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Principles of Ultrasound 2. Equipment 3. Training and Simulators 4. Indications, Preparation, and Adverse Effects 5. Mediastinum 6. EUS in Esophageal Cancer 9. Stomach How to perform EUS in the Stomach Subepithelial Lesions Pancreas and Biliary Tree EUS in Pancreatic Tumors Anorectum How to perform Anorectal EUS EUS in Rectal Cancer EUS-guided Tissue Acquisition Interventional EUS If you wish to place a tax exempt order please contact us.
Endoscopic ultrasound EUS is a particular aspect of gastrointestinal ultrasonography, since the miniature transducer is placed at the tip of an endoscope equipped with video optics. Gastrointestinal endosonography began in the mids, was developed in the mids, and is now used in current practice in gastrointestinal oncology, but also in the diagnosis of biliary obstruction and in assessing neoplastic and inflammatory disorders of the pancreas.
Several other less common indications have been developed, for example submucosal tumors of the gut wall, portal hypertension, esophageal motor disorders and assessment of various anorectal and gynecological disorders, in particular deep subperitoneal endometriosis. This imaging technique, which has the highest resolving power currently available for evaluating the digestive tract wall and the organs in contact with it, has undergone a rapid evolution in the last decade with the development of EUS-guided histology, the development of EUS-guided therapeutic techniques and the advent of technological refinements such as elastography and contrast-enhanced EUS.
It is important to bear in mind that this imaging technique, in which the quality of the results depends directly on operator experience, requires considerable investment in terms of diverse, expensive equipment, long specific training except for therapeutic endoscopic ultrasound which is easy for an interventional endoscopist to learn and finally the recruitment of many types of personnel. Its use is therefore justified only at referral centers where all these conditions are met. Although therapeutic endoscopic ultrasound is the most exciting part of the technique, it is not currently in widespread use because of the limited indications and small number of patients who may benefit from it.
The resolving power of an ultrasound probe is directly proportional to the frequency emitted: with a frequency of 7. On the other hand, the depth of field that can be analyzed is inversely proportional to the frequency used Table 1. Table 1 EUS transducer frequency and depth of field. Two types of ultrasound technique are used in endoscopic ultrasound.
Figure 1 Normal gastric wall with five layers. Electronic radial scope. Its main drawback is that it is impossible to carry out EUS-FNA as the path of the needle passes through the plane of the ultrasound image and cannot therefore be monitored in real-time. Because radial imaging is long-established and relatively easy to perform, it currently remains the most widely used EUS technique. Three types of apparatus have been developed as a result:. B Fujinon EUS scopes, radial and linear. C Olympus EUS scopes, radial and linear. Figure 4 Olympus blind probe MH mechanical radial 7.
For the esophagus, use a transnasal or pediatric gastroscope, which can pass through the stenosis without previous dilation.
Endosonography - 4th Edition
Aspirate the air present in the gastric lumen, position a 0. Then advance the probe into the stomach celiac region. The examination is performed by withdrawing the probe under ultrasound control as far as the cervical esophagus. The ultrasound image obtained in electronic B mode is a sagittal image Figs 5 , 6 provided by an electronic transducer. The plane of the image is parallel to the axis of the endoscope. Figure 5 Aorta. Figure 6 Pancreatic cancer located within uncinate process, invading the posterior side of the SMV.
IVC, inferior vena cava. Electronic linear scope. B Pancreatic adenocarcinoma located within the body with involvement of the celiac axis left with EUS-guided FNA right using a Pentax linear scope coupled with a Hitachi console. As a result of this option, therapeutic EUS uses echoendoscopes with a large operating channel. The drawback of this type of equipment is the nature of the sagittal images as these are inappropriate for studying the circumference of the GI tract and thus assessing locoregional involvement prior to treatment or surveying cancers of the GI tract.
Two types of instrument use this technique: video-echoendoscopes and rigid probes. EUS, even if performed without FNA sampling, usually requires intravenous sedation or light general anesthesia because the procedures can be prolonged and require the patient to remain completely still. The use of a benzodiazepine Midazolam may be sufficient for examination of the esophagus, stomach and mediastinum.
