Intraductal endosonography (IDUS) of biliary tree and pancreas is a method which extend and make more accurate diagnostic measures of pathologic processes of extrahepatic biliary tree, main pancreatic duct with surrounding tissue, but is also useful for tight eosophageal strictures et c. The advantage of this method is a small calibre of the probe which is able to introduce through the endoscope channel and its high working frequency (20 MHz and more). We can through the leading wire carefully introduce the probe into biliary tree and pancreas. On the basis of detailed image of ultrasound changes in structure, width and wall outline we can asses the characteristic of pathology process, locoregional expansion and by this to contribute to the differentiation of benign or malignant cause of stenosis, but, unfortunately, this method is not able to establish a histopathologic diagnosis. The method is useful mostly in cases where ERCP, CAT scan and normal endosonography ultrasound investigation are not able to explain the real cause of stenosing processes of biliary or pancreatic ducts.

        Key words: intraductal endosonography – diagnosis of disease of the biliary tree