Intraductal DSOC-guided biopsy were technically successful in all cases, with an adequacy of 92.8 %. No adverse events were recorded. Final diagnosis was benign disease in five cases and cholangiocarcinoma in the others. For IOA, 29 videos were evaluated with almost perfect agreement for final diagnosis (kappa 0.871; agreement 93.1, p <0.001), although overall accuracy of DSOC visual finding was 73.6 % and 64.4 % for experts and trainees, respectively.

CONCLUSIONS

DSOC could improve diagnostic accuracy for IDBS, since it showed high sensitivity for visual finding and high specificity for DSOC guided-biopsy. Visual diagnosis seems reliable for diagnosis using the Monaco Classification.

Case report: The diagnostic dilemma of indeterminate biliary strictures: report on two cases with a literature review

Background

It is still a challenging problem for clinicians to explore the nature of the indeterminate biliary strictures (IBSs). Approximately 20% of biliary strictures remain undetermined after a thorough preoperative assessment.

Case presentation

Here, we present two cases of indeterminate biliary strictures patients, whose cross- sectional imaging and endoscopic examination were nondiagnostic. The patients underwent exploratory laparotomy finally and were confirmed as malignancy. We also reviewed the recent reports in literatures regarding the evaluation of IBSs.

Conclusions

Given the majority of the biliary strictures are malignancy, preoperative differentiation between benign and malignant is critical for choosing the best therapeutic regimen. Thus, close follow-up, multiple multidisciplinary discussion, and prompt surgical exploration are necessary for some difficult diagnostic cases.

Endoscopic procedures in hepatology: Current trends and new developments

Gastrointestinal endoscopy has long been a reliable backbone in the diagnosis and management of hepatobilary disorders and their complications. However, with evolving non-invasive testing, personalised medicine has reframed the utility and necessity of endoscopic screening. Conversely, the growing interest and use of endoscopic ultrasound (EUS) and advanced endoscopy within gastrointestinal units has also opened novel diagnostic and therapeutic avenues for patients with various hepatobiliary diseases. The integration of "advanced endoscopy" within the practice of hepatology is nowadays referred to as "endo-hepatology". In essence, endo-hepatology consists of two pillars: one focusing primarily on disorders of the liver parenchyma, vascular disorders, and portal hypertension, which is mainly captured via EUS, while the other targets the hepatobiliary tract via endoscopic retrograde cholangiopancreatography and advanced imaging. Applications under the umbrella of endo-hepatology include, amongst others, EUS-guided liver biopsy, EUS-guided portal pressure gradient measurement, coil and glue embolisation of gastric varices as well as cholangioscopy. As such endo-hepatology could become an attractive concept wherein advanced endoscopy might reinforce the medical management of patients with hepatobiliary disorders and their complications after initial basic work-up. In this review, we discuss current trends and future developments within endo-hepatology and the remaining hurdles to overcome.

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.

Improved fluoroscopy-guided biopsies in the diagnosis of indeterminate biliary strictures: a multi-center retrospective study

To evaluate the diagnostic accuracy of improved fluoroscopy-guided biopsies for indeterminate biliary strictures (IBDS). A multi-center retrospective study was performed. Patients with IBDS who underwent digital single-operator cholangioscopy (DSOC) and improved fluoroscopy-guided biopsies procedures were included. The individual sensitivity, specificity, and accuracy were analyzed. A total of 67 patients were enrolled in this multi-center retrospective study. The DSOC and improved fluoroscopy-guided biopsies procedures were successfully performed in all cases (100%). The sensitivity, specificity, and accuracy values were 83.3%, 89.5%, and 85.1% for DSOC visual impression; 95.8%, 94.7%, and 95.5% for improved fluoroscopy-guided biopsies procedures, respectively. The sensitivity and accuracy of improved fluoroscopy-guided biopsies were significantly higher compared with DSOC visual impression. Four patients (6.0%, 4/67) occurred adverse events after the procedures. Improved fluoroscopy-guided biopsies had a high diagnostic accuracy of IBDS diagnosis.

