EUS was first introduced 20 years ago. Currently, it continues to play a main role in the evaluation of the biliary system. The biliary examination can be performed with a radial echoendoscope (perpendicular scanning plane to the echoendoscope axis) or with a linear-array echoendoscope (parallel scanning plane to the echoendoscope axis). Linear EUS produces images that are less familiar than those of radial EUS; particularly, it may be difficult to obtain long views of the bile duct. Thus, linear scanners have not been used in a routine way in many centers for diagnostic EUS in bile-duct lesions. During the last 15 years, a number of studies, most of them evaluating radial EUS, analyzed the issue of EUS for the diagnosis of biliary obstruction and showed comparable performances with ERCP, the previous criterion standard testing. However, linear-array echoendoscope allows EUS-guided FNA (EUS-FNA), which can increase the diagnostic accuracy of EUS in biliary strictures with very small risk. In addition to EUS-FNA, therapeutic EUS indications for biliary-tree lesions have emerged, eg, bile-duct drainage. This has led to changing trends in EUS equipment use. Although evidence shows that the use of linear-array echoendoscope has increased in the evaluation of biliary diseases, few data are available about the diagnostic performances of linear EUS in this field.
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