Thomas J. Savides1 and Frank G. Gress2 1 University of California, San Diego, CA, USA 2 Mount Sinai Medical Center, New York, NY, USA EUS is difficult to learn for several reasons. There are new cognitive skills regarding anatomy and disease states, there are endoscopic technical skills to master, and there are ultrasound concepts to learn. Most importantly from a cognitive viewpoint, gastroenterologists usually are not trained to understand extraintestinal three‐dimensional anatomy. This needs to be mastered before attempting to understand the EUS imaging of these areas. Additionally, much of EUS is related to the diagnosis, staging, and treatment of cancer, which is not taught in depth during fellowship [1–9]. Endosonographers must understand the diagnosis and management of gastrointestinal, pancreaticobiliary, and thoracic malignancy at a level where they can communicate effectively with medical and surgical oncologists. They must also have sufficient knowledge of cytology and pathology to maximize diagnostic yield with their pathologists. From an endoscopic technical point of view, endoscopic ultrasound equipment is quite different than standard endoscopes, with extra buttons, balloons, and ultrasound processors to master. The scopes are often larger, with greater outer diameters and longer bending sections at the tip, and with oblique viewing, which makes scope passage and manipulation more difficult than standard endoscopes. These larger, stiffer scopes also may increase the risk of complications, such as perforation, if not used carefully. After learning how to handle the instruments and maneuver them, trainees must acquire dexterity with the fine adjustments in scope position necessary to bring the ultrasound image into focus. Another major challenge is that endoscopists now need to learn the fundamentals of ultrasound imaging. This is not taught during GI fellowship. Specifically, trainees need to understand ultrasound physics, impact of imaging frequency on resolution, and depth of penetration, characteristics of various tissue structures (i.e., air, fluid, blood, soft tissue, and bone), as well as imaging artifacts [10, 11]. A number of skill sets will be described, which are needed to learn EUS (Table 7.1). To master these skill sets, one needs a variety of learning tools. These tools include textbooks, instructional videos, attending national, regional, and local courses, internet websites, observing experts, or performing formal training at a center of excellence in advanced endoscopy. Table 7.2 lists a number of these resources for self‐study. Note that these training resources constantly change over time, but provide a good base from which to start training. In addition, some GI societies such as the American Society for Gastrointestinal Endoscopy (ASGE) post and update a comprehensive list of advanced endoscopy training programs on their websites. In addition, ASGE sponsors the advanced endoscopy match. Information on the match is available on the ASGE website (Source: American Society for Gastrointestinal Endoscopy Website: www.asge.org). While there is no single way to learn anything, EUS learners need to focus on the core skill sets required for successful performance of EUS. The trainee should generally learn this in a sequential order, although simultaneous learning often occurs. These skills can be learned using a variety of sources such as textbooks, training videos, short courses, and mentored training [10, 11]. This must be reviewed in detail prior to learning the EUS imaging of anatomy. This is best done by reviewing anatomy textbooks. Special attention is given toward the structures immediately adjacent to the luminal gastrointestinal tract, as this is what will be visualized with EUS. More recently, there have been anatomy textbooks and training software created based on digitalized human sections, such as from the Center for Human Simulation at the University of Colorado (www.uchsc.edu). Most importantly, the anatomy must be learned in such a way that the relationship of one structure to another is appreciated, both in cross‐sectional as well as oblique viewing (as would occur with varying imaging planes in EUS) [10]. Table 7.1 Key skill sets for learning EUS. Table 7.2 Resources for learning EUS. Trainees should learn about the indications for EUS and specifically the different disease states for which EUS is applied, and how EUS impacts not only the diagnosis, but also treatment and follow‐up. These include the broad areas of malignancy (e.g., esophageal, gastric, pancreatic, rectal, anal, lung cancers), benign pancreaticobiliary diseases (i.e., stones, obstruction, cysts, pancreatitis), luminal and extraluminal masses (subepithelial masses, peri‐intestinal cysts), and disorders of the intestinal musculature (anal sphincters, lower esophageal sphincter, pylorus, fistulas and abscesses, etc.). This learning is usually done with textbooks of gastroenterology, oncology, surgery, endosonography, as well as Web‐based resources. In addition, attending hospital