A novel peroral digital cholangioscope with a large accessory channel: An experimental study

BACKGROUND/PURPOSE

A peroral cholangioscope (POCS) can allow direct visualization of the biliary mucosa and its use is becoming more widespread due to improvements in functionality, image quality, and operability, as well as the development of related devices. Recently, a novel mother-baby peroral cholangioscope (nMB-POCS) with a large (2-mm) accessory channel has been developed. In this study, we evaluated the feasibility of this novel POCS in a dry simulation and animal model.

METHODS

We evaluated the ease of insertion and maneuverability of the nMB-POCS, the image quality, and the passage of the devices into the accessory channel and into the common bile duct in a dry and live porcine model.

RESULTS

In both models, the nMB-POCS could be easily inserted into the duodenoscope and into the distal bile duct and hilum. The image quality was good, and it was possible to observe the surface structure and the vascular network of the bile duct mucosa in detail.

CONCLUSIONS

The nMB-POCS with its larger accessory channel is expected to improve the efficiency of diagnosis and  treatment, and reduce the procedure time. Clinical studies in patients are warranted.

Cholangioscopy for biliary diseases

PURPOSE OF REVIEW

Cholangioscopy is a mini-invasive endoscopic procedure, which consists in a direct intraductal visualization of the biliary tract. The purpose of this review is to summarize the technique, the clinical applications, as well as future perspectives of cholangioscopy.

RECENT FINDINGS

Numerous technologic advances during the last decades have allowed for an improved utility and functionality, leading to a broader use of this procedure, for diagnostic or therapeutic purposes, in the setting of biliary diseases. Novel tools and emerging indications have been developed and more are yet to come.

SUMMARY

Cholangioscopy can be performed by peroral, percutaneous transhepatic or intra-operative transcystic or transcholedochal access. Clinical applications of cholangioscopy are multiple, ranging from visual impression and optical guided biopsies of indeterminate biliary strictures to the management of difficult stones , guidance before biliary stenting and retrieval of migrated ductal stents. Multiple devices such as lithotripsy probes, biopsy forceps, snares and baskets have been developed to help achieve these procedures successfully.Cholangioscopy has improved the way biliary diseases can be visualized and treated. New technology, accessories, and applications are expected in the future.

Identification of patients with malignant biliary strictures using a cholangioscopy-based deep learning artificial intelligence (with video)

BACKGROUND AND AIMS

Accurately diagnosing malignant biliary strictures (MBSs) as benign or malignant remains challenging. It has been suggested that direct visualization and interpretation of cholangioscopy images provide greater accuracy for stricture classification than current sampling techniques (ie, brush cytology and forceps biopsy sampling) using ERCP. We aimed to develop a convolutional neural network (CNN) model capable of accurate stricture classification and real-time evaluation based solely on cholangioscopy image analysis.

METHODS

Consecutive patients with cholangioscopy examinations from 2012 to 2021 were reviewed. A CNN was developed and tested using cholangioscopy images with direct expert annotations. The CNN was then applied to a multicenter, reserved test set of cholangioscopy videos. CNN performance was then directly compared with that of ERCP sampling techniques. Occlusion block heatmap analyses were used to evaluate and rank cholangioscopy features associated with MBSs.

RESULTS

One hundred fifty-four patients with available cholangioscopy examinations were included in the study. The final image database comprised 2,388,439 still images. The CNN demonstrated good performance when tasked with mimicking expert annotations of high-quality malignant images (area under the receiver-operating characteristic curve, .941). Overall accuracy of CNN-based video analysis (.906) was significantly greater than that of brush cytology (.625, P = .04) or forceps biopsy sampling (.609, P = .03). Occlusion block heatmap analysis demonstrated that the most frequent image feature for an MBS was the presence of frond-like mucosa/papillary projections.

CONCLUSIONS

This study demonstrates that a CNN developed using cholangioscopy data alone has greater accuracy for biliary stricture classification than traditional ERCP-based sampling techniques.

Current endoscopic approaches to biliary strictures

PURPOSE OF REVIEW

To summarize the current status and future perspectives of the endoscopic management of biliary strictures.

