Endoscopic ultrasound: moving from diagnostics to therapeutics

Endoscopic ultrasound was initially introduced in the 1980s as a diagnostic modality using echoendoscopes with radial scanning that permitted reconstruction of cross-sectional images similar to computed tomography The close proximity of the ultrasound transducer to the gastrointestinal wall and retroperitoneal structures allowed a detailed examination that is not possible with cross-sectional imaging such as computed tomography and magnetic resonance imaging. It proved to be highly accurate and useful in the staging of gastrointestinal malignancies, as well as in characterizing the nature of subepithelial lesions and disorders of the pancreaticobiliary system. The introduction of linear echoendoscopes facilitated fine needle aspiration because, with linear scanning, it was able to trace the path of the tip of the needle during the puncture process. In addition to being very useful for tissue acquisition for diagnostic purposes, the principles behind endoscopic ultrasound-guided fine needle aspiration paved the way for the development of therapeutic endoscopic ultrasound. Substances could now be delivered by endoscopic ultrasound into targeted areas, an example being an endoscopic ultrasound-guided celiac plexus block and neurolysis. In addition, the endoscopic ultrasound-guided puncture of fluid collections, abscesses and obstructed biliary and pancreatic ductal systems facilitated the passage of guidewires, thus allowing therapeutic drainage procedures to be performed using the Seldinger technique. This review summarizes the diagnostic capability of endoscopic ultrasound and then moves on to elaborate in detail its therapeutic capability and potential.