Tumor Boards and GI/Surgery conferences is a very valuable learning resource for clinical correlation and to understand how different disease states are managed by referring physicians. Ultrasound principles can be learned using a textbook of ultrasonography, as well as video instruction. This is usually addressed in dedicated EUS textbooks [10,12–14]. Initial focus is on understanding ultrasound principles and artifacts. There are courses on ultrasound for nonradiologists, and they can also be very useful (such as for imaging the liver) for learning the basics. Finally, spending some time with an ultrasound technician or radiologist as they perform and interpret ultrasound images can be very helpful to understand basic principles and to start applying this to learning the EUS anatomy from the transabdominal percutaneous approach [9]. Learning EUS image interpretation is the most important and lengthy part of learning. This is a cognitive skill of pattern recognition and not a technical endoscopic skill. Initially, this should be done by reading EUS textbooks and studying EUS training videos (such as from the ASGE) [9]. EUS computer simulators have been created to assist in this training step, but these are still investigational and very few exist [11]. EUS interpretation is best learned by watching an experienced endosonographer, either one‐on‐one as the endosonographer does cases or via video or live‐demonstration courses. The goal here is to see large numbers of cases since images vary based on pathology, normal variants, and patient issues such as prior surgery and body habitus. Learning EUS is a two‐step process: interpreting images and endoscopic manipulation. When learning at this stage, the trainee should always be trying to identify different structures seen on the screen and ask the mentor to confirm if correct. It is critical at this point to start understanding relational anatomy, for example, if you see the confluence of the portal vein and superior mesenteric vein, you should also expect to see the superior mesenteric artery. The instructor can help in teaching here by quizzing the trainee on different anatomical structures and by highlighting the importance of having a routine in terms of visualizing structures. Different instructors use different concepts (i.e., “stations,” “pull‐back method,” “push method”), but the general concept is that one wants to have a standardized approach to visualize all the anatomy. Learning how to operate the EUS equipment is the next stage. This first involves learning to understand the scope and processor anatomy. Understanding the scope requires learning how the air and water buttons differ from standard endoscopes, and how to place a balloon on the tip and how to fill the balloon with water. It is also important to understand how to utilize the ultrasound processor to obtain optimal images, by using different presets, imaging frequencies, gain, magnification, Doppler flow, and labeling. This should also include troubleshooting common problems such as no image on the screen, poor image quality, or settings/buttons unintentionally changed during wiping down of the ultrasound processor surface during room turn over. These skills can be taught by endosonography mentors, GI nurses/technicians, and equipment company representatives. Initially, the equipment inservicing should be taught outside the patient’s body. The trainee can be shown the parts of the scope and asked to try using various buttons (i.e., inflate and deflate scope tip balloon). The scope can then be placed into a water‐filled container that contains gauze to show how the image can be identified, how to troubleshoot, and to show how to manipulate the ultrasound processor settings to enhance imaging. This can also be done in a plastic or porcine model. Learning to pass the EUS scope through a patient’s mouth, intubate the esophagus, and position it properly for EUS imaging ideally requires one‐on‐one training with a mentor. Because the scopes are larger and stiffer, care must be taken in passing the scope through the mouth, the lower esophageal sphincter, and the pylorus/duodenal sweep in order to avoid trauma. Sometimes, these skills can be learned outside the body by manipulating the scope in a training model such as an ex vivo simulator or pig stomach [15]. We will discuss simulator models later on in the chapter. Initially, this skill should be taught in a well‐sedated patient. It is important to emphasize to the trainee not to push with force if resistance is met. If there is resistance, then the trainer should take the scope to feel why there is resistance and instruct how to resolve the problem. Often, this is just a matter of repositioning the scope or inflating the balloon slightly. Diagnostic imaging is learned once the scope is in place and can be easily manipulated. Skills to be learned at this point also include how and when to inflate water into the transducer balloon, as well as removal of air and placement of water within the lumen to optimize ultrasound