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.
Key points
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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 (ERCP).
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For the delineation of indeterminate bile duct strictures, cholangioscopy and confocal microscopy have shown a complimentary role to ERCP.
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Endoscopic ultrasonography (EUS) 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.
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One advantage of EUS in this context is that it is a safe modality with a more favorable profile for risks of complications when compared with imaging techniques that rely on transpapillary access.
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Overall, major barriers for these techniques are linked to the need for substantial specialized training; with much of their efficacy in terms of image interpretation relying on the subjective gestalt of an experienced endoscopist.
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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.
Imaging the biliary tree: diagnostic challenges and dilemmas
Multiple modalities are in clinical use for noninvasive imaging of the biliary tree. Abdominal ultrasonography, computed tomography (CT), and magnetic resonance cholangiopancreatography (MRCP) are low-risk, widely available imaging modalities, which have been extensively studied for biliary disease. These modalities reliably identify ductal dilatation and, most notably with MRCP, can be excellent for the purpose of diagnosing clinically significant stone disease. However, evaluation of the biliary mucosal abnormalities can be challenging with noninvasive modalities. Also, rates of false-negative results for stone disease increase substantially by location and stone size (≤3 mm) with noninvasive imaging modalities.
For 40 years, endoscopic retrograde cholangiopancreatography (ERCP) has been a well-established tool for both diagnosis and therapy for biliary ductal disease. However, in the setting of advances in noninvasive imaging the role of diagnostic ERCP is diminishing. ERCP is now being changed to a predominantly therapeutic intervention. One notable exception to this trend is the continued use of diagnostic ERCP for the provision of index pathology. Yet as a stand-alone modality to establish a tissue diagnosis, ERCP remains hindered by poor sensitivity; reported between 54% and 71% even with combined brush cytology and intraductal biopsies. Various adjunct techniques have been explored to improve the sensitivity of brush cytology obtained by ERCP, including fluorescence in situ hybridization (FISH) and immunohistochemical staining of specimens. FISH has been reported to improve sensitivity 10% to 20% when cytology is negative for malignancy; however, results are overall modest. Other techniques, such as DNA methylation of tissue samples and p53 immunostaining of brushed specimens, have yet to show consistent benefit for routine practice despite initial promise. Longer brushes with stiff bristles have failed to show a significant improvement in sensitivity and hence cancer detection rate. Cytologic sampling both before and after endoscopic dilation of the bile duct showed a sensitivity around 30%, despite an improved diagnostic yield with repeat brushings. Also, ERCP is not without risk of complications, principal of which is post-ERCP pancreatitis. Hence, repetitive ERCP procedures are less than ideal.
Within the spectrum of biliary disease, one of the most challenging diagnostic dilemmas is the indeterminate stricture. The differential diagnosis for an undiagnosed biliary stricture encompasses both benign (primary sclerosing cholangitis [PSC], IgG4-related cholangitis, autoimmune pancreatitis) and malignant disease (cholangiocarcinoma, hepatocellular carcinoma, and metastatic disease). Cholangiocarcinoma is especially challenging to diagnose in this context. Frequently presenting as a biliary stricture, it may be found with or without a mass and its most common risk factor in Western countries is PSC, a benign fibroinflammatory disease that can independently cause benign biliary strictures. Hilar lesions pose an additional diagnostic challenge. Hilar cholangiocarcinoma often has a relatively indolent course. Also, as many as 24% of patients with hilar strictures suspicious for cholangiocarcinoma based on abnormal tumor markers and imaging may have benign disease. However, cholangiocarcinoma is the second most common primary hepatic malignancy, and emphasis is placed on early detection (before lymphatic involvement or extraluminal invasion), because patients may enjoy a favorable 5-year survival.
