Applications of Endoscopic Ultrasonography

, and , Harbor-UCLA Medical Center, Torrance, California.

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Acquiring Technical Proficiency

Prior to performing EUS, competency in upper endoscopy is required. EUS is more difficult than conventional endoscopy, because the EUS endoscope has a forward-oblique or side-viewing optic similar to that of duodenoscopes used in endoscopic retrograde cholangiopancreatography (ERCP) and also because the rigid portion of the endoscope tip is longer than it is on conventional upper endoscopes. This design increases the risk of perforation, especially if the instrument is advanced from the stomach into the descending duodenum. Experience in transabdominal ultrasound is helpful in this setting because it introduces the examiner to the echostructures located in the abdomen, such as the liver, spleen, pancreas, kidneys, and intra-abdominal vessels. At our institution, transabdominal ultrasound is routinely performed prior to EUS to obtain an overview.

According to the American Society of Gastrointestinal Endoscopy,[7] luminal endosonography requires 3-6 months' experience to establish competency, whereas pancreaticobiliary EUS and FNA may require up to 1 year of intensive training. Fockens and coworkers[8] reported their experience training in endosonographic staging of esophageal cancer. Their study suggested that 100 procedures were required before one would reach an acceptable level of accuracy for staging esophageal cancer. Additionally, results of a multicenter study by Hoffman and associates[9] suggested that with intensive hands-on experience in a facility performing a high volume of EUS procedures, a trainee could become competent to perform EUS within a relatively short period of time. That is, for example, they report that the number of procedures needed to successfully visualize pancreatic head were 34; pancreatic body and tail, 26; and to interpret pancreatic pathology, 60.

The first EUS examination should be done under close guidance by an experienced endoscopic ultrasonographer. Participation in EUS courses with hands-on application offered by selected centers throughout the United States greatly facilitates gaining competency in this technique. At our institution, we also offer annual EUS training courses as well as specially arranged individual training under close supervision of experienced endoscopic endosonographers.