RECENT FINDINGS

In addition to conventional diagnostic modalities, such as cross-sectional imaging and endoscopic ultrasonography (EUS), per-oral cholangioscopy is helpful for indeterminate biliary strictures. It allows direct visualization of the biliary tract and targeted biopsy. For distal malignant biliary obstruction (MBO), a self-expandable metal stent (SEMS) via endoscopic retrograde cholangiopancreatography (ERCP) is a standard of care. EUS-guided biliary drainage (EUS-BD) is an emerging alternative to percutaneous transhepatic biliary drainage in cases with failed ERCP. EUS-BD is also an effective salvage option for perihilar MBO, which can not be managed via ERCP or percutaneous transhepatic biliary drainage. Preoperative drainage is necessary for most jaundiced patients as neoadjuvant chemotherapy is widely administered for resectable and borderline resectable pancreatic cancer, and a SEMS is preferred in this setting, too. For benign biliary strictures, a covered SEMS can improve stricture resolution and reduce the number of endoscopic sessions as compared to plastic stents.

SUMMARY

ERCP and EUS play a central role in the diagnosis and drainage for both malignant and benign biliary strictures.

Future of Cholangioscopy

This article highlights the current status of cholangioscopy. In addition, the authors present their view on the future directions of cholangioscopy, including novel clinical applications, the need for technologic developments, and the expansion on the use of cholangioscopy in clinical practice. The authors envision that cholangioscopy will eventually become a conventional tool in the shelf of any biliary endoscopist. Future technologic improvements including optics, maneuverability, and full device accessories, plus the introduction of real-time artificial intelligence algorithms, will optimize the outcomes of cholangioscopy, but baseline proficiency in therapeutic endoscopic retrograde cholangiopancreatography will remain necessary for its successful utilization.

Multidisciplinary Approach to Indeterminate Biliary Strictures

Biliary strictures that remain unclassified after cross-sectional imaging and endoscopic retrograde cholangiopancreatography-based tissue sampling are defined as indeterminate biliary strictures (IDBS). A substantial proportion of biliary strictures fall into this category due to low sensitivity of brush cytology and intraductal biopsy. Over last few decades, several modalities have emerged for the evaluation of IDBS. Of these, cholangioscopy and endosonography are the frontrunners and have cemented their place for the evaluation of IDBS. Both of these modalities are widely available, and therefore, biliary strictures that remain uncharacterized after their utilization represent IDBS in the current era.

The Role of Cholangioscopy and EUS in the Evaluation of Indeterminate Biliary Strictures

Bile duct stenosis continues to present a diagnostic dilemma for clinicians. It is important to establish the benign or malignant nature of the stricture early in order to avoid any unnecessary delay in medical treatment or surgery. Tissue acquisition for histological diagnosis is particularly crucial when the initial diagnostic work up is inconclusive. The diagnostic yield from the conventional endoscopic retrograde cholangiopancreatography (ERCP) with brushing and biopsy is suboptimal. Patients with indeterminate biliary strictures (IDBSs) often require a multi-disciplinary diagnostic approach and additional endoscopic evaluation, including cholangioscopy and endoscopic ultrasound, before a final diagnosis can be reached. In this article, we discuss the recent endoscopic advancements in the diagnosis of biliary stricture with a focus on the roles of cholangioscopy and endoscopic ultrasound (EUS).

Artificial intelligence in the endoscopic approach of biliary tract diseases: A current review

In recent years there have been major developments in the field of artificial intelligence. The different areas of medicine have taken advantage of this tool to make various diagnostic and therapeutic methods more effective, safe, and user-friendly. In this way, artificial intelligence has been an increasingly present reality in medicine. In the field of Gastroenterology, the main application has been in the detection and characterization of colonic polyps, but an increasing number of studies have been published on the application of deep learning systems in other pathologies of the gastrointestinal tract. Evidence of the application of artificial intelligence in the assessment of biliary tract is still scarce. Some studies support the usefulness of these systems in the investigation and treatment of choledocholithiasis, demonstrating that they have the potential to be integrated into clinical practice and endoscopic procedures, such as endoscopic retrograde cholangiopancreatography. Its application in cholangioscopy for the investigation of undetermined biliary strictures also seems to be promising. Assessing the bile duct through endoscopic ultrasound can be challenging, especially for less experienced operators, thus becoming an area of potential interest for artificial intelligence. In this review, we summarize the state of the art of artificial intelligence in the endoscopic diagnosis and treatment of biliary diseases.