In addition, biliary stone disease can be a diagnostic challenge. It is estimated that more than 20 million people in the United States have gallstone disease, leading to more than $6.2 billion dollars in annual costs. Choledocholithiasis occurs in approximately 15% to 20% of patients with symptomatic cholelithiasis. The potential for morbidity is high when untreated, with consequent complications of cholangitis, hepatic abscess, and acute pancreatitis. American Society for Gastrointestinal Endoscopy guidelines suggest that patients at intermediate risk of choledocholithiasis may benefit from additional biliary imaging before or during cholecystectomy. As mentioned earlier, noninvasive imaging has the potential for false-negative evaluations within this context. ERCP also has diagnostic limitations. Small stones can be lost in the background of an undiluted contrast cholangiogram, and large stones can block ducts, preventing flow of contrast. A multicenter study presented in abstract form reported that almost 30% of patients who underwent ERCP for indications other than suspected choledocholithiasis had a false-negative cholangiogram for stone disease when followed and confirmed by cholangioscopy. Residual stone burden after mechanical lithotripsy was also found to be common in a similarly designed study.
Overall, biliary imaging for the diagnosis of both benign and malignant disease remains a challenge for reliability and consistency. Consequently, a great deal of attention and research have been dedicated toward advanced modalities of biliary imaging, which are outlined in this article.
Imaging the biliary tree: diagnostic challenges and dilemmas
Multiple modalities are in clinical use for noninvasive imaging of the biliary tree. Abdominal ultrasonography, computed tomography (CT), and magnetic resonance cholangiopancreatography (MRCP) are low-risk, widely available imaging modalities, which have been extensively studied for biliary disease. These modalities reliably identify ductal dilatation and, most notably with MRCP, can be excellent for the purpose of diagnosing clinically significant stone disease. However, evaluation of the biliary mucosal abnormalities can be challenging with noninvasive modalities. Also, rates of false-negative results for stone disease increase substantially by location and stone size (≤3 mm) with noninvasive imaging modalities.
For 40 years, endoscopic retrograde cholangiopancreatography (ERCP) has been a well-established tool for both diagnosis and therapy for biliary ductal disease. However, in the setting of advances in noninvasive imaging the role of diagnostic ERCP is diminishing. ERCP is now being changed to a predominantly therapeutic intervention. One notable exception to this trend is the continued use of diagnostic ERCP for the provision of index pathology. Yet as a stand-alone modality to establish a tissue diagnosis, ERCP remains hindered by poor sensitivity; reported between 54% and 71% even with combined brush cytology and intraductal biopsies. Various adjunct techniques have been explored to improve the sensitivity of brush cytology obtained by ERCP, including fluorescence in situ hybridization (FISH) and immunohistochemical staining of specimens. FISH has been reported to improve sensitivity 10% to 20% when cytology is negative for malignancy; however, results are overall modest. Other techniques, such as DNA methylation of tissue samples and p53 immunostaining of brushed specimens, have yet to show consistent benefit for routine practice despite initial promise. Longer brushes with stiff bristles have failed to show a significant improvement in sensitivity and hence cancer detection rate. Cytologic sampling both before and after endoscopic dilation of the bile duct showed a sensitivity around 30%, despite an improved diagnostic yield with repeat brushings. Also, ERCP is not without risk of complications, principal of which is post-ERCP pancreatitis. Hence, repetitive ERCP procedures are less than ideal.
Within the spectrum of biliary disease, one of the most challenging diagnostic dilemmas is the indeterminate stricture. The differential diagnosis for an undiagnosed biliary stricture encompasses both benign (primary sclerosing cholangitis [PSC], IgG4-related cholangitis, autoimmune pancreatitis) and malignant disease (cholangiocarcinoma, hepatocellular carcinoma, and metastatic disease). Cholangiocarcinoma is especially challenging to diagnose in this context. Frequently presenting as a biliary stricture, it may be found with or without a mass and its most common risk factor in Western countries is PSC, a benign fibroinflammatory disease that can independently cause benign biliary strictures. Hilar lesions pose an additional diagnostic challenge. Hilar cholangiocarcinoma often has a relatively indolent course. Also, as many as 24% of patients with hilar strictures suspicious for cholangiocarcinoma based on abnormal tumor markers and imaging may have benign disease. However, cholangiocarcinoma is the second most common primary hepatic malignancy, and emphasis is placed on early detection (before lymphatic involvement or extraluminal invasion), because patients may enjoy a favorable 5-year survival.
