Biliary Endoscopy
Biliary Endoscopy
The literature this year contained a number of articles reviewing the different methods of biliary drainage for malignant obstruction, highlighting approaches to unilateral drainage, and stressing the risks of incomplete drainage after contrast injection. A number of articles addressed issues surrounding the differentiation of benign and malignant biliary strictures.
Distinguishing malignant from benign biliary strictures remains difficult. Although both have characteristic features, they are not specific enough to determine the exact type of stricture. Brushing samples for cytology have poor yields. Intraductal ultrasound (IDUS) appears to be an evolving modality to aid in diagnosing pancreaticobiliary disease. Previous reported accuracy of IDUS for differentiating benign from malignant strictures ranges from 76% to 89%. IDUS has several advantages over standard imaging modalities. High frequency sound waves provide high spatial resolution images enabling assessment of malignant infiltration in ducts as well as surrounding vascular structures. While it allows for greater distinction between structures, it does have its limitations. At times the gallbladder is difficult to illuminate. In addition, it is only available in a few centers and each probe is over $5000 and have limited useful lives. Furthermore, in contrast to ERC, intraductal ultrasound cannot visualize intrahepatic ducts and due to its shallow depth of penetration, it has a limited ability to image lymph nodes.
Farrell et al evaluated the yield of this technique in biliary strictures. Sixty-two patients underwent intraductal ultrasound as well as endoscopic retrograde cholangiopathy. ERC and tissue sampling with intraductal ultrasound identified 28/31 malignant strictures and 27/29 benign strictures with a sensitivity of 90% and a specificity of 93%. The study demonstrated intraductal ultrasound to be a useful adjunct to ERC tissue sampling. The study demonstrated the niche ability of intraductal ultrasound to aid in the diagnosis of Mirizzi's syndrome. Three out of four cases were correctly diagnosed.
Moon et al focused on Mirizzi syndrome-like features (extrinsic duct obstruction) in their study of wire guided intraductal ultrasound. Preoperative diagnosis impacts surgical intervention decisions. Diagnosis by conventional imaging such as ultrasound or CT scan is limited because of the close proximity of the cystic and common hepatic ducts. Proximal CHD visualization by EUS is often difficult. Sixteen patients underwent intraductal ultrasound with subsequent surgery for possible extrinsic compression and nonvisualization of the gallbladder on ERC. Intraductal ultrasound demonstrated the underlying extraluminal cause of the stricture in 14/16 cases. Intraductal ultrasound was able to discern this syndrome from other causes of common hepatic duct compression with high accuracy.
In a separate study, Vazquez-Sequeiros et al evaluated the potential additive benefit of intraductal ultrasound in bile duct stricture analysis. Based on a retrospective blinded review the diagnosis by ERCP was correct in 67% of patients, by tissue sampling in 68%, by combining ERCP with tissue sampling in 67%, and by intraductal ultrasound in 90% of cases. No complications for intraductal ultrasound or ERCP were recorded and intraductal ultrasound added approximately ten minutes to ERCP time. Due to the independent rate of correct diagnosis (benign or malignant stricture), the authors concluded that intraductal ultrasound could improve the ability of ERCP to distinguish benign from malignant biliary strictures. However, two false negative adenocarcinoma diagnoses were obtained by IDUS, ERCP, and tissue sampling, as well as a single false positive for primary sclerosing cholangitis. Due to the retrospective nature of the study, it may be less representative of actual clinical practice and was done at a tertiary referral center where there may be an inherent bias towards the diagnosis of malignancy.
There have been recent significant technical advances in 3-D ultrasound systems. In these systems, multislice ultrasound images are acquired, converted to digital images, and then reconstructed into a 3D moving image that can be manipulated interactively. While MRCP provides a direct view of the biliary tree, its drawbacks include its high cost and its inability to be used in patients with claustrophobia or implanted ferromagnetic devices. Hunerbein et al employed this technique in their evaluation of 40 patients with suspected malignant obstruction. All patients underwent direct cholangiography (with ERCP or PTC) and MRCP. Results demonstrated that the accuracy of MRCP in the evaluation of malignant biliary obstruction was comparable with that of direct cholangiography. The study demonstrated limits and strengths of ERCP (used as the gold standard) and 3D ultrasound imaging. While three-dimensional ultrasound overestimated the extent of stricture in 3 patients, ERCP failed to demonstrate relevant parts of the intrahepatic ducts in two patients with advanced Klatskin-type tumors. MRCP had difficulty with diagnosing tumor extension into the IHD.
This study concluded that three-dimensional ultrasound cholangiography might be a new method of screening patients with suspected biliary obstruction. Rosch et al demonstrated the limited role of sole MRCP in biliary stricture diagnosis, which may allow for the use of 3-D ultrasound in this setting. The current study found that a combination of MRCP and EUS improve the ability to correctly diagnose benign stricture. Interestingly, Textor et al demonstrated that three-dimensional MRCP had comparable diagnostic accuracy to ERCP, albeit solely in patients with PSC.