imaging. Instruction must also include where and how to place the transducer for imaging and includes patient positioning (i.e., lateral, prone, supine, head of bed elevated). This should include learning the appropriate maneuvers for obtaining the necessary images for disease‐specific indications; for example, if evaluating for a pancreatic mass, one needs to visualize the pancreas parenchyma, pancreatic duct, common bile duct, liver, and peripancreatic blood vessels and lymph nodes. Considerable time is required to master this skill set, as one needs to get comfortable in a variety of disease‐specific conditions, patient body habitus states, and sedation levels. Additional time is also needed to become familiar with and ultimately learn to use all available EUS equipment including both radial and linear EUS echoendoscopes and catheter‐based ultrasound probes. There is no consensus on whether both linear and radial should be introduced at the onset together or should the trainee master one before starting with the other. When the trainee initially is learning at this point, emphasis should just be on examining limited areas with EUS. For example, starting with the easiest things such as finding the aorta or gallbladder, then progressing to identifying the pancreas, and finally to visualizing the common bile duct. A balance must be found between expediting the patient’s exam and trainee learning time. Usually, the fellow should have short amounts of time to find structures so as not to significantly prolong the sedation for the patient. It is important for the fellow to realize that during this learning phase, not every structure needs to be visualized. As the fellow progresses in ability, emphasis should focus on identifying the pertinent anatomy related to the disease state (such as examining the left adrenal gland in a patient with mediastinal adenopathy and suspected lung cancer). Once the trainee can reliably identify pertinent normal structures as well as pathology (diagnostic EUS), then, and only then, EUS‐guided FNA can be learned. It is critical to have a good understanding of normal and abnormal EUS findings, because one needs to understand which lesions should and should not undergo EUS FNA. Additionally, the trainee needs to understand the risks associated with FNA and when to administer prophylactic antibiotics, such as with pancreatic cysts and possibly during EUS‐guided celiac plexus block procedures. One must also learn the differences between EUS FNA needle systems including the different‐sized and designed needles (19, 22, and 25 gauge needles, the celiac plexus needle, etc.) and when to use one versus the other. Needle preparation must be learned. One must also learn how to safely advance the needle through the EUS scope’s working channel without puncturing the channel, how to adjust the sheath length, how to use the elevator, and what to do if the needle does not come out of the scope tip (deflect the scope tip down). Once these skills are mastered, one can learn to puncture a lesion under EUS guidance, remove the stylet, utilize suction if indicated, and move the needle in and out through the lesion in parts, which have the highest yield for diagnostic material. Perhaps, most important is learning and understanding not only when to do FNA, but when not to do FNA, such as for obvious mediastinal cysts (which can get infected) or for peritumoral lymph nodes that can only be reached by passing the needle through intervening tumor (risk of seeding a benign lymph and getting a false‐positive cytology). Learning how to do EUS FNA can be done with EUS textbooks and videos, as well as using phantom models, simulators, porcine models, or under direct mentorship during live patient cases.
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Endoscopic Ultrasound
EUS requires different skill sets than standard endoscopy
Learning resources for EUS
The skill sets needed to learn EUS
Anatomy
Endoscopic Ultrasound textbooks:
Gress and Savides. Endoscopic Ultrasonography, Wiley, 2016
Gress and Savides. Atlas of Endoscopic Ultrasonography, Wiley, 2011
Hawes, Fockens and Varadarajulu. Endosonography, Elsevier, 2019
Bhutani and Deutsch. Digital Human Anatomy and Endoscopic
Ultrasonography, Peoples’ Medical Publishing House, 2004.
Dietrich. Endoscopic Ultrasound, Thieme, 2006.
EUS Phone App
EUS – Diagnostic and Interventional Endoscopic Ultrasound (Varadarajulu, Fockens, Hawes)
EUS Training Videos
American Society for Gastrointestinal Endoscopy Learning Library
Industry created training videos
Local Hospital Conferences
Tumor Board
Medical–Surgical Conference
GI Pathology Conference
Radiology Conference
National Courses
ASGE Diagnostic EUS Training Program (Application process & Acceptance required) – year long
ASGE EUS courses (1–2 days)
Understand diseases and conditions assessed with EUS
Ultrasound principles
EUS image interpretation
How to operate EUS equipment
Use of EUS scope
Diagnostic EUS imaging
EUS‐guided fine‐needle aspiration (FNA)
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