In addition, biliary stone disease can be a diagnostic challenge. It is estimated that more than 20 million people in the United States have gallstone disease, leading to more than $6.2 billion dollars in annual costs. Choledocholithiasis occurs in approximately 15% to 20% of patients with symptomatic cholelithiasis. The potential for morbidity is high when untreated, with consequent complications of cholangitis, hepatic abscess, and acute pancreatitis. American Society for Gastrointestinal Endoscopy guidelines suggest that patients at intermediate risk of choledocholithiasis may benefit from additional biliary imaging before or during cholecystectomy. As mentioned earlier, noninvasive imaging has the potential for false-negative evaluations within this context. ERCP also has diagnostic limitations. Small stones can be lost in the background of an undiluted contrast cholangiogram, and large stones can block ducts, preventing flow of contrast. A multicenter study presented in abstract form reported that almost 30% of patients who underwent ERCP for indications other than suspected choledocholithiasis had a false-negative cholangiogram for stone disease when followed and confirmed by cholangioscopy. Residual stone burden after mechanical lithotripsy was also found to be common in a similarly designed study.
Overall, biliary imaging for the diagnosis of both benign and malignant disease remains a challenge for reliability and consistency. Consequently, a great deal of attention and research have been dedicated toward advanced modalities of biliary imaging, which are outlined in this article.
Cholangioscopy
Cholangioscopy is a technique for direct endoscopic visualization of the bile ducts. Within this context, its use has been reported from expert centers, both for targeted tissue sampling and intraductal interventions. Common bile duct endoscopy was first reported in the form of intraoperative choledochoscopy. This technique was reported as early as 1941, used as a measure to exclude choledocholithiasis after cholecystectomy. Twenty years later, this technology matured into a dedicated flexible choledochoscope, introduced via a percutaneous, transhepatic approach to diagnose biliary disease. Transhepatic approaches are still in use; however, these are reserved for patients who cannot undergo a peroral intervention, such as in cases of altered anatomy or after peroral endoscopic failure. Peroral cholangioscopy was first reported in 1976 and is now the most common form of direct biliary endoscopy. Early techniques described the passage of a thin cholangioscope into the common bile duct (CBD) through the accessory port of a duodenoscope. A single-scope direct peroral approach was described 1 year later; performed with an 8.8-mm fiberscope inserted into the biliary system after endoscopic papillotomy.
Cholangioscopy has now evolved into a variety of systems used for multiple indications. However, its use continues to be largely realized at academic institutions and tertiary referral centers. Mother-baby cholangioscopy is a technique whereby a smaller, thinner cholangioscope (baby) is passed through the instrument channel of a larger duodenoscope (mother). Originally requiring 2 skilled endoscopists to manipulate a dual-endoscope system, early models were also limited by an absence of irrigation channel, fragile, small-caliber equipment, lack of tip deflection, and suboptimal image quality. SpyGlass Direct Visualization System (Boston Scientific, Natick, MA) is a late, single-operator system that attempted to address these early limitations ( Fig. 1 ). Introduced in 2006, SpyGlass is a single-operator system, yet it is based on the original mother-baby platform. An independent instrument, with an operator interface that allows 4-way tip defection, it attaches near the instrument channel of a duodenoscope. Using a flexible, 230-cm, 10-French access catheter, it is delivered into the biliary tract after papillary sphincterotomy or dilation, through the instrument channel of a duodenoscope or colonoscope (minimum channel diameter of 3.4 mm). The potential of the catheter for 4-way tip defection and its 3 ports (irrigation channel, a port for insertion of an optical probe able to provide 6000-pixel images, and a 1.2-mm accessory channel) represent advancement over early cholangioscopic systems.
Direct peroral video cholangioscopy is a recent system, which entails the insertion of an ultraslim endoscope into the biliary tree to achieve high-quality digital imaging. These endoscopes range from 5 to 6 mm in external diameter and can be fed over a stiff 0.89-mm (0.035-in) Jagwire (Boston Scientific, Natick, MA) to gain access to the bile duct. Once the duodenoscope has been removed and fluoroscopic-guided wire exchange has been performed, the ultraslim endoscope is backloaded over the guidewire and advanced into the biliary system. A balloon-assisted anchoring system has also been reported to maintain stable access. Direct peroral choledochoscopes use video imaging, which despite formal comparative studies seems to be superior to many mother-baby systems. In addition to being single-user system and providing high-quality images, models also provide a larger, 2-mm working channel for therapeutic interventions.