The literature this year contained a number of articles reviewing the different methods of biliary drainage for malignant obstruction, highlighting approaches to unilateral drainage, and stressing the risks of incomplete drainage after contrast injection. A number of articles addressed issues surrounding the differentiation of benign and malignant biliary strictures.
Distinguishing malignant from benign biliary strictures remains difficult. Although both have characteristic features, they are not specific enough to determine the exact type of stricture. Brushing samples for cytology have poor yields. Intraductal ultrasound (IDUS) appears to be an evolving modality to aid in diagnosing pancreaticobiliary disease. Previous reported accuracy of IDUS for differentiating benign from malignant strictures ranges from 76% to 89%. IDUS has several advantages over standard imaging modalities. High frequency sound waves provide high spatial resolution images enabling assessment of malignant infiltration in ducts as well as surrounding vascular structures. While it allows for greater distinction between structures, it does have its limitations. At times the gallbladder is difficult to illuminate. In addition, it is only available in a few centers and each probe is over $5000 and have limited useful lives. Furthermore, in contrast to ERC, intraductal ultrasound cannot visualize intrahepatic ducts and due to its shallow depth of penetration, it has a limited ability to image lymph nodes.
Farrell et al evaluated the yield of this technique in biliary strictures. Sixty-two patients underwent intraductal ultrasound as well as endoscopic retrograde cholangiopathy. ERC and tissue sampling with intraductal ultrasound identified 28/31 malignant strictures and 27/29 benign strictures with a sensitivity of 90% and a specificity of 93%. The study demonstrated intraductal ultrasound to be a useful adjunct to ERC tissue sampling. The study demonstrated the niche ability of intraductal ultrasound to aid in the diagnosis of Mirizzi's syndrome. Three out of four cases were correctly diagnosed.
Moon et al focused on Mirizzi syndrome-like features (extrinsic duct obstruction) in their study of wire guided intraductal ultrasound. Preoperative diagnosis impacts surgical intervention decisions. Diagnosis by conventional imaging such as ultrasound or CT scan is limited because of the close proximity of the cystic and common hepatic ducts. Proximal CHD visualization by EUS is often difficult. Sixteen patients underwent intraductal ultrasound with subsequent surgery for possible extrinsic compression and nonvisualization of the gallbladder on ERC. Intraductal ultrasound demonstrated the underlying extraluminal cause of the stricture in 14/16 cases. Intraductal ultrasound was able to discern this syndrome from other causes of common hepatic duct compression with high accuracy.
In a separate study, Vazquez-Sequeiros et al evaluated the potential additive benefit of intraductal ultrasound in bile duct stricture analysis. Based on a retrospective blinded review the diagnosis by ERCP was correct in 67% of patients, by tissue sampling in 68%, by combining ERCP with tissue sampling in 67%, and by intraductal ultrasound in 90% of cases. No complications for intraductal ultrasound or ERCP were recorded and intraductal ultrasound added approximately ten minutes to ERCP time. Due to the independent rate of correct diagnosis (benign or malignant stricture), the authors concluded that intraductal ultrasound could improve the ability of ERCP to distinguish benign from malignant biliary strictures. However, two false negative adenocarcinoma diagnoses were obtained by IDUS, ERCP, and tissue sampling, as well as a single false positive for primary sclerosing cholangitis. Due to the retrospective nature of the study, it may be less representative of actual clinical practice and was done at a tertiary referral center where there may be an inherent bias towards the diagnosis of malignancy.
There have been recent significant technical advances in 3-D ultrasound systems. In these systems, multislice ultrasound images are acquired, converted to digital images, and then reconstructed into a 3D moving image that can be manipulated interactively. While MRCP provides a direct view of the biliary tree, its drawbacks include its high cost and its inability to be used in patients with claustrophobia or implanted ferromagnetic devices. Hunerbein et al employed this technique in their evaluation of 40 patients with suspected malignant obstruction. All patients underwent direct cholangiography (with ERCP or PTC) and MRCP. Results demonstrated that the accuracy of MRCP in the evaluation of malignant biliary obstruction was comparable with that of direct cholangiography. The study demonstrated limits and strengths of ERCP (used as the gold standard) and 3D ultrasound imaging. While three-dimensional ultrasound overestimated the extent of stricture in 3 patients, ERCP failed to demonstrate relevant parts of the intrahepatic ducts in two patients with advanced Klatskin-type tumors. MRCP had difficulty with diagnosing tumor extension into the IHD.
This study concluded that three-dimensional ultrasound cholangiography might be a new method of screening patients with suspected biliary obstruction. Rosch et al demonstrated the limited role of sole MRCP in biliary stricture diagnosis, which may allow for the use of 3-D ultrasound in this setting. The current study found that a combination of MRCP and EUS improve the ability to correctly diagnose benign stricture. Interestingly, Textor et al demonstrated that three-dimensional MRCP had comparable diagnostic accuracy to ERCP, albeit solely in patients with PSC.