Combining this with an opiate or Propofol, to produce short-term general anesthesia may be necessary for pancreaticobiliary examination or for any EUS-FNA, depending on local custom. This means that EUS needs to be performed at centers with appropriate outpatient facilities. In contrast, endorectal or endoanal ultrasound without FNA may be performed without sedation except for painful cancer of the anal canal, or perianal abscess or fistula.
Figure 8 A Position of the patient for pancreaticobiliary examination. B The neutral position of the echoendoscope handle: the front of the handle is facing the patient. C The open position of the echoendoscope handle.
D The closed position of the echoendoscope handle. E The extreme closed position of the echoendoscope handle. Figure 9 Position of the echoendoscope handle for EUS.
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The closed position 3 is the most natural. The extreme closed position 4 is easy to obtain. The neutral position 1 is easy to obtain. The open position 2 is very difficult to sustain for any length of time. Passing from the neutral to the open position has to be very precise.
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This position is used when biopsying the tail or neck of pancreas. The open position 2 is the natural position. The neutral position 1 is very easy to obtain. The closed position 3 is easy to obtain. The extreme closed position 4 is very difficult to sustain for any length of time. Passing from the closed 3 to the extreme closed position 4 has to be very precise. Figure 12 Examination of the rectum and anus. Patient in supine position. The positions of the handle that are used are the neutral 1 and the open positions 2.
EUS examination uses two different methods that are sometimes combined to obtain a satisfactory acoustic window between the transducer and the gut wall, as well as the surrounding region.
Principles, Techniques, Findings
The first is the balloon method, and the second is the instillation of water through the operating channel of the echoendoscope. Water instillation is required for examination of rectal lesions, since this allows the endoscope to reach and pass the rectosigmoid junction where the examination should begin without the need for air instillation, i. The use of deaerated water is particularly useful for villous tumors or superficial cancers.
The miniprobes are introduced into the endoscope operating channel and slid in endoscopic view over the lesion to be studied:. These indications will continue to evolve, especially with advances in oncology, e. The lesions can be located using either radial or linear EUS.
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A balloon is not useful in this setting. Before removing the needle from the sheath, check endoscopically that the sheath around the needle is visible, but only barely visible. Upwards deflection of the scope tip keeps the transducer tip pressed against the wall and creates a shallow exit angle for the needle. The needle is advanced from its sheath and applied against the gut wall at an exit angle pre-determined by the endoscope being used.
The path of the needle towards the target must take account of this predetermined angle making pre-positioning of the echoendoscope in relation to the target essential.
The latest generation Olympus and Pentax echoendoscopes have an elevator and are therefore easier to handle than older echoendoscopes, because the angle of passage through the digestive wall to the target can be adjusted. The Fujinon echoendoscope has a virtual target line Fig. The exit angle of the needle is very shallow and is comparable, without an elevator, to that provided by Olympus and Pentax instruments when used with their elevators. The value of intravenous antibiotic prophylaxis is debatable for solid lesions unless indicated for prevention of infective endocarditis.
Antibiotic prophylaxis is essential for biopsy of a cystic lesion, whether of the pancreas or digestive wall.ecolearning.org.uk/96.php
Practical Endosonography (EUS)
It is also required if the patient is using gastric antisecretory drugs PPI since this type of product encourages gastroduodenal microbial overgrowth. Antibiotic prophylaxis is also required for transrectal FNA. The antibiotic therapy must be continued orally for 3 to 5 days. Once continuous negative pressure has been obtained, the needle should be moved slowly to and fro several about 20 times in the lesion without hurrying, without removing the needle from the lesion, and trying, if possible, to change the angle of penetration of the lesion; this is helped by having an elevator, if the target is small and close to the lesion or if the lesion is soft, which is rare in cancer of the pancreas; if, as is more common in pancreatic cancer, the lesion is large, far from the probe or hard, angulation of the endoscope should be adjusted from up to down angulation to change the path of the needle in the lesion.
The needle must always be monitored in real time on the screen, during these movements, to avoid vascular or organ injury. To be sure that the needle is correctly centered in the lesion during aspiration, make small clockwise and anti-clockwise movements of the handle. Avoid penetrating any vascular and particularly arterial structures which may be present between the digestive wall and the target.