The safety profile of peroral cholangioscopy is still being defined. Overall, current data suggest a similar complication rate to that of ERCP alone, with some notable caveats. Chen and colleagues report an incidence of serious adverse effects in 7.5% cases of diagnostic single-operator cholangioscopy and in 6.1% of patients undergoing directed stone fragmentation. A retrospective review of 402 patients who underwent cholangiopancreatoscopy reported significantly higher rates of postcholangioscopy cholangitis (1.0%) when compared with 3475 patients who underwent ERCP alone (0.2%). There were no reported significant differences in the rates of pancreatitis or perforation. The investigators suggest that increased rates of cholangitis may be related to intraprocedural saline irrigation. Of additional concern is that cholangioscopy may more frequently induce episodes of cholangitis in patients with PSC or complex strictures. For these reasons, prophylactic antibiotics with or without postprocedural biliary drainage are strongly recommended. Direct peroral video cholangioscopy has several reports of episodes of air embolism.
Peroral cholangioscopy is now considered for a variety of diagnostic and therapeutic indications. This article focuses on (1) the evaluation of indeterminate bile duct strictures, (2) targeted tissue sampling to assist with the diagnosis or exclusion of malignancy, and (3) management of biliary stone disease.
Evaluation of Indeterminate and Malignant Biliary Strictures
As outlined earlier, efforts to improve the yield of diagnostic index pathology obtained during cholangiography has realized limited success. False-negative results remain unacceptably high, complicating and delaying timely patient care, especially in those with malignancy. Multiple studies have explored cholangioscopic systems to improve diagnostic accuracy in the evaluation of indeterminate strictures.
Current data suggest that cholangioscopy with and without biopsy is associated with an improved diagnostic yield when compared with ERCP alone. The SpyGlass system allows for direct visualization of biliary epithelium, targeting tissue sampling of previously undefined biliary lesions. Studies have reported adequate tissue sampling using the SpyBite biopsy forceps in 82% to 97% of cases.
Single-operator cholangioscopy with biopsy has shown a possible, incremental accuracy as high as 85% for characterizing indeterminate strictures, when compared with cytology and transpapillary biopsy (34% and 54%, respectively). Sensitivity has been reported to be as high as 90% for this technique in diagnosing malignancy, with little impact on specificity and accuracy.
Benefits of overall ERCP-cholangiography–directed index pathology have been reported to be related to: (1) direct visualization of epithelial features, some of which are now considered specific for malignancy, and (2) targeting biopsies for more meaningful specimens for histopathologic review. Unique to cholangioscopy is the added diagnostic usefulness of identifying various mucosal abnormalities suggestive of malignancy by an experienced biliary endoscopist. Mucosal neovascularization, manifested by irregular vasculature and dilated blood vessels, is reported as the most specific finding for malignancy (see Fig. 1 ). In 1 study, detection of this abnormality endoscopically was reported to carry a sensitivity of nearly 100% Nodularity and irregular patterns of luminal stenosis have also been appreciated within the context of malignant disease; however, these are believed to be lesser features with lower specificity (see Fig. 1 ). The significance of these findings within the context of malignancy and their association with benign disease is a major concern, and new modalities (ie, methylene blue-aided inspection) are being explored to further evaluate and validate these endoscopic characteristics.
The diagnostic usefulness of both inspection in addition directed biopsies for indeterminate strictures was shown in a large multicenter prospective observational study that included 297 patients. The investigators reported an overall sensitivity of 78% for visual inspection alone versus sensitivity of nearly 50% when directed biopsies were obtained. Clinical management was affected in 64% of patients undergoing cholangioscopy. The import of visual inspection has shown reproducibility across systems, with further supporting evidence from literature on the SpyGlass system. One study reported a sensitivity of 85% and specificity of 79% when performing inspection alone using the SpyGlass system. Both sensitivity and specificity were noted to be 82%, respectively, with SpyBite miniforceps for targeted biopsies.
Cholangioscopy is also being explored for the classification of strictures in patient populations with fibroinflammatory biliary disease and anastomotic anatomy such as PSC, IgG4 cholangiopathy, and liver transplant recipients. A prospective study of 53 patients with a dominant stricture on imaging in the context of PSC showed superior efficacy for detecting malignancy when compared with ERCP alone. Superior sensitivity (92% vs 66%), specificity (93% vs 51%), accuracy (93% vs 55%), and both positive (79% vs 29%) and negative predictive values (97% vs 84%) were observed in the cholangioscopy group. A diagnostic role for cholangioscopy in identifying IgG4-mediated disease in patients with a previous diagnosis of PSC is also being explored. An observational study comprising 20 patients following orthotopic liver transplantation showed a role for cholangioscopy in diagnosing ischemic cholangiopathy, anastomotic ulceration, and even retained sutures. Future considerations may further implicate a role for cholangioscopy in the mapping of intraductal tumor spread before surgical resection and even in the evaluation of recurrent pancreatitis of unknown cause.
Adjunct imaging technologies are being paired with cholangioscopy as avenues for enhanced evaluation of biliary epithelium. These modalities include autofluorescence and narrow-band imaging (NBI). Autofluorescence technology highlights abnormal mucosa as black or dark green and is reported to increase the sensitivity of cholangioscopy to nearly 100%; however, this is at the expense of specificity and accuracy. NBI achieves optical color separation by narrowing the bandwidth of transmitted images. Prototype models (Olympus, Center Valley, PA) have been used in various centers as attempts are made to validate its clinical usefulness. One study evaluated both NBI and conventional white light cholangioscopy for 21 biliary lesions. Visualization of intraductal disease such as surface structures and vessel architecture was more often rated excellent when using NBI. These modalities add limited, incremental benefit. Major limitations include poor visualization in the setting of mucus and pus. Also, bile and blood appear similar with NBI. Although there is promise for these modalities in that they may enable the biliary endoscopist to detect early lesions that possess flat, minimally projecting architecture, technology that facilitates evaluation for submucosal abnormalities, proximal disease, and overall provides better magnification is desirable and yet to be realized.
Diagnosis and Management of Choledocholithiasis
Cholangioscopy has emerged as a useful nonsurgical method of achieving stone retrieval in difficult cases and has even been shown to detect residual stones in nearly 30% of patients who have previously undergone mechanical lithotripsy during conventional ERCP.
Intraductal lithotripsy may be required in complicated choledocholithiasis in the setting of failed, traditional ERCP techniques. It is best performed under direct cholangioscopic visualization and the aim is to avoid the complications of bleeding or perforation. Cholangioscopy-directed lithotripsy has a reported success rate of 90% to 100% in various observational studies. The precise technique of intervention varies by endoscopist and expert center. This variability begins even with the cholangioscopic system with SpyGlass, direct choledochoscopy and dual-operator systems reporting similar levels of success and often the need for only 1 session. Universal to effective lithotripsy is a need for sufficient intraprocedural irrigation of the bile duct; late cholangioscopic systems offer the necessary working channels for technical success.
Specific techniques for intracorporeal stone fragmentation include laser ablation and shock wave (electrohydraulic) therapy. Laser lithotripsy is performed using a double-pulse yttrium aluminum garnet (YAG) or holmium laser, which can be directed at difficult stones for fragmentation. A prospective, randomized trial reported that cholangioscopy-directed laser lithotripsy realized a significantly higher rate of stone clearance (97%) than conventional extracorporeal shock wave lithotripsy, with fewer sessions. These findings have been validated in subsequent investigations. No randomized data exist comparing laser lithotripsy and intraductal electrohydraulic lithotripsy under cholangioscopic guidance. Factors that affect the selection of a particular modality largely depend on the training and comfort of the biliary endoscopist with a certain technique. Laser lithotripsy may carry a higher cost and may be more time consuming.
Expanding Therapeutic Applications
Other emerging interventional applications for cholangioscopy include ablative therapy for the management of established, malignant biliary strictures. These applications include cholangioscopy-directed photodynamic therapy, YAG laser ablation, and argon plasma coagulation for management of intraductal tumor growth. Cholangioscopy-assisted biliary access and drainage across complex stricture disease has also been described. In 1 report, intrahepatic duct stent placement was successfully achieved using a 5-mm ultraslim endoscope after repeated attempts during conventional ERCP had failed. Cholangioscopy has also been reported as a modality to facilitate guidewire placement in the presence of severe, complex strictures in both malignant disease as well as in those with a history of liver transplantation. Future considerations may also include a role for cholangioscopy in the assessment and treatment of hemobilia.
Endoscopic ultrasonography
Endoscopic ultrasonography (EUS) is an imaging modality that uses uniquely designed echo endoscopes that possess optical, sonographic, and mechanical properties beyond those of traditional ultrasound transducers and gastrointestinal endoscopes. Since its inception around 30 years ago, EUS has played an important role in staging gastrointestinal and nongastrointestinal malignancies and diagnosing pancreaticobiliary disease and in recent years has been recognized as an important tool for the therapeutic endoscopist. The proximity of the stomach and duodenum to the extrahepatic biliary system has expanded EUS as a useful means of imaging biliary anatomy. The technique of fine-needle aspiration (FNA) offers the potential for tissue sampling to obtain index pathology.
Indeterminate Strictures and Cholangiocarcinoma
The role of EUS in the evaluation of indeterminate strictures is becoming increasingly prominent in the literature. However, there remains controversy regarding its efficacy and best use.
Several studies have reported EUS-guided FNA to be a reasonable modality for the evaluation of indeterminate biliary strictures. Retrospective cohort studies comprising fewer than 25 patients evaluated EUS-FNA for indeterminate strictures, reporting a sensitivity and specificity of 77% to 100% and 100%, respectively. However, these studies stand in contrast to several, larger retrospective studies that show a sensitivity of 45% to 47% Variable results are likely related to the anatomic location of the lesions within the extrahepatic biliary tree. This is best shown in a study by Rosch and colleagues, in which they prospectively compared ERCP brush cytology/forceps biopsy versus EUS-guided FNA for biliary strictures. EUS-FNA was found to be inferior to ERCP in the subgroup of patients with proximal/hilar, biliary tumors (EUS 25% vs ERCP 75%); however, it was superior for distal malignant strictures in the setting of pancreatic mass (EUS 60% vs ERCP 38%).
Promising results were found in a recent meta-analysis of 9 studies, comprising a total of 284 patients, that showed EUS-FNA to have a pooled sensitivity for the diagnosis of biliary strictures of 84% and specificity of 100%. Moreover, significant rate of complications were not reported for EUS-FNA in this setting, suggesting that it is an overall safe modality.
As is to be expected with many imaging modalities, when the pretest probability of malignancy is increased, EUS-FNA seems to have more consistent results. A large single-center prospective study of patients with cholangiocarcinoma showed that EUS (94%) was superior compared with triphasic CT (30%) and magnetic resonance imaging (42%) for tumor detection in patients with available imaging. In terms of diagnostic histopathology, promising data are reported in prospective studies. Two studies with cohorts ranging from 28 to 42 patients found EUS-FNA to be both sensitive and specific for diagnosing suspicious biliary tree lesions, at greater than 86% and 100%, respectively. Positive predictive value, negative predictive value, and diagnostic accuracy for this technique in the context of suspicious lesions for malignancy were 100%, 57%, and 88%. In addition, EUS-FNA for proximal lesions in this context after a previous workup suggestive for malignancy have shown favorable results for yielding a confirmatory diagnosis. In one study, 44 patients with potentially operable hilar strictures concerning for cholangiocarcinoma with previous inconclusive tissue diagnosis underwent EUS-guided FNA. Of these patients, 26 were found to have cholangiocarcinoma, 5 other malignancies, and 12 had benign findings. The accuracy, sensitivity, and specificity were reported as 91%, 89%, and 100%, respectively. Moreover, in a case series of 10 patients with bile duct strictures at the hilum concerning for cholangiocarcinoma, EUS-guided FNA provided adequate material for analysis in 9 patients.
Overall sensitivity of EUS-FNA for diagnosis of indeterminate strictures is variable. It seems that efficacy is greater for distal versus proximal lesions (81% vs 59%, respectively) and in the setting of lesions with higher pretest probability for malignancy.
Choledocholithiasis
In contrast to evaluation of indeterminate strictures and malignant biliary disease, EUS is now established to be a reliable, safe modality for the diagnosis of biliary stone disease ( Fig. 2 ).
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